WO2020129157A1 - Power conversion device - Google Patents

Power conversion device Download PDF

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Publication number
WO2020129157A1
WO2020129157A1 PCT/JP2018/046577 JP2018046577W WO2020129157A1 WO 2020129157 A1 WO2020129157 A1 WO 2020129157A1 JP 2018046577 W JP2018046577 W JP 2018046577W WO 2020129157 A1 WO2020129157 A1 WO 2020129157A1
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WO
WIPO (PCT)
Prior art keywords
power conversion
voltage
conversion circuit
power
capacitor
Prior art date
Application number
PCT/JP2018/046577
Other languages
French (fr)
Japanese (ja)
Inventor
大斗 水谷
貴昭 ▲高▼原
Original Assignee
三菱電機株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by 三菱電機株式会社 filed Critical 三菱電機株式会社
Priority to JP2019512015A priority Critical patent/JP6523592B1/en
Priority to PCT/JP2018/046577 priority patent/WO2020129157A1/en
Publication of WO2020129157A1 publication Critical patent/WO2020129157A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac

Definitions

  • the present invention relates to a power conversion device having at least three power conversion circuits.
  • a power converter is used that insulates the power supplied from the AC power supply, converts it to DC power, and supplies it to the load.
  • a power converter is generally a power conversion circuit (AC/DC converter) that converts AC power into DC power, and converts the DC power into DC power of a desired size using an insulating transformer.
  • a power conversion circuit isolated DC/DC converter
  • a power conversion device may be configured by two power conversion circuits, that is, a power conversion circuit (DC/DC converter) that converts electric power into a certain DC power and an insulating DC/DC converter.
  • a power conversion device When configuring a power conversion device with two power conversion circuits in this way, if the output voltage is controlled over a wide range, there is a problem that the loss of the insulation type DC/DC converter increases. Therefore, it is considered that a power conversion device is configured by three power conversion circuits connected in series by adding a power conversion circuit to the output side of the insulating converter (see, for example, Patent Document 1).
  • the power supply device described in Patent Document 1 includes an AC/DC converter, an insulating DC/DC converter, and a bidirectional DC/DC converter that are connected in series.
  • the AC/DC converter converts an AC voltage from an AC power source and outputs a DC voltage.
  • the insulation type DC/DC converter converts the DC voltage output from the AC/DC converter and outputs a link voltage.
  • the bidirectional DC/DC converter adjusts the value of the link voltage output from the isolated DC/DC converter, and gives the adjusted link voltage to the battery. Smoothing capacitors are respectively connected between the AC/DC converter and the isolated DC/DC converter, and between the isolated DC/DC converter and the bidirectional DC/DC converter.
  • the present invention has been made to solve the above problems, and an object thereof is to obtain a power conversion device capable of preventing the occurrence of overcurrent at the start of operation.
  • a power conversion device converts a voltage from an input power source into a DC voltage and outputs a converted DC voltage, and a first power conversion circuit via a first DC bus.
  • a second power conversion circuit that is connected to the circuit, transforms the DC voltage output from the first power conversion circuit, and outputs the transformed DC voltage; and second power conversion via a second DC bus bar.
  • a third power conversion circuit connected to the circuit for converting the DC voltage output from the second power conversion circuit and outputting the converted DC voltage to the load; and a first power conversion circuit connected to the first DC bus.
  • the second DC capacitor connected to the second DC bus, and the first, second, and third power conversion circuits start to operate in stages, and the voltage of the first DC capacitor becomes After the first threshold voltage is reached and the voltage of the second DC capacitor reaches the second threshold voltage, the first power conversion circuit outputs power to the load so that the first power conversion circuit outputs the power to the load.
  • the control part which controls the power converter circuit of 3 is provided.
  • the operations of the first, second, and third power conversion circuits are started in stages, so that the voltages of the first and second DC capacitors can be individually controlled. Therefore, it is possible to prevent the occurrence of overcurrent.
  • FIG. 1 is a schematic diagram showing a schematic configuration of a power supply system including a power conversion device according to a first embodiment. It is a figure which shows the specific circuit structural example of the power converter device which concerns on Embodiment 1. It is a figure which shows the specific circuit structural example of the power converter device which concerns on Embodiment 1.
  • FIG. 4 is a diagram for explaining an initial operation of the power conversion device when a resistive load is used as a load in the first embodiment.
  • FIG. 6 is a diagram for describing a first example of an initial operation of the power conversion device when a voltage source load is used as a load in the first embodiment.
  • FIG. 5 is a diagram for describing a second example of the initial operation of the power conversion device when the voltage source load is used as the load in the first embodiment.
  • FIG. 9 is a diagram for describing a third example of the initial operation of the power conversion device when the voltage source load is used as the load in the first embodiment. It is a figure which shows the modification of the power converter device which concerns on Embodiment 1. It is a figure which shows the other modification of the power converter device which concerns on Embodiment 1. It is a figure which shows the specific circuit structural example of the power converter device which concerns on Embodiment 2.
  • FIG. 9 is a diagram for explaining an initial operation of the power conversion device according to the second embodiment. It is a figure which shows the example in which the at least one part function of a control part is implement
  • FIG. 1 is a schematic diagram showing a schematic configuration of a power supply system including a power conversion device according to a first embodiment of the present invention.
  • the same or similar components are designated by the same reference numerals.
  • the power supply system includes a power conversion device 100, an input power supply 1 and a load 7.
  • the power conversion device 100 includes a first power conversion circuit 2, a first DC capacitor 3, a second power conversion circuit 4, a second DC capacitor 5, a third power conversion circuit 6 and a control unit 8.
  • One end (input terminal) of the first power conversion circuit 2 is connected to the input power supply 1.
  • One end (input terminal) of the second power conversion circuit 4 is connected to the other end (output terminal) of the first power conversion circuit 2.
  • One end (input terminal) of the third power conversion circuit 6 is connected to the other end (output terminal) of the second power conversion circuit 4.
  • the other end (output terminal) of the third power conversion circuit 6 is connected to the load 7.
  • the first power conversion circuit 2 converts the voltage from the input power supply into a DC voltage.
  • the second power conversion circuit 4 transforms the DC voltage from the first power conversion circuit 2 through an insulation transformer.
  • the third power conversion circuit 6 converts the DC voltage from the second power conversion circuit 4 and outputs it to the load 7.
  • the first DC capacitor 3 is connected between a pair of first DC buses 31 that connect the first power conversion circuit 2 and the second power conversion circuit 4, and the second DC capacitor 5 is It is connected between a pair of second DC buses 51 that connect the second power conversion circuit 4 and the third power conversion circuit 6.
  • the control unit 8 can control all of the first to third power conversion circuits 2, 4, and 6, and controls each switching element included in each power conversion circuit. In this case, the control unit 8 transmits a drive signal to each switching element included in all power conversion circuits, based on a part or all of detection results obtained from a current detector and a voltage detector described later, A desired operation is realized by controlling ON/OFF of the switching element.
  • the input power supply 1 is an AC power supply such as a commercial AC system or a private generator, or a DC power supply such as a battery.
  • the load 7 is a resistance load or a voltage source load.
  • the resistive load is a load that does not spontaneously generate a voltage, and is, for example, a lighting device or a temperature control device.
  • the voltage source load is a load that spontaneously generates a voltage, and is, for example, a high-voltage battery for vehicle running or a lead battery of vehicle electrical equipment. It goes without saying that the input power supply 1 and the load 7 are not limited to these examples.
  • FIGS. 2 and 3 are diagrams showing a specific circuit configuration example of the power conversion apparatus 100 according to the first embodiment.
  • an AC power supply is used as the input power supply 1.
  • a resistive load is used as the load 7
  • a voltage source load is used as the load 7.
  • the configuration of the power conversion device 100 is the same in the example of FIG. 2 and the example of FIG. 3.
  • the power conversion device 100 includes an AC/DC converter 20 that controls an input current to a high power factor as the first power conversion circuit 2, and a DC voltage as the second power conversion circuit 4.
  • An insulating DC/DC converter 40 that transforms is included, and a non-insulating DC/DC converter 60 that transforms a DC voltage is included as the third power conversion circuit 6.
  • the AC/DC converter 20 corresponds to a PFC (Power Factor Correction) that improves the power factor.
  • the first power conversion circuit 2 (AC/DC converter 20) shown in FIGS. 2 and 3 includes switching elements 21 to 24 and power factor improving AC reactors 215 and 216.
  • the switching elements 21 to 24 are connected in a full bridge type.
  • One end of the AC reactor 215 is connected to the AC power supply 11, and the other end is connected to a connection point between the switching element 21 and the switching element 22.
  • one end of the AC reactor 216 is connected to the AC power supply 11, and the other end is connected to a connection point between the switching element 23 and the switching element 24.
  • the AC reactors 215 and 216 are connected to both sides of the AC power supply 11, respectively, but may be connected to only one side. That is, only one of AC reactors 215 and 216 may be used.
  • the first power conversion circuit 2 shown in FIGS. 2 and 3 has a configuration in which switching elements are used for all semiconductor elements, but is a semi-bridgeless type or totem pole using passive semiconductor elements such as diodes. It goes without saying that it may be a mold configuration.
  • the second power conversion circuit 4 (insulation type DC/DC converter 40) shown in FIGS. 2 and 3 includes an insulation transformer 49, a primary side conversion circuit 4A and a secondary side conversion circuit 4B.
  • Isolation transformer 49 includes two windings that are magnetically coupled to each other. One winding of the isolation transformer 49 is connected to the terminal of the primary side conversion circuit 4A, and the other winding is connected to the terminal of the secondary side conversion circuit 4B.
  • the winding connected to the terminal of the primary side conversion circuit 4A is referred to as a primary side winding
  • the winding connected to the terminal of the secondary side conversion circuit 4B is referred to as a secondary side winding.
  • the primary side conversion circuit 4A includes switching elements 41 to 44.
  • the switching elements 41 to 44 are connected in a full bridge type.
  • the DC side terminal of the primary side conversion circuit 4A is connected to the first power conversion circuit 2 and the first DC capacitor 3 via the pair of first DC bus lines 31, and the AC side terminal.
  • one end of the primary winding of the insulating transformer 49 is connected to the connection point between the switching elements 41 and 42 connected in series, and the connection point between the switching element 43 and switching element 44 connected in series is connected.
  • the other end of the primary winding of the insulating transformer 49 is connected.
  • the secondary side conversion circuit 4B of the isolation transformer 49 includes switching elements 45 to 48.
  • the switching elements 45 to 48 are connected in a full bridge type.
  • the DC side terminal of the secondary side conversion circuit 4B is connected to the second DC capacitor 5 and the third power conversion circuit 6 via the pair of second DC bus lines 51, and the AC side terminal. Is connected to the secondary winding of the insulating transformer 49.
  • one end of the secondary winding of the insulating transformer 49 is connected to the connection point between the switching elements 45 and 46 connected in series, and the connection point between the switching elements 47 and 48 connected in series is connected.
  • the other end of the secondary winding of the insulating transformer 49 is connected.
  • the second power conversion circuit 4 may include a reactor, a capacitor, etc. connected in series or in parallel with the primary winding or the secondary winding of the insulating transformer 49.
  • a reactor and a capacitor By using a reactor and a capacitor, low-loss soft switching operation becomes possible.
  • a separately prepared reactor may be externally attached to the insulating transformer 49, and the leakage inductance or the exciting inductance of the insulating transformer 49 may be used as a reactor for reducing loss.
  • the secondary side conversion circuit 4B may be configured by a diode rectifier circuit using a diode or a voltage doubler rectifier circuit using a capacitor.
  • the third power conversion circuit 6 (DC/DC converter 60) shown in FIGS. 2 and 3 includes switching elements 61 and 62, a smoothing DC reactor 63, and a smoothing capacitor 64.
  • the third power conversion circuit 6 has a circuit configuration of a step-down chopper.
  • the resistive load 71 is connected to the output terminal of the third power conversion circuit 6.
  • the voltage source load 72 is connected to the output terminal of the third power conversion circuit 6.
  • the third power conversion circuit 6 shown in FIGS. 2 and 3 has a step-down chopper circuit configuration, it may have a step-up or step-up/step-down circuit configuration, and also has an interleave configuration or parallel connection. It goes without saying that it may have a configuration.
  • IGBTs Insulated Gate Bipolar
  • Transistor Metal Oxide Semiconductor Field Effect Transistor
  • SiC Silicon Carbide
  • MOSFET Metal Oxide Semiconductor Field Effect Transistor
  • GaN GaN Nitride Emitter
  • FET Field Effect Transistor
  • FET GaN (Galium Nitride Emitter)
  • the power conversion device 100 further includes current detectors D1 and D2 and voltage detectors D3 to D6.
  • the current detector D1 detects an AC input current iac flowing from the AC power supply 11 to the first power conversion circuit 2.
  • the current detector D2 detects the DC output current Iout flowing from the third power conversion circuit 6 to the load 7.
  • the voltage detector D3 detects the AC input voltage vac applied to the first power conversion circuit 2 from the AC power supply 11.
  • the voltage detector D4 detects the voltage Vlink of the first DC capacitor 3.
  • the voltage detector D5 detects the voltage Vint of the second DC capacitor 5.
  • the voltage detector D6 detects the voltage of the smoothing capacitor 64 of the third power conversion circuit 6 as the DC output voltage Vout given to the load 7 from the third power conversion circuit 6.
  • the detectors D1 to D6 provide the detection result to the control unit 8.
  • the control unit 8 performs feedback calculation based on a part or all of the given detection value to control ON/OFF of each switching element.
  • the control unit 8 controls the first to third power converters so that the first to third power converter circuits 2, 4 and 6 start the operation stepwise as an initial operation. Control the circuits 2, 4, and 6. After all the first to third power conversion circuits 2, 4 and 6 start operating, the control unit 8 controls the first to third power conversion circuits 2, 4 and 6 so as to perform steady operation.
  • the start of the operation means that the switching operation (ON/OFF operation) of at least one switching element included in the corresponding circuit is started.
  • the fact that the first to third power conversion circuits 2, 4 and 6 start operating stepwise means that at least two power conversion circuits start operating at different times.
  • the control unit 8 calculates various output values based on the detection results of the detectors D1 to D6, and controls the first to third power conversion circuits 2, 4, 6 based on the output values.
  • the AC input current iac is controlled so as to follow a predetermined target sine wave current iac*
  • the voltage Vlink of the first DC capacitor 3 follows the predetermined target DC voltage Vlink*
  • the voltage Vint of the second DC capacitor 5 is controlled so as to follow the predetermined target DC voltage Vint*.
  • the resistance load 71 is applied as the load 7
  • the DC output voltage Vout is controlled so as to follow a predetermined target DC output voltage Vout*
  • the voltage source load 72 is applied as the load 7.
  • the DC output current Iout is controlled so as to follow the predetermined target DC output current Iout*.
  • control unit 8 calculates the current difference between the sinusoidal current command (target sine wave current) iac* synchronized with the detected value of the AC voltage vac and the detected value of the AC input current iac.
  • the control unit 8 calculates the output value by proportional control or proportional integral control with the calculated current difference as the feedback amount.
  • the control unit 8 also calculates the voltage difference between the target DC voltage Vlink* and the detected value of the DC voltage Vlink of the first DC capacitor 3, and outputs the calculated voltage difference as a feedback amount by proportional control or proportional-integral control. Calculate the value.
  • the control unit 8 also calculates the voltage difference between the target DC voltage Vint* and the detected value of the DC voltage Vint of the second DC capacitor 5, and outputs the calculated voltage difference as a feedback amount by proportional control or proportional-integral control. Calculate the value.
  • the control unit 8 calculates the voltage difference between the target DC output voltage Vout* and the detected value of the DC output voltage Vout, and uses the calculated voltage difference as the feedback amount.
  • Output value is calculated by proportional control or proportional integral control.
  • the control unit 8 calculates the voltage difference between the target DC output current Iout* and the detected value of the DC output current Iout, and calculates the calculated voltage difference as the feedback amount.
  • the output value is calculated by proportional control or proportional integral control.
  • the control unit 8 determines that the AC input current iac, the voltages Vlink and Vint of the first and second DC capacitors 3 and 5 and the DC output voltage Vout (or the DC output current Iout) are the target values.
  • the first to third power conversion circuits 2, 4 and 6 are controlled so as to follow.
  • FIG. 4 is a diagram for explaining the initial operation of the power conversion device 100 when the resistive load 71 is used as the load 7.
  • FIG. 4 shows detected values of the voltage Vlink of the first DC capacitor 3, the AC input voltage vac, the AC input current iac, the voltage Vint of the second DC capacitor 5, and the DC output voltage Vout.
  • the horizontal axis represents time, and the vertical axis represents current or voltage.
  • “1st” shown in the lower stage represents the operation start time of the first power conversion circuit 2
  • "2nd” represents the operation start time of the second power conversion circuit 4
  • “3rd” represents the operation start time.
  • 3 represents the operation start time of the power conversion circuit 6 of No. 3.
  • the time when the power conversion device 100 is in the non-operating state is defined as the initial time t0. That is, at time t0, the switching operations of the first power conversion circuit 2, the second power conversion circuit 4, and the third power conversion circuit 6 are all stopped. At time t0, the voltage Vlink of the first DC capacitor 3 and the voltage Vint of the second DC capacitor 5 are 0, respectively.
  • the controller 8 controls the voltage Vlink of the first DC capacitor 3, the voltage Vint of the second DC capacitor 5, and the DC output voltage Vout to change as follows based on the detection results of the detectors D1 to D6. , And controls the first to third power conversion circuits 2, 4, and 6.
  • the AC input voltage vac is applied to the input terminal of the first power conversion circuit 2.
  • the first DC capacitor 3 is passively charged via the built-in diode of each switching element of the first power conversion circuit 2 or the external diode.
  • the voltage Vlink of the first DC capacitor 3 rises to the initial charging voltage Vlink0.
  • the initial charging voltage Vlink0 satisfies the equation (1) with respect to the effective values Vac and rms of the AC input voltage vac. Note that “ ⁇ 2Vac,rms” in the equation (1) corresponds to the maximum value of the AC input voltage vac.
  • the switching operation of the first power conversion circuit 2 is started.
  • the effective duty ratio of the first power conversion circuit 2 is gradually increased, so that the voltage Vlink of the first DC capacitor 3 is gradually increased. Thereby, abrupt voltage change is prevented.
  • the switching operations of the second power conversion circuit 4 and the third power conversion circuit 6 are stopped.
  • the voltage Vlink of the first DC capacitor 3 reaches the predetermined first threshold voltage Vlink,th.
  • the power factor control of the AC input current iac by the first power conversion circuit 2 is started, and the switching operation of the second power conversion circuit 4 is started.
  • the first threshold voltage Vlink,th satisfies the condition of Expression (2).
  • the first power conversion circuit 2 continues the normal operation (boosting operation). Can't do it. Specifically, the current path between the AC power supply 11 and the first DC capacitor 3 is fixed regardless of whether the switching elements 21 to 24 are turned on or off. Therefore, the voltage Vlink of the first DC capacitor 3 needs to be maintained at or above the maximum value of the AC input voltage vac.
  • the initial charging voltage Vlink0 of the first DC capacitor 3 is equal to or higher than the maximum value ( ⁇ 2Vac, rms) of the AC input voltage vac, and before the operation of the second power conversion circuit 4 starts, The voltage Vlink of the DC capacitor 3 is maintained above the AC input voltage vac. However, when the operation of the second power conversion circuit 4 is started, a current flows from the first DC capacitor 3 to the second DC capacitor 5, so that the voltage Vlink of the first DC capacitor 3 decreases, and The voltage Vlink of the DC capacitor 3 of No. 1 may be lower than the maximum value of the AC input voltage vac.
  • the switching operation of the second power conversion circuit 4 is performed after the voltage Vlink of the first DC capacitor 3 is raised to the first threshold voltage Vlink,th by the first power conversion circuit 2. Be started.
  • the switching operation of the second power conversion circuit 4 can be started in a state where a certain margin is secured between the voltage Vlink of the first DC capacitor 3 and the AC input voltage vac.
  • the effective duty ratio of the second power conversion circuit 4 is gradually increased from 0, and the current flowing from the first DC capacitor 3 to the second DC capacitor 5 is gradually increased from 0. ..
  • a sharp decrease in the voltage Vlink of the first DC capacitor 3 due to the start of the operation of the second power conversion circuit 4 is suppressed.
  • the duty ratio gradually increases is not limited to the case where the duty ratio linearly and continuously increases at a constant rate of change as in the example of Fig. 4, and the duty ratio is curvilinear and continuous. And the case where the duty ratio increases stepwise through a plurality of steps. However, when the duty ratio is increased stepwise, it is preferable that the number of steps is set sufficiently large and the change width in one step is as small as possible.
  • the voltage Vlink of the first DC capacitor 3 is prevented from becoming lower than the maximum value of the AC input voltage vac, and the first power conversion circuit 2 can stably continue normal operation.
  • the first threshold voltage Vlink,th is set to a value smaller than the target DC voltage Vlink*, the voltage Vlink of the first DC capacitor 3 is prevented from becoming an overvoltage, and the second power is reduced. The time until the operation of the conversion circuit 4 starts can be shortened.
  • the switching operation of the second power conversion circuit 4 is started, and at the same time, the power factor control by the first power conversion circuit 2 is started.
  • the magnitude (amplitude) of the AC input current iac can be gradually increased from 0 to the maximum value. Therefore, the first and second DC capacitors 3 and 5 can be stably charged.
  • the voltage Vlink of the first DC capacitor 3 reaches the target DC voltage Vlink*
  • the voltage Vlink is controlled so as to follow the target DC voltage Vlink*. Control is performed such that the voltage Vlink of the first DC capacitor 3 reaches the first threshold voltage Vlink,th at time t3, and the voltage Vlink of the first DC capacitor 3 follows the target DC voltage Vlink*. May be done.
  • the second threshold voltage Vint,th satisfies the condition of Expression (3).
  • the third power conversion circuit 6 when the voltage Vint of the second DC capacitor 5 becomes lower than the DC output voltage Vout output to the resistive load 71 during the operation of the third power conversion circuit 6, the third power conversion circuit 6 operates normally. It becomes impossible to continue the operation (step-down operation). Specifically, by setting the duty ratio of the third power conversion circuit 6 to 0, the switching element 61 is constantly turned off, and power cannot be supplied to the resistive load 71. Therefore, the voltage Vint of the second DC capacitor 5 needs to be maintained higher than the DC output voltage Vout.
  • the operation of the third power conversion circuit 6 is started after the voltage Vint of the second DC capacitor 5 is raised to the second threshold voltage Vint,th by the second power conversion circuit 4. ..
  • the switching operation of the third power conversion circuit 6 can be started with a certain margin secured between the voltage Vint of the second DC capacitor 5 and the DC output voltage Vout.
  • the effective duty ratio of the third power conversion circuit 6 is gradually increased from 0, and the current flowing from the second DC capacitor 5 to the resistive load 71 is gradually increased from 0.
  • a sharp drop in the voltage Vint of the second DC capacitor 5 due to the start of the operation of the third power conversion circuit 6 is suppressed.
  • the voltage Vint of the second DC capacitor 5 is prevented from becoming lower than the DC output voltage Vout, and the third power conversion circuit 6 can stably continue normal operation.
  • the voltage Vint of the second DC capacitor 5 is controlled so as to follow the target DC voltage Vint*. Control is performed such that the voltage Vint of the second DC capacitor 5 follows the target DC voltage Vint* from the time when the voltage Vint of the second DC capacitor 5 reaches the second threshold voltage Vint,th at time t4. May be done.
  • FIG. 4 shows only the change in the DC output voltage Vout as the change in the power supplied to the resistive load 71
  • the DC output current Iout also increases as the DC output voltage Vout increases.
  • the on/off control of the switching element is performed using the detected value of the DC output voltage Vout instead of the detected value of the DC output current Iout. Illustration of the DC output current Iout is omitted.
  • the operations of the first to third power conversion circuits 2, 4, and 6 are sequentially started, so that the first and second power conversion circuits are started.
  • the DC capacitors 3 and 5 are sequentially charged.
  • the overcurrent in the first to third power conversion circuits 2, 4, and 6 The power supply to the load 7 can be stably started without generating the overvoltage of the second DC capacitors 3 and 5.
  • the voltage is applied to the first and second DC capacitors 3 and 5 and the load 7 at the same time.
  • the current flows in.
  • an overcurrent may occur in the first to third power conversion circuits 2, 4, 6 and the first and second DC capacitors 3, 5 may become overvoltage.
  • the voltages of the first and second DC capacitors 3 and 5 can be individually controlled. .. Specifically, the voltage Vlink of the first DC capacitor 3 can be controlled by adjusting the duty ratio of the first power conversion circuit 2 while the operation of the second power conversion circuit 4 is stopped. it can. Further, the voltage Vint of the second DC capacitor 5 can be controlled by adjusting the duty ratio of the second power conversion circuit 4 while the operation of the third power conversion circuit 6 is stopped. Therefore, the voltage of the first and second DC capacitors 3 and 5 can be stably increased.
  • the rate of change (gradient) of the voltage Vlink is different, the rate of change of the voltage Vlink may be constant from the voltage Vlink of 0 to the target DC voltage Vlink*.
  • the voltage Vint is divided into a period from the voltage Vint reaching 0 to the second threshold voltage Vint,th and a period from the voltage Vint reaching the second threshold voltage Vint,th to the target DC voltage Vint*.
  • the rate of change of the voltage Vint may be constant from the voltage Vint of 0 to the target DC voltage Vint*.
  • the voltage Vlink and the voltage Vint may not change continuously, but may change stepwise through a plurality of steps. However, in order to effectively prevent the occurrence of overcurrent and overvoltage, it is preferable that the number of steps is set sufficiently large and the voltage change width in one step is as small as possible.
  • FIG. 5 is a diagram for explaining a first example of the initial operation of the power conversion device 100 when the voltage source load 72 is applied to the load 7. Similar to the example of FIG. 4, FIG. 5 shows the detected values of the voltages Vlink, vac, Vint, Vout and the current iac, as well as the detected values of the DC output current Iout. As described above, when the voltage source load 72 is used as the load 7, the on/off control of the switching element is performed using the detected value of the DC output current Iout.
  • the voltage source load 72 generates a constant DC voltage. Therefore, at time t0 when the power conversion device 100 is in the non-operating state, the DC voltage from the voltage source load 72 is applied to the output terminal of the third power conversion circuit 6. This voltage is detected as the voltage Vout. In this case, the second DC capacitor 5 is passively charged through the built-in diode of the switching element of the third power conversion circuit 6 or the external diode. As a result, the voltage Vint of the second DC capacitor 5 is maintained at the initial charging voltage Vint0.
  • the AC input voltage vac is applied to the input terminal of the first power conversion circuit 2 at time t1.
  • the voltage Vlink of the first DC capacitor 3 rises to the initial charging voltage Vlink0.
  • the switching operation of the first power conversion circuit 2 is started.
  • the effective duty ratio of the first power conversion circuit 2 is gradually increased, so that the voltage Vlink of the first DC capacitor 3 is gradually increased.
  • the first DC capacitor 3 The switching operation of the second power conversion circuit 4 may be started before the voltage Vlink reaches the first threshold voltage Vlink,th.
  • the third power is added to the first power conversion circuit 2 and the second power conversion circuit 4.
  • the switching operation of the conversion circuit 6 is started, and power is supplied from the third power conversion circuit 6 to the resistance load 71.
  • the effective duty ratio of the third power conversion circuit 6 is gradually increased from 0, so that the DC current Iout given to the voltage source load 72 is gradually increased from 0. That is, the electric power applied to the voltage source load 72 gradually increases from zero.
  • the first to third power conversion circuits 2, 4, and 6 are started in order, so that the first and the second power conversion circuits are started.
  • the voltages Vlink and Vint of the two DC capacitors 3 and 5 can be individually and accurately controlled.
  • the power converter 100 transfers the load 7 to the load 7 without generating an overcurrent in the first to third power conversion circuits 2, 4 and 6 and an overvoltage in the first and second DC capacitors 3 and 5.
  • the power supply can be stably started.
  • the operation start timing of the second power conversion circuit 4 and the operation start timing of the third power conversion circuit 6 can be set relatively flexibly. it can. A specific example will be described below.
  • FIG. 6 is a diagram for explaining a second example of the initial operation of the power conversion device 100 when the voltage source load 72 is applied to the load 7.
  • the example of FIG. 6 will be described focusing on the points different from the example of FIG.
  • the operation of the second power conversion circuit 4 has not started, so no current flows between the first DC capacitor 3 and the second DC capacitor 5. Therefore, the operation of the first power conversion circuit 2 does not affect the voltage Vint of the second DC capacitor 5, and the operation of the third power conversion circuit 6 does not affect the voltage Vlink of the first DC capacitor 3. .. Therefore, by individually adjusting the duty ratios of the first and third power conversion circuits 2 and 6, the voltages Vlink and Vint of the first and second DC capacitors 3 can be individually controlled.
  • the time when the operation of the third power conversion circuit 6 is started may coincide with the time when the voltage Vlink of the first DC capacitor 3 reaches the first threshold voltage Vlink,th. It may be before the voltage Vlink of the DC capacitor 3 reaches the first threshold voltage Vlink,th.
  • the voltage Vint of the second DC capacitor 5 reaches the second threshold voltage Vint,th.
  • the power factor control by the first power conversion circuit 2 is started, and the switching operation of the second power conversion circuit 4 is started.
  • current flows from the power conversion device 100 to the voltage source load 72, and power is supplied to the voltage source load 72.
  • the effective duty ratio of the second power conversion circuit 4 is gradually increased from 0, so that the DC current Iout given to the voltage source load 72 is gradually increased from 0.
  • the second DC capacitor 5 can be charged with the electric power from the voltage source load 72. If the operation of the second power conversion circuit 4 is not started, the operation of the first power conversion circuit 2 and the operation of the third power conversion circuit 6 do not affect each other. Therefore, as in the example of FIG. 6, the operation of the third power conversion circuit 6 is started after the first power conversion circuit 2, and the operation of the third power conversion circuit 6 is followed by the second power conversion circuit 4. The operation of can be started.
  • FIG. 7 is a diagram for explaining a third example of the initial operation of the power conversion device 100 when the voltage source load 72 is applied to the load 7.
  • the example of FIG. 7 will be described focusing on the points different from the example of FIG.
  • the voltage source load 72 is not electrically connected to the output terminal of the third power conversion circuit 6 at time t0. Therefore, at time t0, no voltage is applied from the voltage source load 72 to the output terminal of the third power conversion circuit 6, and the voltage Vint of the second DC capacitor 5 is zero.
  • the voltage source load 72 is electrically connected to the output terminal of the third power conversion circuit 6 at time t2c. Connected. As a result, the voltage of the voltage source load 72 is applied to the output terminal of the third power conversion circuit 6 and detected as the voltage Vout.
  • the second DC capacitor 5 is passively charged via the built-in diode of the switching element of the third power conversion circuit 6 or the external diode, and at time t3c, the second DC capacitor 5 is charged.
  • the voltage Vint reaches the initial charging voltage Vint0.
  • time t1 even if the AC input voltage vac is applied to the input terminal of the first power conversion circuit 2 and the voltage of the voltage source load 72 is applied to the output terminal of the third power conversion circuit 6 at the same time. Good.
  • the switching operation of the third power conversion circuit 6 is started.
  • the effective duty ratio of the third power conversion circuit 6 is gradually increased, so that the voltage Vint of the second DC capacitor 5 is gradually increased.
  • the voltage Vint of the second DC capacitor 5 reaches the second threshold voltage Vint,th.
  • the switching operation of the first power conversion circuit 2 is started.
  • the effective duty ratio of the first power conversion circuit 2 is gradually increased, so that the voltage Vlink of the first DC capacitor 3 is gradually increased.
  • the power factor control of the first power conversion circuit 2 is started and the second power conversion circuit is started.
  • the switching operation of No. 4 is started.
  • the effective duty ratio of the second power conversion circuit 4 is gradually increased from 0, so that the DC current Iout given to the voltage source load 72 is gradually increased from 0.
  • the second DC capacitor 5 can be charged by the electric power from the voltage source load 72. Further, in a state where the operation of the second power conversion circuit 4 is not started, the operation of the first power conversion circuit 2 and the operation of the third power conversion circuit 6 do not influence each other. Therefore, as in the example of FIG. 7, the operation of the third power conversion circuit 6 is started after the first power conversion circuit 2, and the operation of the second power conversion circuit 4 is started after the third power conversion circuit 6. The operation of can be started.
  • the first power conversion circuit 2 and the third power conversion circuit 6 start operating at different times, but the first power conversion circuit 2 and the third power conversion circuit The circuit 6 and the circuit 6 may start operating at the same time.
  • the operations of the first to third power conversion circuits 2, 4, and 6 are started stepwise, so that the first to third power conversion circuits are started.
  • the voltages of the first and second DC capacitors 3, 5 can be individually controlled. Thereby, the voltage of the first and second DC capacitors 3 can be stably increased.
  • the first power conversion circuit 2 is composed only of the AC/DC converter 20
  • the third power conversion circuit 6 is composed only of the DC/DC converter 60.
  • the configurations of the power conversion circuits 2 and 6 are not limited to this.
  • FIG. 8: is a figure which shows the modification of the power converter device 100 which concerns on Embodiment 1. As shown in FIG.
  • the power conversion device 100 shown in FIG. 8 includes a first power conversion circuit 2A in place of the first power conversion circuit 2 and a third power conversion circuit 6A in place of the third power conversion circuit 6.
  • the first power conversion circuit 2A includes a step-down DC/DC converter 200 in addition to the AC/DC converter 20 of FIGS. 2 and 3.
  • DC/DC converter 200 includes a capacitor 211, switching elements 212 and 213, and a reactor 214.
  • the AC/DC converter 20 converts an AC voltage into a DC voltage, and the converted DC voltage is stepped down by the DC/DC converter and output.
  • the power factor control is performed by the boost converter (AC/DC converter 20 in this example) in order to suppress harmonic distortion.
  • the boost converter AC/DC converter 20 in this example
  • the DC/DC converter 200 can reduce the voltage applied to the insulating transformer 49, and can suppress an increase in iron loss.
  • the third power conversion circuit 6A shown in FIG. 8 includes an insulation type DC/DC converter 600 in addition to the DC/DC converter 60 of FIGS. 2 and 3.
  • the insulation type DC/DC converter 600 includes an insulation transformer 610, switching elements 611 to 618, and a capacitor 619.
  • the DC voltage is converted into the DC voltage by the DC/DC converter 60, and the converted DC voltage is transformed by the insulating DC/DC converter 60 and output.
  • the switching elements 212 and 213 of the DC/DC converter 200 and the switching elements 611 to 618 of the insulation type DC/DC converter 600 are on/off controlled by the control unit 8.
  • the operation of the AC/DC converter 20 and the operation of the DC/DC converter 200 may be started at the same time, and the operation of the DC/DC converter 200 may be started after a lapse of time after the operation of the AC/DC converter 20 is started.
  • the operation may be started.
  • the operation of the DC/DC converter 60 and the operation of the insulation type DC/DC converter 600 may be started simultaneously, and the insulation type DC/DC may be started after a lapse of time from the start of the operation of the DC/DC converter 60.
  • the operation of converter 600 may be started.
  • the voltage source load 72 is used as the load 7
  • the operation of the DC/DC converter 60 may be started after a lapse of time after the operation of the insulating DC/DC converter 600 is started.
  • the power conversion device 100 may further include other power conversion circuits in addition to the first to third power conversion circuits 2 (2A), 4, 6 (6A).
  • FIG. 9: is a figure which shows the other modification of the power converter device 100 which concerns on Embodiment 1. As shown in FIG. In the power conversion device 100 shown in FIG. 9, the fourth power conversion circuit 91 and the fifth power conversion circuit are arranged in parallel with the first power conversion circuit 2, the first DC capacitor 3, and the second power conversion circuit 4. The circuit 92 is connected.
  • the fourth power conversion circuit 91 includes switching elements 911 to 914, a capacitor 915, and a non-contact power receiving coil 916.
  • the switching elements 911 to 914 are connected in a full bridge type.
  • One end of the non-contact power receiving coil 916 is connected to a connection point where the switching element 911 and the switching element 912 are connected in series, and non-contact power reception is performed at a connection point where the switching element 913 and the switching element 914 are connected in series.
  • the other end of the coil 916 is connected.
  • the fourth power conversion circuit 91 is connected to the pair of second DC buses 51 via the pair of third DC buses 917, respectively.
  • the fifth power conversion circuit 92 includes switching elements 921 to 928, a DC link capacitor 929, AC reactors 931 and 932, and a non-contact power transmission coil 933.
  • the switching elements 921 to 924 and the switching elements 925 to 928 are connected in a full bridge type.
  • One ends of the AC reactors 931 and 932 are connected to the AC power supply 11.
  • the other end of AC reactor 931 is connected to a connection point between switching element 921 and switching element 922 that are connected in series, and the other end of AC reactor 932 is a connection point between switching element 923 and switching element 924 that are connected in series. It is connected to the.
  • the DC link capacitor 929 is connected to the positive and negative electrodes of the DC bus connecting the switching elements 921 to 924 and the switching elements 925 to 928.
  • One end of the non-contact power transmission coil 933 is connected to a connection point between the switching element 925 and the switching element 926 connected in series, and the non-contact power transmission coil 933 is connected to a connection point between the switching element 927 and the switching element 928 connected in series. The ends are connected.
  • the non-contact power reception coil 916 of the fourth power conversion circuit 91 and the non-contact power transmission coil 933 of the fifth power conversion circuit 92 are magnetically coupled to each other, so that the fifth power conversion circuit 92 outputs the fourth power. Electric power is transmitted to the conversion circuit 91 in a contactless manner. A DC voltage is applied from the fourth power conversion circuit 91 to the second DC capacitor 5 via the third DC bus 917.
  • a power conversion device according to Embodiment 2 of the present invention will be described focusing on differences from the power conversion device 100 according to Embodiment 1 above.
  • the configuration of the power conversion device according to the second embodiment is substantially the same as the case shown in the first embodiment, and therefore detailed description of the configuration will not be repeated.
  • FIG. 10 is a diagram showing a specific circuit configuration example of the power conversion device 100 according to the second embodiment.
  • the power conversion device 100 according to the second embodiment includes a first power conversion circuit 2B in place of the first power conversion circuit 2 and a third power conversion circuit 6B in place of the third power conversion circuit 6.
  • the first power conversion circuit 2B includes a DC/DC converter 20B including switching elements 221, 222 and a smoothing DC reactor 223.
  • the DC/DC converter 20B has a circuit configuration of a step-down chopper.
  • the DC power supply 12 as the input power supply 1 is connected to the input terminal of the first power conversion circuit 2B.
  • the DC/DC converter 20B shown in FIG. 10 has a step-down chopper circuit configuration, it may have a step-up type or step-up/down type circuit configuration, and also has an interleave configuration or a parallel connection configuration. It goes without saying that it is good.
  • the third power conversion circuit 6B includes switching elements 621 to 624 and AC reactors 625 and 626, and includes an inverter 60B that converts a DC voltage into an AC voltage.
  • the switching elements 621 to 624 are connected in a full bridge type.
  • One end of the AC reactor 625 is connected to a connection point between the switching element 621 and the switching element 622.
  • One end of the AC reactor 626 is connected to a connection point between the switching element 623 and the switching element 624.
  • a resistive load 71 is connected as the load 7 to the other ends of the AC reactors 625 and 626.
  • the AC reactors 625 and 626 are connected to both sides of the AC power supply, but may be connected to only one side. That is, only one of AC reactors 625 and 626 may be used.
  • the DC/DC converter 20B of the first power conversion circuit 2B shown in FIG. 10 has a configuration in which the input/output is opposite to that of the DC/DC converter 60 of the third power conversion circuit 6 shown in FIGS. 2 and 3.
  • the inverter 60B of the third power conversion circuit 6B shown in FIG. 10 has a configuration in which the input and output are opposite to those of the AC/DC converter 20 of the first power conversion circuit 2 shown in FIGS. 2 and 3. Therefore, when the power transmission direction in the first embodiment is defined as the forward direction and the opposite direction is defined as the reverse direction, the power conversion device 100 according to the second embodiment transmits the power in the reverse direction.
  • the power conversion device 100 is configured to be capable of bidirectionally transmitting power, it is possible to realize both the first embodiment and the second embodiment by the common power conversion device 100.
  • the current detector D1 detects the DC input current Idc flowing from the DC power supply 12 to the first power conversion circuit 2B.
  • the current detector D2 detects the AC output current iout flowing from the third power conversion circuit 6B to the resistance load 71.
  • the voltage detector D3 detects the DC input voltage Vdc supplied from the DC power supply 12 to the first power conversion circuit 2.
  • the voltage detector D4 detects the voltage Vint of the first DC capacitor 3.
  • the voltage detector D5 detects the voltage Vlink of the second DC capacitor 5.
  • the voltage detector D6 detects the AC output voltage vout given to the resistive load 71 from the third power conversion circuit 6.
  • the control unit 8 performs feedback calculation based on a part or all of the detection values given from the detectors D1 to D6, and controls on/off of each switching element.
  • the control unit 8 calculates a voltage difference between a predetermined target DC voltage Vint* and a detected value of the DC voltage Vint of the first DC capacitor 3, and uses the calculated voltage difference as a feedback amount for proportional control or proportional-integral control.
  • the output value is calculated by.
  • control unit 8 calculates a voltage difference between a predetermined target DC voltage Vlink* and a detected value of the DC voltage Vlink of the second DC capacitor 5, and performs proportional control or proportional control using the calculated voltage difference as a feedback amount. Output value is calculated by integral control.
  • control unit 8 sets a target obtained by multiplying the effective value Vout, rms* of the target AC output voltage, which is predetermined so that the output voltage to the resistive load 71 is a sine wave AC, by the sine wave voltage having an amplitude of ⁇ 2.
  • the voltage difference between the AC output voltage vout* and the AC output voltage vout is calculated, and the calculated voltage difference is used as a feedback amount to calculate the output by proportional control or proportional integral control.
  • the voltage Vint of the first DC capacitor 3 is controlled so as to follow the target DC voltage Vint*, and the voltage Vlink of the second DC capacitor 5 follows the target DC voltage Vlink*. It is controlled so that the AC output voltage vout follows the target AC output voltage vout*.
  • FIG. 11 is a diagram for explaining the initial operation in the second embodiment.
  • FIG. 11 shows the detected values of the DC input voltage Vdc, the voltage Vint of the first DC capacitor 3, the voltage Vlink of the second DC capacitor 5, and the AC output voltage vout.
  • the control unit 8 controls the voltage Vint of the first DC capacitor 3, the voltage Vlink of the second DC capacitor 5, and the AC output voltage vout to change as follows based on the detection results of the detectors D1 to D6. , And controls the first to third power conversion circuits 2B, 4, 6B.
  • the DC input voltage Vdc is applied to the input terminal of the first power conversion circuit 2B.
  • the first DC capacitor 3 is passively charged via the built-in diode or the external diode of each switching element of the first power conversion circuit 2B.
  • the voltage Vint of the first DC capacitor 3 rises to the initial charging voltage Vint0. It should be noted that time t1d and time t2d may substantially coincide with each other by instantaneously charging the voltage Vint of the first DC capacitor 3.
  • the switching operation of the first power conversion circuit 2B is started.
  • the effective duty ratio of the first power conversion circuit 2B is gradually increased, so that the voltage Vint of the first DC capacitor 3 is gradually increased.
  • the voltage Vint of the first DC capacitor 3 reaches the predetermined first threshold voltage Vint,th.
  • the switching operation of the second power conversion circuit 4 is started.
  • the first threshold voltage Vint,th satisfies the condition of Expression (4).
  • the first power conversion circuit 2B continues the normal operation (boosting operation). Can't do it. Specifically, the current path between the DC power supply 12 and the first DC capacitor 3 is fixed regardless of whether the switching elements 21 to 24 are turned on or off. Therefore, the voltage Vint of the first DC capacitor 3 needs to be maintained higher than the DC input voltage Vdc.
  • the switching operation of the second power conversion circuit 4 is started after the voltage Vint of the first DC capacitor 3 is raised to the first threshold voltage Vint,th by the first power conversion circuit 2B. It As a result, the switching operation of the second power conversion circuit 4 can be started in a state in which a certain margin is provided between the voltage Vint of the first DC capacitor 3 and the DC input voltage Vdc. Further, in the present embodiment, the effective duty ratio of the second power conversion circuit 4 is gradually increased from 0, and the current flowing from the first DC capacitor 3 to the second DC capacitor 5 is gradually increased from 0. .. As a result, a sharp drop in the voltage Vint of the first DC capacitor 3 due to the start of operation of the second power conversion circuit 4 is suppressed.
  • the voltage Vint of the first DC capacitor 3 is prevented from becoming lower than the DC input voltage Vdc, and the first power conversion circuit 2 can stably continue normal operation.
  • the first threshold voltage Vint,th is set to a value smaller than the target DC voltage Vint*, the voltage Vint of the first DC capacitor 3 is prevented from becoming an overvoltage, and the second power The time until the operation of the conversion circuit 4 starts can be shortened.
  • the voltage Vint of the first DC capacitor is controlled so as to follow the target DC voltage Vint*.
  • the second threshold voltage Vlink,th satisfies the condition of Expression (5). Note that “ ⁇ 2Vout*,rms” in the equation (5) corresponds to the maximum value of the target AC output voltage vout*.
  • the voltage Vlink of the second DC capacitor is controlled so as to follow the target DC voltage Vlink*.
  • the operations of the first to third power conversion circuits 2B, 4, 6B are started stepwise, whereby the first to third power conversion circuits 2B, 4, 4 are started.
  • the voltages of the first and second DC capacitors 3 and 5 can be individually controlled. Thereby, the voltage of the first and second DC capacitors 3 and 5 can be stably increased.
  • the voltage source load 72 may be used as the load 7, and similarly to the example of FIG. 8, the first power conversion circuit 2B and the third power conversion circuit 6B may be different from each other.
  • a circuit may be added, and as in the example of FIG. 9, another power conversion circuit may be connected to the first to third power conversion circuits 2B, 4, 6B.
  • FIG. 12 is a diagram illustrating an example in which at least a part of the functions of the control unit 8 is realized by software.
  • the control unit 8 includes a processing device (processor) 501 and a storage device (memory) 502.
  • the processing device 501 is, for example, a CPU (central processing unit), and realizes at least a part of the functions of the control unit 8 in the above-described embodiment by reading and executing a program stored in the storage device 502. You can

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Abstract

A first power conversion circuit converts a voltage from an input power supply into a DC voltage and outputs the DC voltage after the conversion. A second power conversion circuit is connected to the first power conversion circuit via a first DC bus line, transforms the DC voltage output from the first power conversion circuit, and outputs a DC voltage after the transformation. A third power conversion circuit is connected to the second power conversion circuit via a second DC bus line, converts the DC voltage output from the second power conversion circuit, and outputs a DC voltage after the conversion to a load. A first DC capacitor is connected to the first DC bus line, and a second DC capacitor is connected to the second DC bus line. A control unit controls the first, second, and third power conversion circuits so that power is output from the third power conversion circuit to the load after the first, second, and third power conversion circuits have started operation in stages, the voltage of the first DC capacitor has reached a first threshold voltage, and the voltage of the second DC capacitor has reached a second threshold voltage.

Description

電力変換装置Power converter
　この発明は、少なくとも３つの電力変換回路を有する電力変換装置に関する。 The present invention relates to a power conversion device having at least three power conversion circuits.
　従来、交流電源から供給された電力を絶縁しつつ直流電力に変換して負荷に供給する電力変換装置が用いられる。このような電力変換装置は、一般的に、交流電力を直流電力に変換する電力変換回路（ＡＣ／ＤＣコンバータ）と、その直流電力を絶縁トランスを用いて所望の大きさの直流電力に変換して出力する電力変換回路（絶縁型ＤＣ／ＤＣコンバータ）とを備える。また、直流電源から供給された電力を任意の直流電力に変換する電力変換装置においても、絶縁を必要とする場合であってかつ入出力電圧範囲を広く設定する場合には、直流電源からの供給電力をある一定の直流電力に変換する電力変換回路（ＤＣ／ＤＣコンバータ）と、絶縁型ＤＣ／ＤＣコンバータとの２つの電力変換回路により電力変換装置が構成される場合がある。 Conventionally, a power converter is used that insulates the power supplied from the AC power supply, converts it to DC power, and supplies it to the load. Such a power converter is generally a power conversion circuit (AC/DC converter) that converts AC power into DC power, and converts the DC power into DC power of a desired size using an insulating transformer. And a power conversion circuit (isolated DC/DC converter) that outputs the power. In addition, even in a power converter that converts the power supplied from the DC power supply to any DC power, if insulation is required and the input/output voltage range is set wide, the power supply from the DC power supply is used. A power conversion device may be configured by two power conversion circuits, that is, a power conversion circuit (DC/DC converter) that converts electric power into a certain DC power and an insulating DC/DC converter.
　このように２つの電力変換回路で電力変換装置を構成する場合、出力電圧を広範囲に制御すると絶縁型ＤＣ／ＤＣコンバータの損失が増加する問題がある。そこで、絶縁型コンバータの出力側に電力変換回路を追加することで、直列接続された３つの電力変換回路により電力変換装置を構成することが検討されている（例えば、特許文献１参照）。 When configuring a power conversion device with two power conversion circuits in this way, if the output voltage is controlled over a wide range, there is a problem that the loss of the insulation type DC/DC converter increases. Therefore, it is considered that a power conversion device is configured by three power conversion circuits connected in series by adding a power conversion circuit to the output side of the insulating converter (see, for example, Patent Document 1).
　特許文献１記載の電源装置は、互いに直列に接続されたＡＣ／ＤＣコンバータ、絶縁型ＤＣ／ＤＣコンバータおよび双方向ＤＣ／ＤＣコンバータを備える。ＡＣ／ＤＣコンバータは、交流電源からの交流電圧を変換して直流電圧を出力する。絶縁型ＤＣ／ＤＣコンバータは、ＡＣ／ＤＣコンバータから出力された直流電圧を変換してリンク電圧を出力する。双方向ＤＣ／ＤＣコンバータは、絶縁型ＤＣ／ＤＣコンバータから出力されたリンク電圧の値を調整し、調整後のリンク電圧をバッテリに与える。ＡＣ／ＤＣコンバータと絶縁型ＤＣ／ＤＣコンバータとの間、および絶縁型ＤＣ／ＤＣコンバータと双方向ＤＣ／ＤＣコンバータとの間には、それぞれ平滑コンデンサが接続されている。 The power supply device described in Patent Document 1 includes an AC/DC converter, an insulating DC/DC converter, and a bidirectional DC/DC converter that are connected in series. The AC/DC converter converts an AC voltage from an AC power source and outputs a DC voltage. The insulation type DC/DC converter converts the DC voltage output from the AC/DC converter and outputs a link voltage. The bidirectional DC/DC converter adjusts the value of the link voltage output from the isolated DC/DC converter, and gives the adjusted link voltage to the battery. Smoothing capacitors are respectively connected between the AC/DC converter and the isolated DC/DC converter, and between the isolated DC/DC converter and the bidirectional DC/DC converter.
特開２０１５－２０８１７１号公報JP, 2005-208171, A
　上記特許文献１の電源装置においては、ＡＣ／ＤＣコンバータ、絶縁型ＤＣ／ＤＣコンバータおよび双方向ＤＣ／ＤＣコンバータの動作が開始されると、２つの平滑コンデンサに同時に電流が流れ込む。そのため、これらの回路間で過電流が発生するといった問題がある。 In the power supply device of the above Patent Document 1, when the operations of the AC/DC converter, the insulating DC/DC converter, and the bidirectional DC/DC converter are started, current flows into the two smoothing capacitors at the same time. Therefore, there is a problem that an overcurrent is generated between these circuits.
　本発明は、上記の問題点を解決するためになされたものであり、動作開始時における過電流の発生を防止することが可能な電力変換装置を得ることを目的とする。 The present invention has been made to solve the above problems, and an object thereof is to obtain a power conversion device capable of preventing the occurrence of overcurrent at the start of operation.
　本発明に係る電力変換装置は、入力電源からの電圧を直流電圧に変換し、変換後の直流電圧を出力する第１の電力変換回路と、第１の直流母線を介して第１の電力変換回路に接続され、第１の電力変換回路から出力された直流電圧を変圧し、変圧後の直流電圧を出力する第２の電力変換回路と、第２の直流母線を介して第２の電力変換回路に接続され、第２の電力変換回路から出力された直流電圧を変換し、変換後の直流電圧を負荷に出力する第３の電力変換回路と、第１の直流母線に接続された第１の直流コンデンサと、第２の直流母線に接続された第２の直流コンデンサと、第１、第２および第３の電力変換回路が段階的に動作を開始し、第１の直流コンデンサの電圧が第１の閾値電圧に達しかつ第２の直流コンデンサの電圧が第２の閾値電圧に達した後に、第３の電力変換回路から負荷に電力が出力されるように、第１、第２および第３の電力変換回路を制御する制御部と、を備える。 A power conversion device according to the present invention converts a voltage from an input power source into a DC voltage and outputs a converted DC voltage, and a first power conversion circuit via a first DC bus. A second power conversion circuit that is connected to the circuit, transforms the DC voltage output from the first power conversion circuit, and outputs the transformed DC voltage; and second power conversion via a second DC bus bar. A third power conversion circuit connected to the circuit for converting the DC voltage output from the second power conversion circuit and outputting the converted DC voltage to the load; and a first power conversion circuit connected to the first DC bus. Of the DC capacitor, the second DC capacitor connected to the second DC bus, and the first, second, and third power conversion circuits start to operate in stages, and the voltage of the first DC capacitor becomes After the first threshold voltage is reached and the voltage of the second DC capacitor reaches the second threshold voltage, the first power conversion circuit outputs power to the load so that the first power conversion circuit outputs the power to the load. The control part which controls the power converter circuit of 3 is provided.
　本発明に係る電力変換装置によれば、第１、第２および第３の電力変換回路の動作が段階的に開始されるため、第１および第２の直流コンデンサの電圧を個別に制御することができ、過電流の発生を防止することが可能である。 According to the power conversion device of the present invention, the operations of the first, second, and third power conversion circuits are started in stages, so that the voltages of the first and second DC capacitors can be individually controlled. Therefore, it is possible to prevent the occurrence of overcurrent.
実施の形態１における電力変換装置を含む電源システムの概略構成を示す模式図である。1 is a schematic diagram showing a schematic configuration of a power supply system including a power conversion device according to a first embodiment. 実施の形態１に係る電力変換装置の具体的な回路構成例を示す図である。It is a figure which shows the specific circuit structural example of the power converter device which concerns on Embodiment 1. 実施の形態１に係る電力変換装置の具体的な回路構成例を示す図である。It is a figure which shows the specific circuit structural example of the power converter device which concerns on Embodiment 1. 実施の形態１において負荷に抵抗負荷が用いられた場合の電力変換装置の初期動作についての説明するための図である。FIG. 4 is a diagram for explaining an initial operation of the power conversion device when a resistive load is used as a load in the first embodiment. 実施の形態１において負荷に電圧源負荷が用いられた場合の電力変換装置の初期動作の第１の例について説明するための図である。FIG. 6 is a diagram for describing a first example of an initial operation of the power conversion device when a voltage source load is used as a load in the first embodiment. 実施の形態１において負荷に電圧源負荷が用いられた場合の電力変換装置の初期動作の第２の例について説明するための図である。FIG. 5 is a diagram for describing a second example of the initial operation of the power conversion device when the voltage source load is used as the load in the first embodiment. 実施の形態１において負荷に電圧源負荷が用いられた場合の電力変換装置の初期動作の第３の例について説明するための図である。FIG. 9 is a diagram for describing a third example of the initial operation of the power conversion device when the voltage source load is used as the load in the first embodiment. 実施の形態１に係る電力変換装置の変形例を示す図である。It is a figure which shows the modification of the power converter device which concerns on Embodiment 1. 実施の形態１に係る電力変換装置の他の変形例を示す図である。It is a figure which shows the other modification of the power converter device which concerns on Embodiment 1. 実施の形態２に係る電力変換装置の具体的な回路構成例を示す図である。It is a figure which shows the specific circuit structural example of the power converter device which concerns on Embodiment 2. 実施の形態２における電力変換装置の初期動作について説明するための図である。FIG. 9 is a diagram for explaining an initial operation of the power conversion device according to the second embodiment. 制御部の少なくとも一部の機能がソフトウェアで実現される例を示す図である。It is a figure which shows the example in which the at least one part function of a control part is implement|achieved by software.
　＜実施の形態１＞
　本発明の実施の形態１に係る電力変換装置について図面を参照して説明する。図１は、本発明の実施の形態１に係る電力変換装置を含む電源システムの概略構成を示す模式図である。図面および以下の説明において、同一または同様の構成要素を示す場合には同一の符号を付すものとする。 <Embodiment 1>
A power conversion device according to Embodiment 1 of the present invention will be described with reference to the drawings. 1 is a schematic diagram showing a schematic configuration of a power supply system including a power conversion device according to a first embodiment of the present invention. In the drawings and the following description, the same or similar components are designated by the same reference numerals.
　本発明の実施の形態１に示す電源システムは、電力変換装置１００、入力電源１および負荷７を備える。電力変換装置１００は、第１の電力変換回路２、第１の直流コンデンサ３、第２の電力変換回路４、第２の直流コンデンサ５、第３の電力変換回路６および制御部８を含む。第１の電力変換回路２の一端（入力端子）は、入力電源１に接続されている。第２の電力変換回路４の一端（入力端子）は、第１の電力変換回路２の他端（出力端子）に接続されている。第３の電力変換回路６の一端（入力端子）は、第２の電力変換回路４の他端（出力端子）に接続されている。第３の電力変換回路６の他端（出力端子）は、負荷７に接続されている。第１の電力変換回路２は、入力電源からの電圧を直流電圧へ変換する。第２の電力変換回路４は、第１の電力変換回路２からの直流電圧を絶縁トランスを介して変圧する。第３の電力変換回路６は、第２の電力変換回路４からの直流電圧を変換して負荷７に出力する。 The power supply system according to the first embodiment of the present invention includes a power conversion device 100, an input power supply 1 and a load 7. The power conversion device 100 includes a first power conversion circuit 2, a first DC capacitor 3, a second power conversion circuit 4, a second DC capacitor 5, a third power conversion circuit 6 and a control unit 8. One end (input terminal) of the first power conversion circuit 2 is connected to the input power supply 1. One end (input terminal) of the second power conversion circuit 4 is connected to the other end (output terminal) of the first power conversion circuit 2. One end (input terminal) of the third power conversion circuit 6 is connected to the other end (output terminal) of the second power conversion circuit 4. The other end (output terminal) of the third power conversion circuit 6 is connected to the load 7. The first power conversion circuit 2 converts the voltage from the input power supply into a DC voltage. The second power conversion circuit 4 transforms the DC voltage from the first power conversion circuit 2 through an insulation transformer. The third power conversion circuit 6 converts the DC voltage from the second power conversion circuit 4 and outputs it to the load 7.
　第１の直流コンデンサ３は、第１の電力変換回路２と第２の電力変換回路４とを接続する一対の第１の直流母線３１間に接続されており、第２の直流コンデンサ５は、第２の電力変換回路４と第３の電力変換回路６とを接続する一対の第２の直流母線５１間に接続されている。 The first DC capacitor 3 is connected between a pair of first DC buses 31 that connect the first power conversion circuit 2 and the second power conversion circuit 4, and the second DC capacitor 5 is It is connected between a pair of second DC buses 51 that connect the second power conversion circuit 4 and the third power conversion circuit 6.
　制御部８は、第１～第３の電力変換回路２，４，６の全てを制御可能であり、各電力変換回路が備える各スイッチング素子の制御を行う。この場合、制御部８は、後述の電流検出器および電圧検出器から得られる検出結果の一部または全部に基づいて、すべての電力変換回路が有する各スイッチング素子に対して駆動信号を送信し、スイッチング素子のオンオフを制御することにより所望の動作を実現する。 The control unit 8 can control all of the first to third power conversion circuits 2, 4, and 6, and controls each switching element included in each power conversion circuit. In this case, the control unit 8 transmits a drive signal to each switching element included in all power conversion circuits, based on a part or all of detection results obtained from a current detector and a voltage detector described later, A desired operation is realized by controlling ON/OFF of the switching element.
　本電源システムは、例えば、電動車両の充電器を中心とした電源システムに適用されるもので、入力電源１は商用交流系統もしくは自家発電機などの交流電源、またはバッテリなどの直流電源である。また、負荷７は、抵抗負荷または電圧源負荷である。抵抗負荷は、自発的に電圧を発生しない負荷であり、例えば照明機器や温調機器である。電圧源負荷は、自発的に電圧を発生する負荷であり、例えば車両走行用の高圧バッテリもしくは車両電装品の鉛バッテリなどである。なお、入力電源１や負荷７がこれらの例に限定されるものでないということはいうまでもない。 This power supply system is applied to, for example, a power supply system centering on a charger of an electric vehicle, and the input power supply 1 is an AC power supply such as a commercial AC system or a private generator, or a DC power supply such as a battery. The load 7 is a resistance load or a voltage source load. The resistive load is a load that does not spontaneously generate a voltage, and is, for example, a lighting device or a temperature control device. The voltage source load is a load that spontaneously generates a voltage, and is, for example, a high-voltage battery for vehicle running or a lead battery of vehicle electrical equipment. It goes without saying that the input power supply 1 and the load 7 are not limited to these examples.
　図２および図３は、実施の形態１に係る電力変換装置１００の具体的な回路構成例を示す図である。図２および図３の例では、入力電源１として交流電源が用いられる。また、図２の例では、負荷７として抵抗負荷が用いられ、図３の例では、負荷７として電圧源負荷が用いられる。電力変換装置１００の構成は、図２の例と図３の例とで同じである。 2 and 3 are diagrams showing a specific circuit configuration example of the power conversion apparatus 100 according to the first embodiment. In the example of FIGS. 2 and 3, an AC power supply is used as the input power supply 1. Further, in the example of FIG. 2, a resistive load is used as the load 7, and in the example of FIG. 3, a voltage source load is used as the load 7. The configuration of the power conversion device 100 is the same in the example of FIG. 2 and the example of FIG. 3.
　実施の形態１に係る電力変換装置１００は、第１の電力変換回路２として、入力電流を高力率に制御するＡＣ／ＤＣコンバータ２０を含み、第２の電力変換回路４として、直流電圧を変圧する絶縁型ＤＣ／ＤＣコンバータ４０を含み、第３の電力変換回路６として、直流電圧を変圧する非絶縁型のＤＣ／ＤＣコンバータ６０を含む。本例では、ＡＣ／ＤＣコンバータ２０が力率を改善するＰＦＣ（Ｐｏｗｅｒ　Ｆａｃｔｏｒ　Ｃｏｒｒｅｃｔｉｏｎ）に相当する。 The power conversion device 100 according to the first embodiment includes an AC/DC converter 20 that controls an input current to a high power factor as the first power conversion circuit 2, and a DC voltage as the second power conversion circuit 4. An insulating DC/DC converter 40 that transforms is included, and a non-insulating DC/DC converter 60 that transforms a DC voltage is included as the third power conversion circuit 6. In this example, the AC/DC converter 20 corresponds to a PFC (Power Factor Correction) that improves the power factor.
　図２および図３に示す第１の電力変換回路２（ＡＣ／ＤＣコンバータ２０）は、スイッチング素子２１～２４および力率改善用の交流リアクトル２１５、２１６を備える。スイッチング素子２１～２４はフルブリッジ型に接続されている。交流リアクトル２１５の一端は交流電源１１と接続されており、他端はスイッチング素子２１とスイッチング素子２２との接続点に接続されている。また、交流リアクトル２１６の一端は交流電源１１と接続されており、他端はスイッチング素子２３とスイッチング素子２４との接続点に接続されている。 The first power conversion circuit 2 (AC/DC converter 20) shown in FIGS. 2 and 3 includes switching elements 21 to 24 and power factor improving AC reactors 215 and 216. The switching elements 21 to 24 are connected in a full bridge type. One end of the AC reactor 215 is connected to the AC power supply 11, and the other end is connected to a connection point between the switching element 21 and the switching element 22. Further, one end of the AC reactor 216 is connected to the AC power supply 11, and the other end is connected to a connection point between the switching element 23 and the switching element 24.
　なお、図２および図３に示す第１の電力変換回路２では、交流リアクトル２１５、２１６が交流電源１１の両極側にそれぞれ接続されるが、片極側のみに接続されもよい。すなわち、交流リアクトル２１５，２１６のいずれか一方のみが用いられてもよい。 Note that in the first power conversion circuit 2 shown in FIGS. 2 and 3, the AC reactors 215 and 216 are connected to both sides of the AC power supply 11, respectively, but may be connected to only one side. That is, only one of AC reactors 215 and 216 may be used.
　また、図２および図３に示す第１の電力変換回路２は、全ての半導体素子にスイッチング素子を用いた構成であるが、ダイオードなどの受動半導体素子を用いたセミブリッジレス型、またはトーテムポール型の構成であってもよいことは言うまでもない。 The first power conversion circuit 2 shown in FIGS. 2 and 3 has a configuration in which switching elements are used for all semiconductor elements, but is a semi-bridgeless type or totem pole using passive semiconductor elements such as diodes. It goes without saying that it may be a mold configuration.
　図２および図３に示す第２の電力変換回路４（絶縁型ＤＣ／ＤＣコンバータ４０）は、絶縁トランス４９、１次側変換回路４Ａおよび２次側変換回路４Ｂを含む。絶縁トランス４９は、互いに磁気的に結合する２つの巻線を含む。絶縁トランス４９の一方の巻線は１次側変換回路４Ａの端子に接続され、他方の巻線は２次側変換回路４Ｂの端子に接続される。以下、１次側変換回路４Ａの端子に接続される巻線を１次側巻線と称し、２次側変換回路４Ｂの端子に接続される巻線を２次側巻線と称する。 The second power conversion circuit 4 (insulation type DC/DC converter 40) shown in FIGS. 2 and 3 includes an insulation transformer 49, a primary side conversion circuit 4A and a secondary side conversion circuit 4B. Isolation transformer 49 includes two windings that are magnetically coupled to each other. One winding of the isolation transformer 49 is connected to the terminal of the primary side conversion circuit 4A, and the other winding is connected to the terminal of the secondary side conversion circuit 4B. Hereinafter, the winding connected to the terminal of the primary side conversion circuit 4A is referred to as a primary side winding, and the winding connected to the terminal of the secondary side conversion circuit 4B is referred to as a secondary side winding.
　１次側変換回路４Ａは、スイッチング素子４１～４４を含む。スイッチング素子４１～４４はフルブリッジ型に接続されている。また、１次側変換回路４Ａの直流側の端子は、一対の第１の直流母線３１を介して第１の電力変換回路２および第１の直流コンデンサ３と接続されており、交流側の端子は絶縁トランス４９の１次側巻線と接続されている。この場合、直列接続されるスイッチング素子４１とスイッチング素子４２との接続点に絶縁トランス４９の１次側巻線の一端が接続され、直列接続されるスイッチング素子４３とスイッチング素子４４との接続点に絶縁トランス４９の１次側巻線の他端が接続される。 The primary side conversion circuit 4A includes switching elements 41 to 44. The switching elements 41 to 44 are connected in a full bridge type. Further, the DC side terminal of the primary side conversion circuit 4A is connected to the first power conversion circuit 2 and the first DC capacitor 3 via the pair of first DC bus lines 31, and the AC side terminal. Is connected to the primary winding of the insulating transformer 49. In this case, one end of the primary winding of the insulating transformer 49 is connected to the connection point between the switching elements 41 and 42 connected in series, and the connection point between the switching element 43 and switching element 44 connected in series is connected. The other end of the primary winding of the insulating transformer 49 is connected.
　絶縁トランス４９の２次側変換回路４Ｂは、スイッチング素子４５～４８を含む。スイッチング素子４５～４８はフルブリッジ型に接続されている。また、２次側変換回路４Ｂの直流側の端子は、一対の第２の直流母線５１を介して第２の直流コンデンサ５および第３の電力変換回路６と接続されており、交流側の端子は絶縁トランス４９の２次側巻線と接続されている。この場合、直列接続されるスイッチング素子４５とスイッチング素子４６との接続点に絶縁トランス４９の２次側巻線の一端が接続され、直列接続されるスイッチング素子４７とスイッチング素子４８との接続点に絶縁トランス４９の２次側巻線の他端が接続される。 The secondary side conversion circuit 4B of the isolation transformer 49 includes switching elements 45 to 48. The switching elements 45 to 48 are connected in a full bridge type. Further, the DC side terminal of the secondary side conversion circuit 4B is connected to the second DC capacitor 5 and the third power conversion circuit 6 via the pair of second DC bus lines 51, and the AC side terminal. Is connected to the secondary winding of the insulating transformer 49. In this case, one end of the secondary winding of the insulating transformer 49 is connected to the connection point between the switching elements 45 and 46 connected in series, and the connection point between the switching elements 47 and 48 connected in series is connected. The other end of the secondary winding of the insulating transformer 49 is connected.
　なお、第２の電力変換回路４が、絶縁トランス４９の１次側巻線もしくは２次側巻線に対して直列もしくは並列に接続されたリアクトル、コンデンサなどを含んでもよい。リアクトル、コンデンサなどを用いることにより、低損失なソフトスイッチング動作が可能となる。この場合、別個に用意されたリアクトルが絶縁トランス４９に外付けされてもよく、絶縁トランス４９の漏洩インダクタンスまたは励磁インダクタンスが、損失低減のためのリアクトルとして利用されてもよい。さらに、２次側変換回路４Ｂは、ダイオードを用いたダイオード整流回路で構成されてもよいし、コンデンサを用いた倍電圧整流回路で構成されてもよい。 Note that the second power conversion circuit 4 may include a reactor, a capacitor, etc. connected in series or in parallel with the primary winding or the secondary winding of the insulating transformer 49. By using a reactor and a capacitor, low-loss soft switching operation becomes possible. In this case, a separately prepared reactor may be externally attached to the insulating transformer 49, and the leakage inductance or the exciting inductance of the insulating transformer 49 may be used as a reactor for reducing loss. Further, the secondary side conversion circuit 4B may be configured by a diode rectifier circuit using a diode or a voltage doubler rectifier circuit using a capacitor.
　図２および図３に示す第３の電力変換回路６（ＤＣ／ＤＣコンバータ６０）は、スイッチング素子６１、６２、平滑用直流リアクトル６３および平滑用コンデンサ６４を含む。第３の電力変換回路６は、降圧チョッパの回路構成を有する。図２の例では、第３の電力変換回路６の出力端子に抵抗負荷７１が接続される。図３の例では、第３の電力変換回路６の出力端子に電圧源負荷７２が接続される。 The third power conversion circuit 6 (DC/DC converter 60) shown in FIGS. 2 and 3 includes switching elements 61 and 62, a smoothing DC reactor 63, and a smoothing capacitor 64. The third power conversion circuit 6 has a circuit configuration of a step-down chopper. In the example of FIG. 2, the resistive load 71 is connected to the output terminal of the third power conversion circuit 6. In the example of FIG. 3, the voltage source load 72 is connected to the output terminal of the third power conversion circuit 6.
　なお、図２および図３に示す第３の電力変換回路６は、降圧チョッパの回路構成を有するが、昇圧型や昇降圧型の回路構成を有してもよく、また、インターリーブの構成や並列接続構成を有してもよいことは言うまでもない。 Although the third power conversion circuit 6 shown in FIGS. 2 and 3 has a step-down chopper circuit configuration, it may have a step-up or step-up/step-down circuit configuration, and also has an interleave configuration or parallel connection. It goes without saying that it may have a configuration.
　第１の電力変換回路２のスイッチング素子２１～２４、第２の電力変換回路４のスイッチング素子４１～４８、および第３の電力変換回路６のスイッチング素子６１，６２としては、ＩＧＢＴ（Ｉｎｓｕｌａｔｅｄ　Ｇａｔｅ　Ｂｉｐｏｌａｒ　Ｔｒａｎｓｉｓｔｏｒ）、ＭＯＳＦＥＴ（Ｍｅｔａｌ　Ｏｘｉｄｅ　Ｓｅｍｉｃｏｎｄｕｃｔｏｒ　Ｆｉｅｌｄ　Ｅｆｆｅｃｔ　Ｔｒａｎｓｉｓｔｏｒ）、ＳｉＣ（Ｓｉｌｉｃｏｎ　Ｃａｒｂｉｄｅ）－ＭＯＳＦＥＴ、ＧａＮ（Ｇａｌｌｉｕｍ　Ｎｉｔｒｉｄｅ）－ＦＥＴ（Ｆｉｅｌｄ　Ｅｆｆｅｃｔ　Ｔｒａｎｓｉｓｔｏｒ）、またはＧａＮ－ＨＥＭＴ（Ｈｉｇｈ　Ｅｌｅｃｔｒｏｎ　Ｍｏｂｉｌｉｔｙ　Ｔｒａｎｓｉｓｔｏｒ）などを用いることができる。 As the switching elements 21 to 24 of the first power conversion circuit 2, the switching elements 41 to 48 of the second power conversion circuit 4, and the switching elements 61 and 62 of the third power conversion circuit 6, IGBTs (Insulated Gate Bipolar) are used. Transistor), MOSFET (Metal Oxide Semiconductor Field Effect Transistor), SiC (Silicon Carbide) (MOSFET), GaN (Galium Nitride Emitter) or FET (Field Effect Transistor), or GaN (Galium Nitride Emitter) (FET). ..
　電力変換装置１００は、電流検出器Ｄ１，Ｄ２および電圧検出器Ｄ３～Ｄ６をさらに備える。電流検出器Ｄ１は、交流電源１１から第１の電力変換回路２に流れる交流入力電流ｉａｃを検出する。電流検出器Ｄ２は、第３の電力変換回路６から負荷７に流れる直流出力電流Ｉｏｕｔを検出する。電圧検出器Ｄ３は、交流電源１１から第１の電力変換回路２に与えられる交流入力電圧ｖａｃを検出する。電圧検出器Ｄ４は、第１の直流コンデンサ３の電圧Ｖｌｉｎｋを検出する。電圧検出器Ｄ５は、第２の直流コンデンサ５の電圧Ｖｉｎｔを検出する。電圧検出器Ｄ６は、第３の電力変換回路６から負荷７に与えられる直流出力電圧Ｖｏｕｔとして、第３の電力変換回路６の平滑用コンデンサ６４の電圧を検出する。検出器Ｄ１～Ｄ６は、検出結果を制御部８に与える。制御部８は、与えられた検出値の一部または全部に基づいてフィードバック演算を行い、各スイッチング素子のオンオフを制御する。 The power conversion device 100 further includes current detectors D1 and D2 and voltage detectors D3 to D6. The current detector D1 detects an AC input current iac flowing from the AC power supply 11 to the first power conversion circuit 2. The current detector D2 detects the DC output current Iout flowing from the third power conversion circuit 6 to the load 7. The voltage detector D3 detects the AC input voltage vac applied to the first power conversion circuit 2 from the AC power supply 11. The voltage detector D4 detects the voltage Vlink of the first DC capacitor 3. The voltage detector D5 detects the voltage Vint of the second DC capacitor 5. The voltage detector D6 detects the voltage of the smoothing capacitor 64 of the third power conversion circuit 6 as the DC output voltage Vout given to the load 7 from the third power conversion circuit 6. The detectors D1 to D6 provide the detection result to the control unit 8. The control unit 8 performs feedback calculation based on a part or all of the given detection value to control ON/OFF of each switching element.
　電力変換装置１００の動作開始時には、制御部８は、初期動作として第１～第３の電力変換回路２，４，６が段階的に動作を開始するように、第１～第３の電力変換回路２，４，６を制御する。第１～第３の電力変換回路２，４，６の全てが動作を開始した後、制御部８は、定常動作を行うように第１～第３の電力変換回路２，４，６を制御する。ここで、動作の開始とは、該当の回路に含まれる少なくとも１つのスイッチング素子のスイッチング動作（オンオフ動作）が開始されることをいう。また、第１～第３の電力変換回路２，４，６が段階的に動作を開始するとは、少なくとも２つの電力変換回路が異なる時刻に動作を開始することをいう。 At the start of the operation of the power converter 100, the control unit 8 controls the first to third power converters so that the first to third power converter circuits 2, 4 and 6 start the operation stepwise as an initial operation. Control the circuits 2, 4, and 6. After all the first to third power conversion circuits 2, 4 and 6 start operating, the control unit 8 controls the first to third power conversion circuits 2, 4 and 6 so as to perform steady operation. To do. Here, the start of the operation means that the switching operation (ON/OFF operation) of at least one switching element included in the corresponding circuit is started. The fact that the first to third power conversion circuits 2, 4 and 6 start operating stepwise means that at least two power conversion circuits start operating at different times.
　まず、定常動作時における制御部８の役割について説明する。制御部８は、検出器Ｄ１～Ｄ６の検出結果に基づいて種々の出力値を演算し、その出力値に基づいて第１～第３の電力変換回路２，４，６を制御する。本例では、交流入力電流ｉａｃが予め定められた目標正弦波電流ｉａｃ＊に追従するように制御され、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが予め定められた目標直流電圧Ｖｌｉｎｋ＊に追従するように制御され、第２の直流コンデンサ５の電圧Ｖｉｎｔが予め定められた目標直流電圧Ｖｉｎｔ＊に追従するように制御される。また、負荷７として抵抗負荷７１が適用される場合に、直流出力電圧Ｖｏｕｔが予め定められた目標直流出力電圧Ｖｏｕｔ＊に追従するように制御され、負荷７として電圧源負荷７２が適用される場合に、直流出力電流Ｉｏｕｔが予め定められた目標直流出力電流Ｉｏｕｔ＊に追従するように制御される。 First, the role of the control unit 8 during steady operation will be described. The control unit 8 calculates various output values based on the detection results of the detectors D1 to D6, and controls the first to third power conversion circuits 2, 4, 6 based on the output values. In this example, the AC input current iac is controlled so as to follow a predetermined target sine wave current iac*, and the voltage Vlink of the first DC capacitor 3 follows the predetermined target DC voltage Vlink*. The voltage Vint of the second DC capacitor 5 is controlled so as to follow the predetermined target DC voltage Vint*. When the resistance load 71 is applied as the load 7, the DC output voltage Vout is controlled so as to follow a predetermined target DC output voltage Vout*, and the voltage source load 72 is applied as the load 7. In addition, the DC output current Iout is controlled so as to follow the predetermined target DC output current Iout*.
　具体的には、制御部８は、交流電圧ｖａｃの検出値と同期する正弦波状の電流指令（目標正弦波電流）ｉａｃ＊と、交流入力電流ｉａｃの検出値との電流差を算出する。制御部８は、算出した電流差をフィードバック量として比例制御または比例積分制御により出力値を演算する。 Specifically, the control unit 8 calculates the current difference between the sinusoidal current command (target sine wave current) iac* synchronized with the detected value of the AC voltage vac and the detected value of the AC input current iac. The control unit 8 calculates the output value by proportional control or proportional integral control with the calculated current difference as the feedback amount.
　また、制御部８は、目標直流電圧Ｖｌｉｎｋ＊と第１の直流コンデンサ３の直流電圧Ｖｌｉｎｋの検出値との電圧差を算出し、算出した電圧差をフィードバック量として比例制御または比例積分制御により出力値を演算する。 The control unit 8 also calculates the voltage difference between the target DC voltage Vlink* and the detected value of the DC voltage Vlink of the first DC capacitor 3, and outputs the calculated voltage difference as a feedback amount by proportional control or proportional-integral control. Calculate the value.
　また、制御部８は、目標直流電圧Ｖｉｎｔ＊と第２の直流コンデンサ５の直流電圧Ｖｉｎｔの検出値との電圧差を算出し、算出した電圧差をフィードバック量として比例制御または比例積分制御により出力値を演算する。 The control unit 8 also calculates the voltage difference between the target DC voltage Vint* and the detected value of the DC voltage Vint of the second DC capacitor 5, and outputs the calculated voltage difference as a feedback amount by proportional control or proportional-integral control. Calculate the value.
　また、負荷７として抵抗負荷７１が適用される場合に、制御部８は、目標直流出力電圧Ｖｏｕｔ＊と直流出力電圧Ｖｏｕｔの検出値との電圧差を算出し、算出した電圧差をフィードバック量として比例制御または比例積分制御により出力値を演算する。一方、負荷７として電圧源負荷７２が適用される場合に、制御部８は、目標直流出力電流Ｉｏｕｔ＊と直流出力電流Ｉｏｕｔの検出値との電圧差を算出し、算出した電圧差をフィードバック量として比例制御もしくは比例積分制御により出力値を演算する。 When the resistive load 71 is applied as the load 7, the control unit 8 calculates the voltage difference between the target DC output voltage Vout* and the detected value of the DC output voltage Vout, and uses the calculated voltage difference as the feedback amount. Output value is calculated by proportional control or proportional integral control. On the other hand, when the voltage source load 72 is applied as the load 7, the control unit 8 calculates the voltage difference between the target DC output current Iout* and the detected value of the DC output current Iout, and calculates the calculated voltage difference as the feedback amount. The output value is calculated by proportional control or proportional integral control.
　制御部８は、これらの出力値に基づいて、交流入力電流ｉａｃ、第１および第２の直流コンデンサ３，５の電圧Ｖｌｉｎｋ，Ｖｉｎｔならびに直流出力電圧Ｖｏｕｔ（または直流出力電流Ｉｏｕｔ）が上記目標値に追従するように、第１～第３の電力変換回路２，４，６を制御する。 Based on these output values, the control unit 8 determines that the AC input current iac, the voltages Vlink and Vint of the first and second DC capacitors 3 and 5 and the DC output voltage Vout (or the DC output current Iout) are the target values. The first to third power conversion circuits 2, 4 and 6 are controlled so as to follow.
　次に、電力変換装置１００の初期動作時における制御部８の役割について説明する。図４は、負荷７として抵抗負荷７１が用いられた場合の電力変換装置１００の初期動作についての説明するための図である。図４には、第１の直流コンデンサ３の電圧Ｖｌｉｎｋ、交流入力電圧ｖａｃ、交流入力電流ｉａｃ、第２の直流コンデンサ５の電圧Ｖｉｎｔ、および直流出力電圧Ｖｏｕｔの各々の検出値が示される。横軸は時間を表し、縦軸は電流または電圧を表す。また、下段に示される“１ｓｔ”は、第１の電力変換回路２の動作開始時刻を表し、“２ｎｄ”は、第２の電力変換回路４の動作開始時刻を表し、“３ｒｄ”は、第３の電力変換回路６の動作開始時刻を表す。 Next, the role of the control unit 8 during the initial operation of the power conversion device 100 will be described. FIG. 4 is a diagram for explaining the initial operation of the power conversion device 100 when the resistive load 71 is used as the load 7. FIG. 4 shows detected values of the voltage Vlink of the first DC capacitor 3, the AC input voltage vac, the AC input current iac, the voltage Vint of the second DC capacitor 5, and the DC output voltage Vout. The horizontal axis represents time, and the vertical axis represents current or voltage. Further, "1st" shown in the lower stage represents the operation start time of the first power conversion circuit 2, "2nd" represents the operation start time of the second power conversion circuit 4, and "3rd" represents the operation start time. 3 represents the operation start time of the power conversion circuit 6 of No. 3.
　図４の例において、電力変換装置１００が非動作状態である時刻を初期時刻ｔ０と定義する。すなわち、時刻ｔ０にて、第１の電力変換回路２、第２の電力変換回路４および第３の電力変換回路６のスイッチング動作はいずれも停止されている。また、時刻ｔ０にて、第１の直流コンデンサ３の電圧Ｖｌｉｎｋおよび第２の直流コンデンサ５の電圧Ｖｉｎｔはそれぞれ０である。 In the example of FIG. 4, the time when the power conversion device 100 is in the non-operating state is defined as the initial time t0. That is, at time t0, the switching operations of the first power conversion circuit 2, the second power conversion circuit 4, and the third power conversion circuit 6 are all stopped. At time t0, the voltage Vlink of the first DC capacitor 3 and the voltage Vint of the second DC capacitor 5 are 0, respectively.
　制御部８は、検出器Ｄ１～Ｄ６による検出結果に基づいて、第１の直流コンデンサ３の電圧Ｖｌｉｎｋ、第２の直流コンデンサ５の電圧Ｖｉｎｔおよび直流出力電圧Ｖｏｕｔが以下のように変化するように、第１～第３の電力変換回路２，４，６を制御する。 The controller 8 controls the voltage Vlink of the first DC capacitor 3, the voltage Vint of the second DC capacitor 5, and the DC output voltage Vout to change as follows based on the detection results of the detectors D1 to D6. , And controls the first to third power conversion circuits 2, 4, and 6.
　時刻ｔ１にて、交流入力電圧ｖａｃが第１の電力変換回路２の入力端子に印加される。このとき、第１の電力変換回路２の各スイッチング素子の内蔵ダイオードまたは外付けのダイオードを介して第１の直流コンデンサ３が受動的に充電される。それにより、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが初期充電電圧Ｖｌｉｎｋ０に上昇する。なお、初期充電電圧Ｖｌｉｎｋ０は、交流入力電圧ｖａｃの実効値Ｖａｃ，ｒｍｓに対して式（１）を満たす。なお、式（１）における「√２Ｖａｃ，ｒｍｓ」は、交流入力電圧ｖａｃの最大値に相当する。
Figure JPOXMLDOC01-appb-I000001
At time t1, the AC input voltage vac is applied to the input terminal of the first power conversion circuit 2. At this time, the first DC capacitor 3 is passively charged via the built-in diode of each switching element of the first power conversion circuit 2 or the external diode. As a result, the voltage Vlink of the first DC capacitor 3 rises to the initial charging voltage Vlink0. The initial charging voltage Vlink0 satisfies the equation (1) with respect to the effective values Vac and rms of the AC input voltage vac. Note that “√2Vac,rms” in the equation (1) corresponds to the maximum value of the AC input voltage vac.
Figure JPOXMLDOC01-appb-I000001
　時刻ｔ２にて、第１の電力変換回路２のスイッチング動作が開始される。この場合、第１の電力変換回路２の実効デューティ比が徐々に上昇されることにより、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが徐々に上昇する。それにより、急激な電圧変化が防止される。この時点では、第２の電力変換回路４および第３の電力変換回路６のスイッチング動作は停止されている。 At time t2, the switching operation of the first power conversion circuit 2 is started. In this case, the effective duty ratio of the first power conversion circuit 2 is gradually increased, so that the voltage Vlink of the first DC capacitor 3 is gradually increased. Thereby, abrupt voltage change is prevented. At this point, the switching operations of the second power conversion circuit 4 and the third power conversion circuit 6 are stopped.
　時刻ｔ３にて、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが、予め定められた第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達する。このとき、第１の電力変換回路２による交流入力電流ｉａｃの力率制御が開始されるとともに、第２の電力変換回路４のスイッチング動作が開始される。これにより、第１の直流コンデンサ３から第２の電力変換回路４を介して第２の直流コンデンサ５に電流が流れ、第２の直流コンデンサ５の充電が開始される。 At time t3, the voltage Vlink of the first DC capacitor 3 reaches the predetermined first threshold voltage Vlink,th. At this time, the power factor control of the AC input current iac by the first power conversion circuit 2 is started, and the switching operation of the second power conversion circuit 4 is started. As a result, current flows from the first DC capacitor 3 to the second DC capacitor 5 via the second power conversion circuit 4, and charging of the second DC capacitor 5 is started.
　第１の閾値電圧Ｖｌｉｎｋ，ｔｈは、式（２）の条件を満たす。
Figure JPOXMLDOC01-appb-I000002
The first threshold voltage Vlink,th satisfies the condition of Expression (2).
Figure JPOXMLDOC01-appb-I000002
　ここで、第１の電力変換回路２の動作中に、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが交流入力電圧ｖａｃより低くなると、第１の電力変換回路２が正常動作（昇圧動作）を継続することができなくなる。具体的には、スイッチング素子２１～２４のオンオフに関係なく、交流電源１１と第１の直流コンデンサ３との間の電流経路が固定される。そのため、第１の直流コンデンサ３の電圧Ｖｌｉｎｋは、交流入力電圧ｖａｃの最大値以上に維持される必要がある。 Here, when the voltage Vlink of the first DC capacitor 3 becomes lower than the AC input voltage vac during the operation of the first power conversion circuit 2, the first power conversion circuit 2 continues the normal operation (boosting operation). Can't do it. Specifically, the current path between the AC power supply 11 and the first DC capacitor 3 is fixed regardless of whether the switching elements 21 to 24 are turned on or off. Therefore, the voltage Vlink of the first DC capacitor 3 needs to be maintained at or above the maximum value of the AC input voltage vac.
　上記のように、第１の直流コンデンサ３の初期充電電圧Ｖｌｉｎｋ０は交流入力電圧ｖａｃの最大値（√２Ｖａｃ，ｒｍｓ）以上であり、第２の電力変換回路４の動作開始前には、第１の直流コンデンサ３の電圧Ｖｌｉｎｋは交流入力電圧ｖａｃ以上に維持される。しかしながら、第２の電力変換回路４の動作が開始されると、第１の直流コンデンサ３から第２の直流コンデンサ５に電流が流れることによって第１の直流コンデンサ３の電圧Ｖｌｉｎｋが低下し、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが交流入力電圧ｖａｃの最大値よりも低くなる可能性がある。 As described above, the initial charging voltage Vlink0 of the first DC capacitor 3 is equal to or higher than the maximum value (√2Vac, rms) of the AC input voltage vac, and before the operation of the second power conversion circuit 4 starts, The voltage Vlink of the DC capacitor 3 is maintained above the AC input voltage vac. However, when the operation of the second power conversion circuit 4 is started, a current flows from the first DC capacitor 3 to the second DC capacitor 5, so that the voltage Vlink of the first DC capacitor 3 decreases, and The voltage Vlink of the DC capacitor 3 of No. 1 may be lower than the maximum value of the AC input voltage vac.
　そこで、本実施の形態では、第１の電力変換回路２によって第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈまで上昇されてから第２の電力変換回路４のスイッチング動作が開始される。これにより、第１の直流コンデンサ３の電圧Ｖｌｉｎｋと交流入力電圧ｖａｃとの間に一定のマージン（余裕）を確保した状態で、第２の電力変換回路４のスイッチング動作を開始させることができる。また、本実施の形態では、第２の電力変換回路４の実効デューティ比は０から徐々に増加され、第１の直流コンデンサ３から第２の直流コンデンサ５に流れる電流は０から徐々に増加する。それにより、第２の電力変換回路４の動作開始に伴う第１の直流コンデンサ３の電圧Ｖｌｉｎｋの急峻な低下が抑制される。 Therefore, in the present embodiment, the switching operation of the second power conversion circuit 4 is performed after the voltage Vlink of the first DC capacitor 3 is raised to the first threshold voltage Vlink,th by the first power conversion circuit 2. Be started. As a result, the switching operation of the second power conversion circuit 4 can be started in a state where a certain margin is secured between the voltage Vlink of the first DC capacitor 3 and the AC input voltage vac. Further, in the present embodiment, the effective duty ratio of the second power conversion circuit 4 is gradually increased from 0, and the current flowing from the first DC capacitor 3 to the second DC capacitor 5 is gradually increased from 0. .. As a result, a sharp decrease in the voltage Vlink of the first DC capacitor 3 due to the start of the operation of the second power conversion circuit 4 is suppressed.
　なお、「デューティ比が徐々に上昇する」とは、図４の例のようにデューティ比が一定の変化率で直線的かつ連続的に上昇する場合に限らず、デューティ比が曲線的かつ連続的に上昇する場合、およびデューティ比が複数ステップを介して段階的に上昇する場合を含む。ただし、デューティ比が段階的に上昇される場合には、ステップ数が十分に多く設定され、１ステップでの変化幅が極力小さいことが好ましい。 Note that "the duty ratio gradually increases" is not limited to the case where the duty ratio linearly and continuously increases at a constant rate of change as in the example of Fig. 4, and the duty ratio is curvilinear and continuous. And the case where the duty ratio increases stepwise through a plurality of steps. However, when the duty ratio is increased stepwise, it is preferable that the number of steps is set sufficiently large and the change width in one step is as small as possible.
　これらにより、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが交流入力電圧ｖａｃの最大値より低くなることが防止され、第１の電力変換回路２が安定的に正常動作を継続することができる。 With these, the voltage Vlink of the first DC capacitor 3 is prevented from becoming lower than the maximum value of the AC input voltage vac, and the first power conversion circuit 2 can stably continue normal operation.
　また、第１の閾値電圧Ｖｌｉｎｋ，ｔｈが目標直流電圧Ｖｌｉｎｋ＊より小さい値に設定されているため、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが過電圧となることが防止されるとともに、第２の電力変換回路４の動作開始までの時間を短くすることができる。 Further, since the first threshold voltage Vlink,th is set to a value smaller than the target DC voltage Vlink*, the voltage Vlink of the first DC capacitor 3 is prevented from becoming an overvoltage, and the second power is reduced. The time until the operation of the conversion circuit 4 starts can be shortened.
　さらに、時刻ｔ３にて、第２の電力変換回路４のスイッチング動作が開始されると同時に、第１の電力変換回路２による力率制御が開始される。これにより、交流入力電流ｉａｃの大きさ（振幅）を０から最大値まで徐々に増加させることができる。したがって、第１および第２の直流コンデンサ３，５を安定的に充電することができる。 Further, at time t3, the switching operation of the second power conversion circuit 4 is started, and at the same time, the power factor control by the first power conversion circuit 2 is started. Thereby, the magnitude (amplitude) of the AC input current iac can be gradually increased from 0 to the maximum value. Therefore, the first and second DC capacitors 3 and 5 can be stably charged.
　その後、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが目標直流電圧Ｖｌｉｎｋ＊に達すると、目標直流電圧Ｖｌｉｎｋ＊に追従するように電圧Ｖｌｉｎｋが制御される。なお、時刻ｔ３にて第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達した時点から第１の直流コンデンサ３の電圧Ｖｌｉｎｋが目標直流電圧Ｖｌｉｎｋ＊に追従するように制御されてもよい。 After that, when the voltage Vlink of the first DC capacitor 3 reaches the target DC voltage Vlink*, the voltage Vlink is controlled so as to follow the target DC voltage Vlink*. Control is performed such that the voltage Vlink of the first DC capacitor 3 reaches the first threshold voltage Vlink,th at time t3, and the voltage Vlink of the first DC capacitor 3 follows the target DC voltage Vlink*. May be done.
　時刻ｔ４にて、第２の直流コンデンサ５の電圧Ｖｉｎｔが、予め定められた第２の閾値電圧Ｖｉｎｔ，ｔｈに達すると、第１の電力変換回路２および第２の電力変換回路４に加えて、第３の電力変換回路６のスイッチング動作が開始される。これにより、第２の直流コンデンサ５から第３の電力変換回路６を介して抵抗負荷７１に電流が流れ、抵抗負荷７１に電力が供給される。 At time t4, when the voltage Vint of the second DC capacitor 5 reaches the predetermined second threshold voltage Vint,th, in addition to the first power conversion circuit 2 and the second power conversion circuit 4, , The switching operation of the third power conversion circuit 6 is started. As a result, current flows from the second DC capacitor 5 to the resistance load 71 via the third power conversion circuit 6, and power is supplied to the resistance load 71.
　ここで、第２の閾値電圧Ｖｉｎｔ，ｔｈは、式（３）の条件を満たす。
Figure JPOXMLDOC01-appb-I000003
Here, the second threshold voltage Vint,th satisfies the condition of Expression (3).
Figure JPOXMLDOC01-appb-I000003
　ここで、第３の電力変換回路６の動作中に、第２の直流コンデンサ５の電圧Ｖｉｎｔが抵抗負荷７１に出力される直流出力電圧Ｖｏｕｔよりも低くなると、第３の電力変換回路６が正常動作（降圧動作）を継続することができなくなる。具体的には、第３の電力変換回路６のディーティー比が０に設定されることにより、スイッチング素子６１が常時オフされ、抵抗負荷７１への電力供給が不可能な状態となる。したがって、第２の直流コンデンサ５の電圧Ｖｉｎｔは、直流出力電圧Ｖｏｕｔよりも高く維持される必要がある。 Here, when the voltage Vint of the second DC capacitor 5 becomes lower than the DC output voltage Vout output to the resistive load 71 during the operation of the third power conversion circuit 6, the third power conversion circuit 6 operates normally. It becomes impossible to continue the operation (step-down operation). Specifically, by setting the duty ratio of the third power conversion circuit 6 to 0, the switching element 61 is constantly turned off, and power cannot be supplied to the resistive load 71. Therefore, the voltage Vint of the second DC capacitor 5 needs to be maintained higher than the DC output voltage Vout.
　本実施の形態では、第２の電力変換回路４によって第２の直流コンデンサ５の電圧Ｖｉｎｔが第２の閾値電圧Ｖｉｎｔ，ｔｈまで上昇されてから第３の電力変換回路６の動作が開始される。これにより、第２の直流コンデンサ５の電圧Ｖｉｎｔと直流出力電圧Ｖｏｕｔとの間に一定のマージンを確保した状態で、第３の電力変換回路６のスイッチング動作を開始させることができる。また、第３の電力変換回路６の実効デューティ比は０から徐々に増加され、第２の直流コンデンサ５から抵抗負荷７１に流れる電流は０から徐々に増加する。それにより、第３の電力変換回路６の動作開始に伴う第２の直流コンデンサ５の電圧Ｖｉｎｔの急峻な低下が抑制される。その結果、第２の直流コンデンサ５の電圧Ｖｉｎｔが直流出力電圧Ｖｏｕｔより低くなることが防止され、第３の電力変換回路６が安定的に正常動作を継続することができる。 In the present embodiment, the operation of the third power conversion circuit 6 is started after the voltage Vint of the second DC capacitor 5 is raised to the second threshold voltage Vint,th by the second power conversion circuit 4. .. As a result, the switching operation of the third power conversion circuit 6 can be started with a certain margin secured between the voltage Vint of the second DC capacitor 5 and the DC output voltage Vout. Further, the effective duty ratio of the third power conversion circuit 6 is gradually increased from 0, and the current flowing from the second DC capacitor 5 to the resistive load 71 is gradually increased from 0. As a result, a sharp drop in the voltage Vint of the second DC capacitor 5 due to the start of the operation of the third power conversion circuit 6 is suppressed. As a result, the voltage Vint of the second DC capacitor 5 is prevented from becoming lower than the DC output voltage Vout, and the third power conversion circuit 6 can stably continue normal operation.
　その後、第２の直流コンデンサ５の電圧Ｖｉｎｔが目標直流電圧Ｖｉｎｔ＊に達すると、目標直流電圧Ｖｉｎｔ＊に追従するように電圧Ｖｉｎｔが制御される。なお、時刻ｔ４にて第２の直流コンデンサ５の電圧Ｖｉｎｔが第２の閾値電圧Ｖｉｎｔ，ｔｈに達した時点から第２の直流コンデンサ５の電圧Ｖｉｎｔが目標直流電圧Ｖｉｎｔ＊に追従するように制御されてもよい。 After that, when the voltage Vint of the second DC capacitor 5 reaches the target DC voltage Vint*, the voltage Vint is controlled so as to follow the target DC voltage Vint*. Control is performed such that the voltage Vint of the second DC capacitor 5 follows the target DC voltage Vint* from the time when the voltage Vint of the second DC capacitor 5 reaches the second threshold voltage Vint,th at time t4. May be done.
　なお、図４には、抵抗負荷７１に供給される電力の変化として直流出力電圧Ｖｏｕｔの変化のみが示されるが、直流出力電流Ｉｏｕｔも直流出力電圧Ｖｏｕｔの上昇に伴って増加する。上記のように、負荷７として抵抗負荷７１が用いられる場合には、直流出力電流Ｉｏｕｔの検出値ではなく直流出力電圧Ｖｏｕｔの検出値が用いてスイッチング素子のオンオフ制御が行われるので、図４では直流出力電流Ｉｏｕｔの図示を省略している。 Although FIG. 4 shows only the change in the DC output voltage Vout as the change in the power supplied to the resistive load 71, the DC output current Iout also increases as the DC output voltage Vout increases. As described above, when the resistive load 71 is used as the load 7, the on/off control of the switching element is performed using the detected value of the DC output voltage Vout instead of the detected value of the DC output current Iout. Illustration of the DC output current Iout is omitted.
　時刻ｔ５で電圧Ｖｏｕｔが目標直流出力電圧Ｖｏｕｔ＊に達すると、第１の電力変換回路２、第２の電力変換回路４および第３の電力変換回路６の全てが上記の定常動作に移行する。 When the voltage Vout reaches the target DC output voltage Vout* at time t5, all of the first power conversion circuit 2, the second power conversion circuit 4, and the third power conversion circuit 6 shift to the above-mentioned steady operation.
　このように、負荷７として抵抗負荷７１が用いられた図４の例では、第１～第３の電力変換回路２，４，６の動作が順に開始されることにより、第１および第２の直流コンデンサ３，５が順に充電される。これにより、第１～第３の電力変換回路２，４，６の動作が同時に開始される場合と異なり、第１～第３の電力変換回路２，４，６内における過電流ならびに第１および第２の直流コンデンサ３，５の過電圧を発生させることなく、負荷７への電力供給を安定的に開始することができる。 As described above, in the example of FIG. 4 in which the resistive load 71 is used as the load 7, the operations of the first to third power conversion circuits 2, 4, and 6 are sequentially started, so that the first and second power conversion circuits are started. The DC capacitors 3 and 5 are sequentially charged. As a result, unlike the case where the operations of the first to third power conversion circuits 2, 4, and 6 are simultaneously started, the overcurrent in the first to third power conversion circuits 2, 4, and 6 The power supply to the load 7 can be stably started without generating the overvoltage of the second DC capacitors 3 and 5.
　仮に、第１～第３の電力変換回路２，４，６の動作が同時に開始されると、第１および第２の直流コンデンサ３，５、ならびに負荷７に同時に電圧が印加される。この場合、第１および第２の直流コンデンサ３，５の電圧を個別に制御することは困難であり、第１および第２の直流コンデンサ３，５の少なくも１つに対して瞬間的に大きな電流が流れ込む。それにより、第１～第３の電力変換回路２，４，６内で過電流が発生するとともに第１および第２の直流コンデンサ３，５が過電圧となる可能性がある。 If the operations of the first to third power conversion circuits 2, 4 and 6 are started at the same time, the voltage is applied to the first and second DC capacitors 3 and 5 and the load 7 at the same time. In this case, it is difficult to individually control the voltages of the first and second DC capacitors 3 and 5, and the voltage is instantaneously larger than at least one of the first and second DC capacitors 3 and 5. The current flows in. As a result, an overcurrent may occur in the first to third power conversion circuits 2, 4, 6 and the first and second DC capacitors 3, 5 may become overvoltage.
　それに対して、第１～第３の電力変換回路２，４，６の動作が順に開始される場合には、第１および第２の直流コンデンサ３，５の電圧を個別に制御することができる。具体的には、第２の電力変換回路４の動作が停止された状態で第１の電力変換回路２のデューティ比を調整することにより、第１の直流コンデンサ３の電圧Ｖｌｉｎｋを制御することができる。また、第３の電力変換回路６の動作が停止された状態で第２の電力変換回路４のデューティ比を調整することにより、第２の直流コンデンサ５の電圧Ｖｉｎｔを制御することができる。したがって、第１および第２の直流コンデンサ３，５の電圧を安定的に上昇させることができる。 On the other hand, when the operations of the first to third power conversion circuits 2, 4, and 6 are sequentially started, the voltages of the first and second DC capacitors 3 and 5 can be individually controlled. .. Specifically, the voltage Vlink of the first DC capacitor 3 can be controlled by adjusting the duty ratio of the first power conversion circuit 2 while the operation of the second power conversion circuit 4 is stopped. it can. Further, the voltage Vint of the second DC capacitor 5 can be controlled by adjusting the duty ratio of the second power conversion circuit 4 while the operation of the third power conversion circuit 6 is stopped. Therefore, the voltage of the first and second DC capacitors 3 and 5 can be stably increased.
　その後、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達しかつ第２の直流コンデンサ５の電圧Ｖｉｎｔが第２の閾値電圧Ｖｉｎｔ，ｔｈに達した状態で、第３の電力変換回路６の動作が開始されることにより、第１～第３の電力変換回路２，４，６内における過電流ならびに第１および第２の直流コンデンサ３，５の過電圧を発生させることなく、電力変換装置１００から負荷７への電力供給を安定的に開始させることができる。 After that, in a state where the voltage Vlink of the first DC capacitor 3 reaches the first threshold voltage Vlink,th and the voltage Vint of the second DC capacitor 5 reaches the second threshold voltage Vint,th, Since the operation of the power conversion circuit 6 is started, overcurrent in the first to third power conversion circuits 2, 4 and 6 and overvoltage of the first and second DC capacitors 3 and 5 are not generated. The power supply from the power converter 100 to the load 7 can be stably started.
　なお、図４の例では、電圧Ｖｌｉｎｋが０から第１の閾値電圧Ｖｌｉｎｋ，ｔｈに至るまでの期間と、電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈから目標直流電圧Ｖｌｉｎｋ＊に至るまでの期間とで、電圧Ｖｌｉｎｋの変化率（傾き）が異なるが、電圧Ｖｌｉｎｋが０から目標直流電圧Ｖｌｉｎｋ＊に至るまで、電圧Ｖｌｉｎｋの変化率が一定であってもよい。同様に、電圧Ｖｉｎｔが０から第２の閾値電圧Ｖｉｎｔ，ｔｈに至るまでの期間と、電圧Ｖｉｎｔが第２の閾値電圧Ｖｉｎｔ，ｔｈから目標直流電圧Ｖｉｎｔ＊に至るまでの期間とで、電圧Ｖｉｎｔの変化率が異なるが、電圧Ｖｉｎｔが０から目標直流電圧Ｖｉｎｔ＊に至るまで、電圧Ｖｉｎｔの変化率が一定であってもよい。また、電圧Ｖｌｉｎｋおよび電圧Ｖｉｎｔがそれぞれ連続的に変化するのではなく、複数ステップを介して段階的に変化してもよい。ただし、過電流および過電圧の発生を効果的に防止するためには、ステップ数が十分に多く設定され、１ステップでの電圧変化幅が極力小さいことが好ましい。 In the example of FIG. 4, the period from when the voltage Vlink reaches 0 to the first threshold voltage Vlink,th and the period from when the voltage Vlink reaches the target DC voltage Vlink* from the first threshold voltage Vlink,th. Although the rate of change (gradient) of the voltage Vlink is different, the rate of change of the voltage Vlink may be constant from the voltage Vlink of 0 to the target DC voltage Vlink*. Similarly, the voltage Vint is divided into a period from the voltage Vint reaching 0 to the second threshold voltage Vint,th and a period from the voltage Vint reaching the second threshold voltage Vint,th to the target DC voltage Vint*. However, the rate of change of the voltage Vint may be constant from the voltage Vint of 0 to the target DC voltage Vint*. Further, the voltage Vlink and the voltage Vint may not change continuously, but may change stepwise through a plurality of steps. However, in order to effectively prevent the occurrence of overcurrent and overvoltage, it is preferable that the number of steps is set sufficiently large and the voltage change width in one step is as small as possible.
　図５は、負荷７に電圧源負荷７２が適用された場合における電力変換装置１００の初期動作の第１の例について説明するための図である。図５には、図４の例と同様に、電圧Ｖｌｉｎｋ，ｖａｃ，Ｖｉｎｔ，Ｖｏｕｔおよび電流ｉａｃの検出値が示されるとともに、直流出力電流Ｉｏｕｔの検出値が示される。上記のように、負荷７として電圧源負荷７２が用いられる場合には、直流出力電流Ｉｏｕｔの検出値を用いてスイッチング素子のオンオフ制御が行われる。 FIG. 5 is a diagram for explaining a first example of the initial operation of the power conversion device 100 when the voltage source load 72 is applied to the load 7. Similar to the example of FIG. 4, FIG. 5 shows the detected values of the voltages Vlink, vac, Vint, Vout and the current iac, as well as the detected values of the DC output current Iout. As described above, when the voltage source load 72 is used as the load 7, the on/off control of the switching element is performed using the detected value of the DC output current Iout.
　図５の例では、電圧源負荷７２が一定の直流電圧を発生させる。そのため、電力変換装置１００が非動作状態である時刻ｔ０において、電圧源負荷７２による直流電圧が第３の電力変換回路６の出力端子に印加されている。この電圧は電圧Ｖｏｕｔとして検出される。この場合、第３の電力変換回路６のスイッチング素子の内蔵ダイオードもしくは外付けのダイオードを介して第２の直流コンデンサ５が受動的に充電される。それにより、第２の直流コンデンサ５の電圧Ｖｉｎｔが初期充電電圧Ｖｉｎｔ０に維持されている。 In the example of FIG. 5, the voltage source load 72 generates a constant DC voltage. Therefore, at time t0 when the power conversion device 100 is in the non-operating state, the DC voltage from the voltage source load 72 is applied to the output terminal of the third power conversion circuit 6. This voltage is detected as the voltage Vout. In this case, the second DC capacitor 5 is passively charged through the built-in diode of the switching element of the third power conversion circuit 6 or the external diode. As a result, the voltage Vint of the second DC capacitor 5 is maintained at the initial charging voltage Vint0.
　図４の例と同様に、時刻ｔ１にて、交流入力電圧ｖａｃが第１の電力変換回路２の入力端子に印加される。それにより、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが初期充電電圧Ｖｌｉｎｋ０に上昇する。時刻ｔ２にて、第１の電力変換回路２のスイッチング動作が開始される。この場合、第１の電力変換回路２の実効デューティ比が徐々に上昇されることにより、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが徐々に上昇する。 Similar to the example of FIG. 4, the AC input voltage vac is applied to the input terminal of the first power conversion circuit 2 at time t1. As a result, the voltage Vlink of the first DC capacitor 3 rises to the initial charging voltage Vlink0. At time t2, the switching operation of the first power conversion circuit 2 is started. In this case, the effective duty ratio of the first power conversion circuit 2 is gradually increased, so that the voltage Vlink of the first DC capacitor 3 is gradually increased.
　時刻ｔ３にて、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達すると、第１の電力変換回路２による交流電流ｉａｃの力率制御が開始されるとともに、第２の電力変換回路４のスイッチング動作が開始される。これにより、第１の直流コンデンサ３から第２の電力変換回路４を介して第２の直流コンデンサ５に電流が流れ、第２の直流コンデンサ５の充電が開始される。この場合、第２の電力変換回路４の実効デューティ比は、０から徐々に増加される。それにより、電圧Ｖｉｎｔが初期充電電圧Ｖｉｎｔ０から徐々に上昇する。 At time t3, when the voltage Vlink of the first DC capacitor 3 reaches the first threshold voltage Vlink,th, the power factor control of the alternating current iac by the first power conversion circuit 2 is started, and the second The switching operation of the power conversion circuit 4 is started. As a result, current flows from the first DC capacitor 3 to the second DC capacitor 5 via the second power conversion circuit 4, and charging of the second DC capacitor 5 is started. In this case, the effective duty ratio of the second power conversion circuit 4 is gradually increased from 0. As a result, the voltage Vint gradually rises from the initial charging voltage Vint0.
　なお、本例では、電圧源負荷７２によって第２の直流コンデンサ５の電圧Ｖｉｎｔが初期充電電圧Ｖｉｎｔ０に充電されているので、第２の直流コンデンサ５の電圧Ｖｉｎｔが０である場合と比べて、第１の直流コンデンサ３から第２の直流コンデンサ５に流れる電流が抑制される。そこで、第１の電力変換回路２が正常動作を継続することができる範囲内（第１の直流コンデンサ３の電圧ｌｉｎｋが交流入力電圧ｖａｃよりも低くならない範囲内）で、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達する前に第２の電力変換回路４のスイッチング動作が開始されてもよい。 In this example, since the voltage Vint of the second DC capacitor 5 is charged to the initial charging voltage Vint0 by the voltage source load 72, compared to the case where the voltage Vint of the second DC capacitor 5 is 0, The current flowing from the first DC capacitor 3 to the second DC capacitor 5 is suppressed. Therefore, within the range in which the first power conversion circuit 2 can continue normal operation (within the range in which the voltage link of the first DC capacitor 3 does not become lower than the AC input voltage vac), the first DC capacitor 3 The switching operation of the second power conversion circuit 4 may be started before the voltage Vlink reaches the first threshold voltage Vlink,th.
　時刻ｔ４ａにて、第２の直流コンデンサ５の電圧Ｖｉｎｔが第２の閾値電圧Ｖｉｎｔ，ｔｈに達すると、第１の電力変換回路２および第２の電力変換回路４に加えて、第３の電力変換回路６のスイッチング動作が開始され、第３の電力変換回路６から抵抗負荷７１に電力が供給される。この場合、第３の電力変換回路６の実効デューティ比が０から徐々に増加されることにより、電圧源負荷７２に与えられる直流電流Ｉｏｕｔが０から徐々に上昇する。すなわち、電圧源負荷７２に与えられる電力が０から徐々に上昇する。 At time t4a, when the voltage Vint of the second DC capacitor 5 reaches the second threshold voltage Vint,th, the third power is added to the first power conversion circuit 2 and the second power conversion circuit 4. The switching operation of the conversion circuit 6 is started, and power is supplied from the third power conversion circuit 6 to the resistance load 71. In this case, the effective duty ratio of the third power conversion circuit 6 is gradually increased from 0, so that the DC current Iout given to the voltage source load 72 is gradually increased from 0. That is, the electric power applied to the voltage source load 72 gradually increases from zero.
　直流出力電流Ｉｏｕｔが目標直流出力電流Ｉｏｕｔ＊まで達した時刻ｔ５ａにて、第１の電力変換回路２、第２の電力変換回路４、および第３の電力変換回路６の全てが定常動作に移行する。 At time t5a when the DC output current Iout reaches the target DC output current Iout*, all of the first power conversion circuit 2, the second power conversion circuit 4, and the third power conversion circuit 6 shift to steady operation. To do.
　このように、負荷７として電圧源負荷７２が用いられた図５の例においても、第１～第３の電力変換回路２，４，６の動作が順に開始されることにより、第１および第２の直流コンデンサ３，５の電圧Ｖｌｉｎｋ，Ｖｉｎｔを個別に精度良く制御することができる。その結果、第１～第３の電力変換回路２，４，６内における過電流ならびに第１および第２の直流コンデンサ３，５の過電圧を発生させることなく、電力変換装置１００から負荷７への電力供給を安定的に開始することができる。 As described above, also in the example of FIG. 5 in which the voltage source load 72 is used as the load 7, the first to third power conversion circuits 2, 4, and 6 are started in order, so that the first and the second power conversion circuits are started. The voltages Vlink and Vint of the two DC capacitors 3 and 5 can be individually and accurately controlled. As a result, the power converter 100 transfers the load 7 to the load 7 without generating an overcurrent in the first to third power conversion circuits 2, 4 and 6 and an overvoltage in the first and second DC capacitors 3 and 5. The power supply can be stably started.
　また、図４の例と同様に、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達したときに第２の電力変換回路４のスイッチング動作が開始され、かつ第２の電力変換回路４の実効デューティ比が０から徐々に上昇される。それにより、第１の直流コンデンサ３の電圧ｌｉｎｋが交流入力電圧ｖａｃの最大値より低くなることが防止され、第１の電力変換回路２が安定的に正常動作を継続することができる。 Further, similar to the example of FIG. 4, when the voltage Vlink of the first DC capacitor 3 reaches the first threshold voltage Vlink,th, the switching operation of the second power conversion circuit 4 is started, and The effective duty ratio of the power conversion circuit 4 is gradually increased from 0. This prevents the voltage link of the first DC capacitor 3 from becoming lower than the maximum value of the AC input voltage vac, and the first power conversion circuit 2 can stably continue normal operation.
　さらに、図４の例と同様に、第２の直流コンデンサ５の電圧Ｖｉｎｔが第２の閾値電圧Ｖｉｎｔ，ｔｈに達したときに第３の電力変換回路６のスイッチング動作が開始され、かつ第３の電力変換回路６の実効デューティ比が０から徐々に上昇される。それにより、第２の直流コンデンサ５の電圧Ｖｉｎｔが直流出力電圧Ｖｏｕｔより低くなることが防止され、第３の電力変換回路６が安定的に正常動作を継続することができる。 Further, similarly to the example of FIG. 4, when the voltage Vint of the second DC capacitor 5 reaches the second threshold voltage Vint,th, the switching operation of the third power conversion circuit 6 is started, and The effective duty ratio of the power conversion circuit 6 is gradually increased from 0. This prevents the voltage Vint of the second DC capacitor 5 from becoming lower than the DC output voltage Vout, and the third power conversion circuit 6 can stably continue normal operation.
　なお、負荷７として電圧源負荷７２が用いられる場合には、第２の電力変換回路４の動作開始のタイミングおよび第３の電力変換回路６の動作開始のタイミングを比較的柔軟に設定することができる。以下、その具体例を説明する。 When the voltage source load 72 is used as the load 7, the operation start timing of the second power conversion circuit 4 and the operation start timing of the third power conversion circuit 6 can be set relatively flexibly. it can. A specific example will be described below.
　図６は、負荷７に電圧源負荷７２が適用された場合における電力変換装置１００の初期動作の第２の例について説明するための図である。図６の例について、図５の例と異なる点を中心に説明する。 FIG. 6 is a diagram for explaining a second example of the initial operation of the power conversion device 100 when the voltage source load 72 is applied to the load 7. The example of FIG. 6 will be described focusing on the points different from the example of FIG.
　図６の例では、時刻ｔ３にて、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達しても、第２の電力変換回路４の動作は停止されたままである。その後の時刻ｔ４ｂにて、第３の電力変換回路６のスイッチング動作が開始され、電圧源負荷７２から第３の電力変換回路６を介して第２の直流コンデンサ５に電流が供給される。それにより、第２の直流コンデンサ５の充電が開始される。この場合、第２の電力変換回路４の実効デューティ比が０から徐々に増加されることにより、電圧Ｖｉｎｔが初期充電電圧Ｖｉｎｔ０から徐々に上昇する。 In the example of FIG. 6, even if the voltage Vlink of the first DC capacitor 3 reaches the first threshold voltage Vlink,th at time t3, the operation of the second power conversion circuit 4 remains stopped. At time t4b thereafter, the switching operation of the third power conversion circuit 6 is started, and current is supplied from the voltage source load 72 to the second DC capacitor 5 via the third power conversion circuit 6. As a result, the charging of the second DC capacitor 5 is started. In this case, the effective duty ratio of the second power conversion circuit 4 is gradually increased from 0, so that the voltage Vint gradually increases from the initial charging voltage Vint0.
　時刻ｔ３，ｔ４ｂでは、第２の電力変換回路４の動作が開始されていないので、第１の直流コンデンサ３と第２の直流コンデンサ５との間で電流は流れない。そのため、第１の電力変換回路２の動作は、第２の直流コンデンサ５の電圧Ｖｉｎｔに影響せず、第３の電力変換回路６の動作は、第１の直流コンデンサ３の電圧Ｖｌｉｎｋに影響しない。したがって、第１および第３の電力変換回路２，６のデューティ比を個別に調整することにより、第１および第２の直流コンデンサ３の電圧Ｖｌｉｎｋ，Ｖｉｎｔを個別に制御することができる。なお、第３の電力変換回路６の動作が開始される時刻は、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達する時刻と一致していてもよく、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達する前であってもよい。 At times t3 and t4b, the operation of the second power conversion circuit 4 has not started, so no current flows between the first DC capacitor 3 and the second DC capacitor 5. Therefore, the operation of the first power conversion circuit 2 does not affect the voltage Vint of the second DC capacitor 5, and the operation of the third power conversion circuit 6 does not affect the voltage Vlink of the first DC capacitor 3. .. Therefore, by individually adjusting the duty ratios of the first and third power conversion circuits 2 and 6, the voltages Vlink and Vint of the first and second DC capacitors 3 can be individually controlled. The time when the operation of the third power conversion circuit 6 is started may coincide with the time when the voltage Vlink of the first DC capacitor 3 reaches the first threshold voltage Vlink,th. It may be before the voltage Vlink of the DC capacitor 3 reaches the first threshold voltage Vlink,th.
　時刻５ｂにて、第２の直流コンデンサ５の電圧Ｖｉｎｔが第２の閾値電圧Ｖｉｎｔ，ｔｈに達する。この時刻５ｂにて、第１の電力変換回路２による力率制御が開始されるとともに、第２の電力変換回路４のスイッチング動作が開始される。これにより、電力変換装置１００から電圧源負荷７２に電流が流れ、電圧源負荷７２に電力が供給される。この場合、第２の電力変換回路４の実効デューティ比が０から徐々に増加されることにより、電圧源負荷７２に与えられる直流電流Ｉｏｕｔが０から徐々に上昇する。 At time 5b, the voltage Vint of the second DC capacitor 5 reaches the second threshold voltage Vint,th. At this time 5b, the power factor control by the first power conversion circuit 2 is started, and the switching operation of the second power conversion circuit 4 is started. As a result, current flows from the power conversion device 100 to the voltage source load 72, and power is supplied to the voltage source load 72. In this case, the effective duty ratio of the second power conversion circuit 4 is gradually increased from 0, so that the DC current Iout given to the voltage source load 72 is gradually increased from 0.
　直流出力電流Ｉｏｕｔが目標直流出力電流Ｉｏｕｔ＊に達した時刻ｔ６ｂにて、第１の電力変換回路２、第２の電力変換回路４、および第３の電力変換回路６のすべてが定常動作に移行する。 At time t6b when the DC output current Iout reaches the target DC output current Iout*, all of the first power conversion circuit 2, the second power conversion circuit 4, and the third power conversion circuit 6 shift to steady operation. To do.
　このように、負荷７として電圧源負荷７２が用いられる場合には、電圧源負荷７２からの電力により第２の直流コンデンサ５を充電することができる。また、第２の電力変換回路４の動作が開始されていないでは、第１の電力変換回路２の動作と第３の電力変換回路６の動作とが互いに影響しない。そのため、図６の例のように、第１の電力変換回路２の次に第３の電力変換回路６の動作を開始し、第３の電力変換回路６の次に第２の電力変換回路４の動作を開始することができる。 As described above, when the voltage source load 72 is used as the load 7, the second DC capacitor 5 can be charged with the electric power from the voltage source load 72. If the operation of the second power conversion circuit 4 is not started, the operation of the first power conversion circuit 2 and the operation of the third power conversion circuit 6 do not affect each other. Therefore, as in the example of FIG. 6, the operation of the third power conversion circuit 6 is started after the first power conversion circuit 2, and the operation of the third power conversion circuit 6 is followed by the second power conversion circuit 4. The operation of can be started.
　図７は、負荷７に電圧源負荷７２が適用された場合における電力変換装置１００の初期動作の第３の例について説明するための図である。図７の例について、図５の例と異なる点を中心に説明する。 FIG. 7 is a diagram for explaining a third example of the initial operation of the power conversion device 100 when the voltage source load 72 is applied to the load 7. The example of FIG. 7 will be described focusing on the points different from the example of FIG.
　図７の例では、時刻ｔ０において、電圧源負荷７２が第３の電力変換回路６の出力端子と電気的に接続されていない。そのため、時刻ｔ０では、電圧源負荷７２から第３の電力変換回路６の出力端子に電圧が印加されておらず、第２の直流コンデンサ５の電圧Ｖｉｎｔは０である。時刻ｔ１にて、交流入力電圧ｖａｃが第１の電力変換回路２の入力端子に印加された後、時刻ｔ２ｃにて、電圧源負荷７２が第３の電力変換回路６の出力端子と電気的に接続される。これにより、電圧源負荷７２の電圧が第３の電力変換回路６の出力端子に印加され、電圧Ｖｏｕｔとして検出される。このとき、第３の電力変換回路６のスイッチング素子の内蔵ダイオードもしくは外付けのダイオードを介して、第２の直流コンデンサ５が受動的に充電され、時刻ｔ３ｃにて、第２の直流コンデンサ５の電圧Ｖｉｎｔが初期充電電圧Ｖｉｎｔ０に達する。なお、時刻ｔ１において、交流入力電圧ｖａｃが第１の電力変換回路２の入力端子に印加されると同時に、電圧源負荷７２の電圧が第３の電力変換回路６の出力端子に印加されてもよい。 In the example of FIG. 7, the voltage source load 72 is not electrically connected to the output terminal of the third power conversion circuit 6 at time t0. Therefore, at time t0, no voltage is applied from the voltage source load 72 to the output terminal of the third power conversion circuit 6, and the voltage Vint of the second DC capacitor 5 is zero. After the AC input voltage vac is applied to the input terminal of the first power conversion circuit 2 at time t1, the voltage source load 72 is electrically connected to the output terminal of the third power conversion circuit 6 at time t2c. Connected. As a result, the voltage of the voltage source load 72 is applied to the output terminal of the third power conversion circuit 6 and detected as the voltage Vout. At this time, the second DC capacitor 5 is passively charged via the built-in diode of the switching element of the third power conversion circuit 6 or the external diode, and at time t3c, the second DC capacitor 5 is charged. The voltage Vint reaches the initial charging voltage Vint0. At time t1, even if the AC input voltage vac is applied to the input terminal of the first power conversion circuit 2 and the voltage of the voltage source load 72 is applied to the output terminal of the third power conversion circuit 6 at the same time. Good.
　時刻ｔ４ｃにて、第３の電力変換回路６のスイッチング動作が開始される。この場合、第３の電力変換回路６の実効デューティ比が徐々に上昇されることにより、第２の直流コンデンサ５の電圧Ｖｉｎｔが徐々に上昇する。時刻ｔ５ｃにて、第２の直流コンデンサ５の電圧Ｖｉｎｔが第２の閾値電圧Ｖｉｎｔ，ｔｈに達する。 At time t4c, the switching operation of the third power conversion circuit 6 is started. In this case, the effective duty ratio of the third power conversion circuit 6 is gradually increased, so that the voltage Vint of the second DC capacitor 5 is gradually increased. At time t5c, the voltage Vint of the second DC capacitor 5 reaches the second threshold voltage Vint,th.
　時刻ｔ６ｃにて、第１の電力変換回路２のスイッチング動作が開始される。この場合、第１の電力変換回路２の実効デューティ比が徐々に上昇されることにより、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが徐々に上昇する。時刻ｔ７ｃにて、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達すると、第１の電力変換回路２の力率制御が開始されるとともに、第２の電力変換回路４のスイッチング動作が開始される。これにより、電力変換装置１００から電圧源負荷７２に電流が流れ、電圧源負荷７２に電力が供給される。この場合、第２の電力変換回路４の実効デューティ比が０から徐々に増加されることにより、電圧源負荷７２に与えられる直流電流Ｉｏｕｔが０から徐々に上昇する。 At time t6c, the switching operation of the first power conversion circuit 2 is started. In this case, the effective duty ratio of the first power conversion circuit 2 is gradually increased, so that the voltage Vlink of the first DC capacitor 3 is gradually increased. At time t7c, when the voltage Vlink of the first DC capacitor 3 reaches the first threshold voltage Vlink,th, the power factor control of the first power conversion circuit 2 is started and the second power conversion circuit is started. The switching operation of No. 4 is started. As a result, current flows from the power conversion device 100 to the voltage source load 72, and power is supplied to the voltage source load 72. In this case, the effective duty ratio of the second power conversion circuit 4 is gradually increased from 0, so that the DC current Iout given to the voltage source load 72 is gradually increased from 0.
　直流出力電流Ｉｏｕｔが目標直流出力電流Ｉｏｕｔ＊まで達した時刻ｔ８ｃにて、第１の電力変換回路２、第２の電力変換回路４、および第３の電力変換回路６のすべてが定常動作に移行する。 At time t8c when the DC output current Iout reaches the target DC output current Iout*, all of the first power conversion circuit 2, the second power conversion circuit 4, and the third power conversion circuit 6 shift to the normal operation. To do.
　図６の例と同様に、負荷７として電圧源負荷７２が用いられる場合には、電圧源負荷７２からの電力により第２の直流コンデンサ５を充電することができる。また、第２の電力変換回路４の動作が開始されていない状態では、第１の電力変換回路２の動作と第３の電力変換回路６の動作とが互いに影響しない。そのため、図７の例のように、第１の電力変換回路２の次に第３の電力変換回路６の動作を開始し、第３の電力変換回路６の次に第２の電力変換回路４の動作を開始することができる。 Similarly to the example of FIG. 6, when the voltage source load 72 is used as the load 7, the second DC capacitor 5 can be charged by the electric power from the voltage source load 72. Further, in a state where the operation of the second power conversion circuit 4 is not started, the operation of the first power conversion circuit 2 and the operation of the third power conversion circuit 6 do not influence each other. Therefore, as in the example of FIG. 7, the operation of the third power conversion circuit 6 is started after the first power conversion circuit 2, and the operation of the second power conversion circuit 4 is started after the third power conversion circuit 6. The operation of can be started.
　なお、図６および図７の例では、第１の電力変換回路２と第３の電力変換回路６とが異なる時刻に動作を開始するが、第１の電力変換回路２と第３の電力変換回路６とが同時に動作を開始してもよい。 Note that in the examples of FIGS. 6 and 7, the first power conversion circuit 2 and the third power conversion circuit 6 start operating at different times, but the first power conversion circuit 2 and the third power conversion circuit The circuit 6 and the circuit 6 may start operating at the same time.
　以上のように、実施の形態１に係る電力変換装置１００においては、第１～第３の電力変換回路２，４，６の動作が段階的に開始されることにより、第１～第３の電力変換回路２，４，６の動作が同時に開始される場合と異なり、第１および第２の直流コンデンサ３，５の電圧を個別に制御することができる。それにより、第１および第２の直流コンデンサ３の電圧を安定的に上昇させることができる。その後、第１の直流コンデンサ３の電圧Ｖｌｉｎｋが第１の閾値電圧Ｖｌｉｎｋ，ｔｈに達しかつ第２の直流コンデンサ５の電圧Ｖｉｎｔが第２の閾値電圧Ｖｉｎｔ，ｔｈに達した状態で、第３の電力変換回路６の動作が開始されることにより、第１～第３の電力変換回路２，４，６内における過電流ならびに第１および第２の直流コンデンサ３，５の過電圧を発生させることなく、電力変換装置１００から負荷７への電力供給を安定的に開始させることができる。 As described above, in the power conversion device 100 according to the first embodiment, the operations of the first to third power conversion circuits 2, 4, and 6 are started stepwise, so that the first to third power conversion circuits are started. Unlike the case where the operations of the power conversion circuits 2, 4, 6 are started simultaneously, the voltages of the first and second DC capacitors 3, 5 can be individually controlled. Thereby, the voltage of the first and second DC capacitors 3 can be stably increased. After that, in a state where the voltage Vlink of the first DC capacitor 3 reaches the first threshold voltage Vlink,th and the voltage Vint of the second DC capacitor 5 reaches the second threshold voltage Vint,th, Since the operation of the power conversion circuit 6 is started, overcurrent in the first to third power conversion circuits 2, 4 and 6 and overvoltage of the first and second DC capacitors 3 and 5 are not generated. The power supply from the power converter 100 to the load 7 can be stably started.
　上記実施の形態１では、第１の電力変換回路２がＡＣ／ＤＣコンバータ２０のみにより構成され、第３の電力変換回路６がＤＣ／ＤＣコンバータ６０のみにより構成されるが、第１および第３の電力変換回路２，６の構成は、これに限定されない。図８は、実施の形態１に係る電力変換装置１００の変形例を示す図である。 In the first embodiment, the first power conversion circuit 2 is composed only of the AC/DC converter 20, and the third power conversion circuit 6 is composed only of the DC/DC converter 60. The configurations of the power conversion circuits 2 and 6 are not limited to this. FIG. 8: is a figure which shows the modification of the power converter device 100 which concerns on Embodiment 1. As shown in FIG.
　図８に示す電力変換装置１００は、第１の電力変換回路２に代えて第１の電力変換回路２Ａを備え、第３の電力変換回路６に代えて第３の電力変換回路６Ａを備える。第１の電力変換回路２Ａは、図２および図３のＡＣ／ＤＣコンバータ２０に加えて、降圧型のＤＣ／ＤＣコンバータ２００を含む。ＤＣ／ＤＣコンバータ２００は、コンデンサ２１１、スイッチング素子２１２，２１３およびリアクトル２１４を含む。この第１の電力変換回路２Ａにおいては、ＡＣ／ＤＣコンバータ２０により交流電圧が直流電圧に変換され、変換後の直流電圧がＤＣ／ＤＣコンバータにより降圧されて出力される。 The power conversion device 100 shown in FIG. 8 includes a first power conversion circuit 2A in place of the first power conversion circuit 2 and a third power conversion circuit 6A in place of the third power conversion circuit 6. The first power conversion circuit 2A includes a step-down DC/DC converter 200 in addition to the AC/DC converter 20 of FIGS. 2 and 3. DC/DC converter 200 includes a capacitor 211, switching elements 212 and 213, and a reactor 214. In the first power conversion circuit 2A, the AC/DC converter 20 converts an AC voltage into a DC voltage, and the converted DC voltage is stepped down by the DC/DC converter and output.
　一般的に、負荷７の要求電力が比較的大きい場合には、高調波歪みを抑制するために、昇圧型のコンバータ（本例では、ＡＣ／ＤＣコンバータ２０）によって力率制御が行われる。しかしながら、そのような昇圧型のコンバータが用いられると、第２の電力変換回路４の絶縁トランス４９に印加される電圧が大きくなり、鉄損が増加するという問題がある。そこで、図８の例では、ＤＣ／ＤＣコンバータ２００によって絶縁トランス４９への印加電圧を低減することができ、鉄損の増加を抑制することができる。 Generally, when the required power of the load 7 is relatively large, the power factor control is performed by the boost converter (AC/DC converter 20 in this example) in order to suppress harmonic distortion. However, when such a boost converter is used, there is a problem that the voltage applied to the insulating transformer 49 of the second power conversion circuit 4 increases and the iron loss increases. Therefore, in the example of FIG. 8, the DC/DC converter 200 can reduce the voltage applied to the insulating transformer 49, and can suppress an increase in iron loss.
　図８に示す第３の電力変換回路６Ａは、図２および図３のＤＣ／ＤＣコンバータ６０に加えて、絶縁型ＤＣ／ＤＣコンバータ６００を含む。絶縁型ＤＣ／ＤＣコンバータ６００は、絶縁トランス６１０、スイッチング素子６１１～６１８およびコンデンサ６１９を含む。この第３の電力変換回路６Ａにおいては、ＤＣ／ＤＣコンバータ６０により直流電圧が直流電圧に変換され、変換後の直流電圧が絶縁型ＤＣ／ＤＣコンバータ６０により変圧されて出力される。 The third power conversion circuit 6A shown in FIG. 8 includes an insulation type DC/DC converter 600 in addition to the DC/DC converter 60 of FIGS. 2 and 3. The insulation type DC/DC converter 600 includes an insulation transformer 610, switching elements 611 to 618, and a capacitor 619. In the third power conversion circuit 6A, the DC voltage is converted into the DC voltage by the DC/DC converter 60, and the converted DC voltage is transformed by the insulating DC/DC converter 60 and output.
　ＤＣ／ＤＣコンバータ２００のスイッチング素子２１２，２１３および絶縁型ＤＣ／ＤＣコンバータ６００のスイッチング素子６１１～６１８は、制御部８によりオンオフ制御される。この場合、ＡＣ／ＤＣコンバータ２０の動作とＤＣ／ＤＣコンバータ２００の動作とが同時に開始されてもよく、ＡＣ／ＤＣコンバータ２０の動作が開始されてから時間が経過した後にＤＣ／ＤＣコンバータ２００の動作が開始されてもよい。また、ＤＣ／ＤＣコンバータ６０の動作と絶縁型ＤＣ／ＤＣコンバータ６００の動作とが同時に開始されてもよく、ＤＣ／ＤＣコンバータ６０の動作が開始されてから時間が経過した後に絶縁型ＤＣ／ＤＣコンバータ６００の動作が開始されてもよい。また、負荷７として電圧源負荷７２が用いられる場合には、絶縁型ＤＣ／ＤＣコンバータ６００の動作が開始されてから時間が経過した後にＤＣ／ＤＣコンバータ６０の動作が開始されてもよい。 The switching elements 212 and 213 of the DC/DC converter 200 and the switching elements 611 to 618 of the insulation type DC/DC converter 600 are on/off controlled by the control unit 8. In this case, the operation of the AC/DC converter 20 and the operation of the DC/DC converter 200 may be started at the same time, and the operation of the DC/DC converter 200 may be started after a lapse of time after the operation of the AC/DC converter 20 is started. The operation may be started. Further, the operation of the DC/DC converter 60 and the operation of the insulation type DC/DC converter 600 may be started simultaneously, and the insulation type DC/DC may be started after a lapse of time from the start of the operation of the DC/DC converter 60. The operation of converter 600 may be started. When the voltage source load 72 is used as the load 7, the operation of the DC/DC converter 60 may be started after a lapse of time after the operation of the insulating DC/DC converter 600 is started.
　電力変換装置１００は、第１～３の電力変換回路２（２Ａ），４，６（６Ａ）に加えて、さらに他の電力変換回路を備えてもよい。図９は、実施の形態１に係る電力変換装置１００の他の変形例を示す図である。図９に示す電力変換装置１００においては、第１の電力変換回路２、第１の直流コンデンサ３および第２の電力変換回路４と並列に、第４の電力変換回路９１および第５の電力変換回路９２が接続される。 The power conversion device 100 may further include other power conversion circuits in addition to the first to third power conversion circuits 2 (2A), 4, 6 (6A). FIG. 9: is a figure which shows the other modification of the power converter device 100 which concerns on Embodiment 1. As shown in FIG. In the power conversion device 100 shown in FIG. 9, the fourth power conversion circuit 91 and the fifth power conversion circuit are arranged in parallel with the first power conversion circuit 2, the first DC capacitor 3, and the second power conversion circuit 4. The circuit 92 is connected.
　第４の電力変換回路９１は、スイッチング素子９１１～９１４、コンデンサ９１５、および非接触受電コイル９１６を含む。スイッチング素子９１１～９１４は、フルブリッジ型に接続される。スイッチング素子９１１と、スイッチング素子９１２と、が直列接続される接続点に非接触受電コイル９１６の一端が接続され、スイッチング素子９１３と、スイッチング素子９１４と、が直列接続される接続点に非接触受電コイル９１６の他端が接続される。第４の電力変換回路９１は、一対の第３の直流母線９１７を介して一対の第２の直流母線５１にそれぞれ接続される。 The fourth power conversion circuit 91 includes switching elements 911 to 914, a capacitor 915, and a non-contact power receiving coil 916. The switching elements 911 to 914 are connected in a full bridge type. One end of the non-contact power receiving coil 916 is connected to a connection point where the switching element 911 and the switching element 912 are connected in series, and non-contact power reception is performed at a connection point where the switching element 913 and the switching element 914 are connected in series. The other end of the coil 916 is connected. The fourth power conversion circuit 91 is connected to the pair of second DC buses 51 via the pair of third DC buses 917, respectively.
　第５の電力変換回路９２は、スイッチング素子９２１～９２８、直流リンクコンデンサ９２９、交流リアクトル９３１，９３２、および非接触送電コイル９３３を含む。スイッチング素子９２１～９２４およびスイッチング素子９２５～９２８は、それぞれフルブリッジ型に接続されている。交流リアクトル９３１，９３２の一端は、交流電源１１と接続されている。交流リアクトル９３１の他端は、直列接続されたスイッチング素子９２１とスイッチング素子９２２との接続点に接続され、交流リアクトル９３２の他端は、直列接続されたスイッチング素子９２３とスイッチング素子９２４との接続点に接続されている。直流リンクコンデンサ９２９は、スイッチング素子９２１～９２４とスイッチング素子９２５～９２８とを接続する直流母線の正極および負極に接続されている。直列接続されたスイッチング素子９２５とスイッチング素子９２６との接続点に非接触送電コイル９３３の一端が接続され、直列接続されたスイッチング素子９２７とスイッチング素子９２８との接続点に非接触送電コイル９３３の他端が接続される。 The fifth power conversion circuit 92 includes switching elements 921 to 928, a DC link capacitor 929, AC reactors 931 and 932, and a non-contact power transmission coil 933. The switching elements 921 to 924 and the switching elements 925 to 928 are connected in a full bridge type. One ends of the AC reactors 931 and 932 are connected to the AC power supply 11. The other end of AC reactor 931 is connected to a connection point between switching element 921 and switching element 922 that are connected in series, and the other end of AC reactor 932 is a connection point between switching element 923 and switching element 924 that are connected in series. It is connected to the. The DC link capacitor 929 is connected to the positive and negative electrodes of the DC bus connecting the switching elements 921 to 924 and the switching elements 925 to 928. One end of the non-contact power transmission coil 933 is connected to a connection point between the switching element 925 and the switching element 926 connected in series, and the non-contact power transmission coil 933 is connected to a connection point between the switching element 927 and the switching element 928 connected in series. The ends are connected.
　第４の電力変換回路９１の非接触受電コイル９１６と第５の電力変換回路９２の非接触送電コイル９３３とが磁気的に結合されることにより、第５の電力変換回路９２から第４の電力変換回路９１に非接触で電力が伝送される。第４の電力変換回路９１から第３の直流母線９１７を介して第２の直流コンデンサ５に直流電圧が与えられる。 The non-contact power reception coil 916 of the fourth power conversion circuit 91 and the non-contact power transmission coil 933 of the fifth power conversion circuit 92 are magnetically coupled to each other, so that the fifth power conversion circuit 92 outputs the fourth power. Electric power is transmitted to the conversion circuit 91 in a contactless manner. A DC voltage is applied from the fourth power conversion circuit 91 to the second DC capacitor 5 via the third DC bus 917.
　＜実施の形態２＞
　本発明の実施の形態２に係る電力変換装置について、上記実施形態１に係る電力変換装置１００と異なる点を中心に説明する。実施の形態２に係る電力変換装置の構成は、実施の形態１に示す場合と概ね同様であるため、構成の詳細な説明は繰り返さない。 <Second Embodiment>
A power conversion device according to Embodiment 2 of the present invention will be described focusing on differences from the power conversion device 100 according to Embodiment 1 above. The configuration of the power conversion device according to the second embodiment is substantially the same as the case shown in the first embodiment, and therefore detailed description of the configuration will not be repeated.
　図１０は、実施の形態２に係る電力変換装置１００の具体的な回路構成例を示す図である。実施の形態２に係る電力変換装置１００は、第１の電力変換回路２に代えて第１の電力変換回路２Ｂを備え、第３の電力変換回路６に代えて第３の電力変換回路６Ｂを備える。 FIG. 10 is a diagram showing a specific circuit configuration example of the power conversion device 100 according to the second embodiment. The power conversion device 100 according to the second embodiment includes a first power conversion circuit 2B in place of the first power conversion circuit 2 and a third power conversion circuit 6B in place of the third power conversion circuit 6. Prepare
　第１の電力変換回路２Ｂは、スイッチング素子２２１、２２２および平滑用直流リアクトル２２３からなるＤＣ／ＤＣコンバータ２０Ｂを含む。ＤＣ／ＤＣコンバータ２０Ｂは、降圧チョッパの回路構成を有する。第１の電力変換回路２Ｂの入力端子には、入力電源１として直流電源１２が接続される。なお、図１０に示すＤＣ／ＤＣコンバータ２０Ｂは、降圧チョッパの回路構成を有するが、昇圧型や昇降圧型の回路構成を有してもよく、また、インターリーブの構成や並列接続構成を有してもよいことは言うまでもない。 The first power conversion circuit 2B includes a DC/DC converter 20B including switching elements 221, 222 and a smoothing DC reactor 223. The DC/DC converter 20B has a circuit configuration of a step-down chopper. The DC power supply 12 as the input power supply 1 is connected to the input terminal of the first power conversion circuit 2B. Although the DC/DC converter 20B shown in FIG. 10 has a step-down chopper circuit configuration, it may have a step-up type or step-up/down type circuit configuration, and also has an interleave configuration or a parallel connection configuration. It goes without saying that it is good.
　第３の電力変換回路６Ｂは、スイッチング素子６２１～６２４および交流リアクトル６２５、６２６からなり、直流電圧を交流電圧に変換するインバータ６０Ｂを含む。スイッチング素子６２１～６２４はフルブリッジ型に接続されている。交流リアクトル６２５の一端はスイッチング素子６２１とスイッチング素子６２２との接続点に接続されている。交流リアクトル６２６の一端はスイッチング素子６２３とスイッチング素子６２４との接続点に接続されている。交流リアクトル６２５，６２６の他端に、負荷７として抵抗負荷７１が接続されている。 The third power conversion circuit 6B includes switching elements 621 to 624 and AC reactors 625 and 626, and includes an inverter 60B that converts a DC voltage into an AC voltage. The switching elements 621 to 624 are connected in a full bridge type. One end of the AC reactor 625 is connected to a connection point between the switching element 621 and the switching element 622. One end of the AC reactor 626 is connected to a connection point between the switching element 623 and the switching element 624. A resistive load 71 is connected as the load 7 to the other ends of the AC reactors 625 and 626.
　なお、図１０に示す第３の電力変換回路６では、交流リアクトル６２５，６２６が交流電源の両極側にそれぞれ接続されるが、片極側のみに接続されもよい。すなわち、交流リアクトル６２５，６２６のいずれか一方のみが用いられてもよい。 Note that, in the third power conversion circuit 6 shown in FIG. 10, the AC reactors 625 and 626 are connected to both sides of the AC power supply, but may be connected to only one side. That is, only one of AC reactors 625 and 626 may be used.
　図１０に示す第１の電力変換回路２ＢのＤＣ／ＤＣコンバータ２０Ｂは、図２および図３に示す第３の電力変換回路６のＤＣ／ＤＣコンバータ６０と入出力が逆の構成を有し、図１０に示す第３の電力変換回路６Ｂのインバータ６０Ｂは、図２および図３に示す第１の電力変換回路２のＡＣ／ＤＣコンバータ２０と入出力が逆の構成を有する。そのため、実施の形態１における電力の伝送方向を正方向と定義し、その反対の方向を逆方向と定義した場合、実施の形態２に係る電力変換装置１００は、逆方向に電力を伝送する。なお、電力変換装置１００が双方向に電力を伝送可能に構成されている場合、共通の電力変換装置１００により実施の形態１と実施の形態２の両方を実現することが可能である。 The DC/DC converter 20B of the first power conversion circuit 2B shown in FIG. 10 has a configuration in which the input/output is opposite to that of the DC/DC converter 60 of the third power conversion circuit 6 shown in FIGS. 2 and 3. The inverter 60B of the third power conversion circuit 6B shown in FIG. 10 has a configuration in which the input and output are opposite to those of the AC/DC converter 20 of the first power conversion circuit 2 shown in FIGS. 2 and 3. Therefore, when the power transmission direction in the first embodiment is defined as the forward direction and the opposite direction is defined as the reverse direction, the power conversion device 100 according to the second embodiment transmits the power in the reverse direction. When the power conversion device 100 is configured to be capable of bidirectionally transmitting power, it is possible to realize both the first embodiment and the second embodiment by the common power conversion device 100.
　電流検出器Ｄ１は、直流電源１２から第１の電力変換回路２Ｂに流れる直流入力電流Ｉｄｃを検出する。電流検出器Ｄ２は、第３の電力変換回路６Ｂから抵抗負荷７１に流れる交流出力電流ｉｏｕｔを検出する。電圧検出器Ｄ３は、直流電源１２から第１の電力変換回路２に与えられる直流入力電圧Ｖｄｃを検出する。電圧検出器Ｄ４は、第１の直流コンデンサ３の電圧Ｖｉｎｔを検出する。電圧検出器Ｄ５は、第２の直流コンデンサ５の電圧Ｖｌｉｎｋを検出する。電圧検出器Ｄ６は、第３の電力変換回路６から抵抗負荷７１に与えられる交流出力電圧ｖｏｕｔを検出する。制御部８は、検出器Ｄ１～Ｄ６から与えられた検出値の一部または全部に基づいてフィードバック演算を行い、各スイッチング素子のオンオフを制御する。 The current detector D1 detects the DC input current Idc flowing from the DC power supply 12 to the first power conversion circuit 2B. The current detector D2 detects the AC output current iout flowing from the third power conversion circuit 6B to the resistance load 71. The voltage detector D3 detects the DC input voltage Vdc supplied from the DC power supply 12 to the first power conversion circuit 2. The voltage detector D4 detects the voltage Vint of the first DC capacitor 3. The voltage detector D5 detects the voltage Vlink of the second DC capacitor 5. The voltage detector D6 detects the AC output voltage vout given to the resistive load 71 from the third power conversion circuit 6. The control unit 8 performs feedback calculation based on a part or all of the detection values given from the detectors D1 to D6, and controls on/off of each switching element.
　定常時における制御部８の役割について、上記実施の形態１と異なる主な点は、次の点である。制御部８は、予め定められた目標直流電圧Ｖｉｎｔ＊と第１の直流コンデンサ３の直流電圧Ｖｉｎｔの検出値との電圧差を算出し、算出した電圧差をフィードバック量として比例制御または比例積分制御により出力値を演算する。 Regarding the role of the control unit 8 in the steady state, the main points different from those in the first embodiment are as follows. The control unit 8 calculates a voltage difference between a predetermined target DC voltage Vint* and a detected value of the DC voltage Vint of the first DC capacitor 3, and uses the calculated voltage difference as a feedback amount for proportional control or proportional-integral control. The output value is calculated by.
　また、制御部８は、予め定められた目標直流電圧Ｖｌｉｎｋ＊と第２の直流コンデンサ５の直流電圧Ｖｌｉｎｋの検出値との電圧差を算出し、算出した電圧差をフィードバック量として比例制御または比例積分制御により出力値を演算する。 Further, the control unit 8 calculates a voltage difference between a predetermined target DC voltage Vlink* and a detected value of the DC voltage Vlink of the second DC capacitor 5, and performs proportional control or proportional control using the calculated voltage difference as a feedback amount. Output value is calculated by integral control.
　また、制御部８は、抵抗負荷７１への出力電圧が正弦波交流になるように予め定められた目標交流出力電圧の実効値Ｖｏｕｔ，ｒｍｓ＊に振幅が√２の正弦波電圧を乗じた目標交流出力電圧ｖｏｕｔ＊と交流出力電圧ｖｏｕｔとの電圧差を算出し、算出した電圧差をフィードバック量として比例制御もしくは比例積分制御により出力を演算する。 Further, the control unit 8 sets a target obtained by multiplying the effective value Vout, rms* of the target AC output voltage, which is predetermined so that the output voltage to the resistive load 71 is a sine wave AC, by the sine wave voltage having an amplitude of √2. The voltage difference between the AC output voltage vout* and the AC output voltage vout is calculated, and the calculated voltage difference is used as a feedback amount to calculate the output by proportional control or proportional integral control.
　各出力値に基づいて、第１の直流コンデンサ３の電圧Ｖｉｎｔが目標直流電圧Ｖｉｎｔ＊に追従するように制御され、第２の直流コンデンサ５の電圧Ｖｌｉｎｋが目標直流電圧Ｖｌｉｎｋ＊に追従するように制御され、交流出力電圧ｖｏｕｔが目標交流出力電圧ｖｏｕｔ＊に追従するように制御される。 Based on each output value, the voltage Vint of the first DC capacitor 3 is controlled so as to follow the target DC voltage Vint*, and the voltage Vlink of the second DC capacitor 5 follows the target DC voltage Vlink*. It is controlled so that the AC output voltage vout follows the target AC output voltage vout*.
　次に、実施の形態２における初期動作時の制御部８の役割について、上記実施の形態１における初期動作時の制御部８の役割と異なる点を中心に説明する。図１１は、実施の形態２における初期動作について説明するための図である。図１１には、直流入力電圧Ｖｄｃ、第１の直流コンデンサ３の電圧Ｖｉｎｔ，第２の直流コンデンサ５の電圧Ｖｌｉｎｋおよび交流出力電圧ｖｏｕｔの検出値が示される。 Next, the role of the control unit 8 at the time of the initial operation in the second embodiment will be described focusing on the points different from the role of the control unit 8 at the time of the initial operation in the first embodiment. FIG. 11 is a diagram for explaining the initial operation in the second embodiment. FIG. 11 shows the detected values of the DC input voltage Vdc, the voltage Vint of the first DC capacitor 3, the voltage Vlink of the second DC capacitor 5, and the AC output voltage vout.
　図１１の例においては、時刻ｔ０にて、第１の電力変換回路２Ｂ、第２の電力変換回路４および第３の電力変換回路６Ｂのスイッチング動作はいずれも停止されている。また、時刻ｔ０にて、第１の直流コンデンサ３の電圧Ｖｉｎｔおよび第２の直流コンデンサ５の電圧Ｖｌｉｎｋはそれぞれ０である。 In the example of FIG. 11, at time t0, the switching operations of the first power conversion circuit 2B, the second power conversion circuit 4 and the third power conversion circuit 6B are all stopped. At time t0, the voltage Vint of the first DC capacitor 3 and the voltage Vlink of the second DC capacitor 5 are 0, respectively.
　制御部８は、検出器Ｄ１～Ｄ６による検出結果に基づいて、第１の直流コンデンサ３の電圧Ｖｉｎｔ、第２の直流コンデンサ５の電圧Ｖｌｉｎｋおよび交流出力電圧ｖｏｕｔが以下のように変化するように、第１～第３の電力変換回路２Ｂ，４，６Ｂを制御する。 The control unit 8 controls the voltage Vint of the first DC capacitor 3, the voltage Vlink of the second DC capacitor 5, and the AC output voltage vout to change as follows based on the detection results of the detectors D1 to D6. , And controls the first to third power conversion circuits 2B, 4, 6B.
　時刻ｔ１ｄにて、直流入力電圧Ｖｄｃが第１の電力変換回路２Ｂの入力端子に印加される。このとき、第１の電力変換回路２Ｂの各スイッチング素子の内蔵ダイオードまたは外付けのダイオードを介して第１の直流コンデンサ３が受動的に充電される。それにより、時刻ｔ２ｄにて、第１の直流コンデンサ３の電圧Ｖｉｎｔが初期充電電圧Ｖｉｎｔ０に上昇する。なお、第１の直流コンデンサ３の電圧Ｖｉｎｔが瞬時に充電されることによって時刻ｔ１ｄと時刻ｔ２ｄがほぼ一致していてもよい。 At time t1d, the DC input voltage Vdc is applied to the input terminal of the first power conversion circuit 2B. At this time, the first DC capacitor 3 is passively charged via the built-in diode or the external diode of each switching element of the first power conversion circuit 2B. As a result, at time t2d, the voltage Vint of the first DC capacitor 3 rises to the initial charging voltage Vint0. It should be noted that time t1d and time t2d may substantially coincide with each other by instantaneously charging the voltage Vint of the first DC capacitor 3.
　時刻ｔ３ｄにて、第１の電力変換回路２Ｂのスイッチング動作が開始される。この場合、第１の電力変換回路２Ｂの実効デューティ比が徐々に上昇されることにより、第１の直流コンデンサ３の電圧Ｖｉｎｔが徐々に上昇する。 At time t3d, the switching operation of the first power conversion circuit 2B is started. In this case, the effective duty ratio of the first power conversion circuit 2B is gradually increased, so that the voltage Vint of the first DC capacitor 3 is gradually increased.
　時刻ｔ４ｄにて、第１の直流コンデンサ３の電圧Ｖｉｎｔが予め定められた第１の閾値電圧Ｖｉｎｔ，ｔｈに達する。このとき、第２の電力変換回路４のスイッチング動作が開始される。これにより、第１の直流コンデンサ３から第２の電力変換回路４を介して第２の直流コンデンサ５に電流が流れ、第２の直流コンデンサ５の充電が開始される。 At time t4d, the voltage Vint of the first DC capacitor 3 reaches the predetermined first threshold voltage Vint,th. At this time, the switching operation of the second power conversion circuit 4 is started. As a result, current flows from the first DC capacitor 3 to the second DC capacitor 5 via the second power conversion circuit 4, and charging of the second DC capacitor 5 is started.
　第１の閾値電圧Ｖｉｎｔ，ｔｈは、式（４）の条件を満たす。
Figure JPOXMLDOC01-appb-I000004
The first threshold voltage Vint,th satisfies the condition of Expression (4).
Figure JPOXMLDOC01-appb-I000004
　ここで、第１の電力変換回路２Ｂの動作中に、第１の直流コンデンサ３の電圧Ｖｉｎｔが直流入力電圧Ｖｄｃより低くなると、第１の電力変換回路２Ｂが正常動作（昇圧動作）を継続することができなくなる。具体的には、スイッチング素子２１～２４のオンオフに関係なく、直流電源１２と第１の直流コンデンサ３との間の電流経路が固定される。そのため、第１の直流コンデンサ３の電圧Ｖｉｎｔは、直流入力電圧Ｖｄｃよりも高く維持される必要がある。 Here, when the voltage Vint of the first DC capacitor 3 becomes lower than the DC input voltage Vdc during the operation of the first power conversion circuit 2B, the first power conversion circuit 2B continues the normal operation (boosting operation). Can't do it. Specifically, the current path between the DC power supply 12 and the first DC capacitor 3 is fixed regardless of whether the switching elements 21 to 24 are turned on or off. Therefore, the voltage Vint of the first DC capacitor 3 needs to be maintained higher than the DC input voltage Vdc.
　本実施の形態では、第１の電力変換回路２Ｂによって第１の直流コンデンサ３の電圧Ｖｉｎｔが第１の閾値電圧Ｖｉｎｔ，ｔｈまで上昇されてから第２の電力変換回路４のスイッチング動作が開始される。これにより、第１の直流コンデンサ３の電圧Ｖｉｎｔと直流入力電圧Ｖｄｃとの間に一定のマージン（余裕）を確保した状態で、第２の電力変換回路４のスイッチング動作を開始させることができる。また、本実施の形態では、第２の電力変換回路４の実効デューティ比は０から徐々に増加され、第１の直流コンデンサ３から第２の直流コンデンサ５に流れる電流は０から徐々に増加する。それにより、第２の電力変換回路４の動作開始に伴う第１の直流コンデンサ３の電圧Ｖｉｎｔの急峻な低下が抑制される。 In the present embodiment, the switching operation of the second power conversion circuit 4 is started after the voltage Vint of the first DC capacitor 3 is raised to the first threshold voltage Vint,th by the first power conversion circuit 2B. It As a result, the switching operation of the second power conversion circuit 4 can be started in a state in which a certain margin is provided between the voltage Vint of the first DC capacitor 3 and the DC input voltage Vdc. Further, in the present embodiment, the effective duty ratio of the second power conversion circuit 4 is gradually increased from 0, and the current flowing from the first DC capacitor 3 to the second DC capacitor 5 is gradually increased from 0. .. As a result, a sharp drop in the voltage Vint of the first DC capacitor 3 due to the start of operation of the second power conversion circuit 4 is suppressed.
　これらにより、第１の直流コンデンサ３の電圧Ｖｉｎｔが直流入力電圧Ｖｄｃより低くなることが防止され、第１の電力変換回路２が安定的に正常動作を継続することができる。 With these, the voltage Vint of the first DC capacitor 3 is prevented from becoming lower than the DC input voltage Vdc, and the first power conversion circuit 2 can stably continue normal operation.
　また、第１の閾値電圧Ｖｉｎｔ，ｔｈが目標直流電圧Ｖｉｎｔ＊より小さい値に設定されているため、第１の直流コンデンサ３の電圧Ｖｉｎｔが過電圧となることが防止されるとともに、第２の電力変換回路４の動作開始までの時間を短くすることができる。 Moreover, since the first threshold voltage Vint,th is set to a value smaller than the target DC voltage Vint*, the voltage Vint of the first DC capacitor 3 is prevented from becoming an overvoltage, and the second power The time until the operation of the conversion circuit 4 starts can be shortened.
　その後、第１の直流コンデンサの電圧Ｖｉｎｔは、目標直流電圧Ｖｉｎｔ＊に追従するように制御される。 After that, the voltage Vint of the first DC capacitor is controlled so as to follow the target DC voltage Vint*.
　時刻ｔ５ｄにて、第２の直流コンデンサ５の電圧Ｖｌｉｎｋが、予め定められた第２の閾値電圧Ｖｌｉｎｋ，ｔｈに達すると、第１の電力変換回路２Ｂおよび第２の電力変換回路４に加えて、第３の電力変換回路６Ｂのスイッチング動作が開始される。この場合、第３の電力変換回路６Ｂの実効デューティ比は０から徐々に増加され、かつ抵抗負荷７１への交流出力電圧ｖｏｕｔが、目標交流出力電圧ｖｏｕｔ＊へと追従するように、第３の電力変換回路６Ｂが制御される。それにより、第２の直流コンデンサ５から抵抗負荷７１に流れる交流出力電圧ｖｏｕｔの実効値は、０から徐々に増加される。 At time t5d, when the voltage Vlink of the second DC capacitor 5 reaches the predetermined second threshold voltage Vlink,th, in addition to the first power conversion circuit 2B and the second power conversion circuit 4, The switching operation of the third power conversion circuit 6B is started. In this case, the effective duty ratio of the third power conversion circuit 6B is gradually increased from 0, and the AC output voltage vout to the resistance load 71 follows the target AC output voltage vout*. The power conversion circuit 6B is controlled. As a result, the effective value of the AC output voltage vout flowing from the second DC capacitor 5 to the resistance load 71 is gradually increased from 0.
　第２の閾値電圧Ｖｌｉｎｋ，ｔｈは、式（５）の条件を満たす。なお、式（５）における「√２Ｖｏｕｔ＊，ｒｍｓ」は、目標交流出力電圧ｖｏｕｔ＊の最大値に相当する。
Figure JPOXMLDOC01-appb-I000005
The second threshold voltage Vlink,th satisfies the condition of Expression (5). Note that “√2Vout*,rms” in the equation (5) corresponds to the maximum value of the target AC output voltage vout*.
Figure JPOXMLDOC01-appb-I000005
　これにより、第２の直流コンデンサ５の電圧Ｖｌｉｎｋが目標交流出力電圧ｖｏｕｔ＊の最大値より低くなることが防止される。その結果、第２の直流コンデンサ５が安定的に正常動作を継続することができる。 This prevents the voltage Vlink of the second DC capacitor 5 from becoming lower than the maximum value of the target AC output voltage vout*. As a result, the second DC capacitor 5 can stably continue normal operation.
　その後、第２の直流コンデンサの電圧Ｖｌｉｎｋは、目標直流電圧Ｖｌｉｎｋ＊に追従するように制御される。 After that, the voltage Vlink of the second DC capacitor is controlled so as to follow the target DC voltage Vlink*.
　時刻ｔ６ｄにて、交流出力電圧ｖｏｕｔが目標交流出力電圧の実効値Ｖｏｕｔ，ｒｍｓ＊に振幅が√２の正弦波電圧を乗じた目標交流出力電圧ｖｏｕｔ＊まで達すると、第１の電力変換回路２Ｂ、第２の電力変換回路４および第３の電力変換回路６Ｂの全てが上記の定常動作に移行する。 At time t6d, when the AC output voltage vout reaches the target AC output voltage vout* obtained by multiplying the effective value Vout, rms* of the target AC output voltage by the sine wave voltage having the amplitude of √2, the first power conversion circuit 2B. , The second power conversion circuit 4 and the third power conversion circuit 6B all shift to the above-described steady operation.
　このように、実施の形態２においても、第１～第３の電力変換回路２Ｂ，４，６Ｂの動作が段階的に開始されることにより、第１～第３の電力変換回路２Ｂ，４，６Ｂの動作が同時に開始される場合と異なり、第１および第２の直流コンデンサ３，５の電圧を個別に制御することができる。それにより、第１および第２の直流コンデンサ３，５の電圧を安定的に上昇させることができる。その後、第１の直流コンデンサ３の電圧Ｖｉｎｔが第１の閾値電圧Ｖｉｎｔ，ｔｈに達しかつ第２の直流コンデンサ５の電圧Ｖｌｉｎｋが第２の閾値電圧Ｖｌｉｎｋ，ｔｈに達した状態で、第３の電力変換回路６の動作が開始されることにより、第１～第３の電力変換回路２Ｂ，４，６Ｂ内における過電流ならびに第１および第２の直流コンデンサ３，５の過電圧を発生させることなく、電力変換装置１００から負荷７への電力供給を安定的に開始させることができる。 As described above, also in the second embodiment, the operations of the first to third power conversion circuits 2B, 4, 6B are started stepwise, whereby the first to third power conversion circuits 2B, 4, 4 are started. Unlike the case where the operations of 6B are simultaneously started, the voltages of the first and second DC capacitors 3 and 5 can be individually controlled. Thereby, the voltage of the first and second DC capacitors 3 and 5 can be stably increased. After that, in a state where the voltage Vint of the first DC capacitor 3 reaches the first threshold voltage Vint,th and the voltage Vlink of the second DC capacitor 5 reaches the second threshold voltage Vlink,th, By starting the operation of the power conversion circuit 6, without generating an overcurrent in the first to third power conversion circuits 2B, 4, 6B and an overvoltage of the first and second DC capacitors 3, 5. The power supply from the power converter 100 to the load 7 can be stably started.
　なお、実施の形態２においても、実施の形態１と同様に種々の変更が可能である。例えば、図３の例と同様に、負荷７として電圧源負荷７２が用いられてもよく、図８の例と同様に、第１の電力変換回路２Ｂおよび第３の電力変換回路６Ｂに他の回路が追加されてもよく、図９の例と同様に、第１～第３の電力変換回路２Ｂ，４，６Ｂにさらに他の電力変換回路が接続されてもよい。 Incidentally, also in the second embodiment, various changes can be made as in the first embodiment. For example, as in the example of FIG. 3, the voltage source load 72 may be used as the load 7, and similarly to the example of FIG. 8, the first power conversion circuit 2B and the third power conversion circuit 6B may be different from each other. A circuit may be added, and as in the example of FIG. 9, another power conversion circuit may be connected to the first to third power conversion circuits 2B, 4, 6B.
　制御部８の機能は、電子回路などのハードウェアで実現されてもよく、ソフトウェアで実現されてもよい。図１２は、制御部８の少なくとも一部の機能がソフトウェアで実現される例を示す図である。図１２の例では、制御部８が、処理装置（プロセッサ）５０１および記憶装置（メモリ）５０２を備える。処理装置５０１は、例えばＣＰＵ（中央演算処理装置）であり、記憶装置５０２に記憶されたプログラムを読み出して実行することにより、上記実施の形態における制御部８の少なくとも一部の機能を実現することができる。 The function of the control unit 8 may be realized by hardware such as an electronic circuit or software. FIG. 12 is a diagram illustrating an example in which at least a part of the functions of the control unit 8 is realized by software. In the example of FIG. 12, the control unit 8 includes a processing device (processor) 501 and a storage device (memory) 502. The processing device 501 is, for example, a CPU (central processing unit), and realizes at least a part of the functions of the control unit 8 in the above-described embodiment by reading and executing a program stored in the storage device 502. You can
　１　入力電源
　２，２Ａ，２Ｂ　第１の電力変換回路
　３　第１の直流コンデンサ
　４　第２の電力変換回路
　５　第２の直流コンデンサ
　６，６Ａ，６Ｂ　第３の電力変換回路
　７　負荷
　８　制御部
　２０　ＡＣ／ＤＣコンバータ
　３１　第１の直流母線
　４０，６００　絶縁型ＤＣ／ＤＣコンバータ
　５１　第２の直流母線
　６０，２００，２０Ｂ　ＤＣ／ＤＣコンバータ
　６０Ｂ　インバータ
　７１　抵抗負荷
　７２　電圧源負荷
　９１　第４の電力変換回路
　９２　第５の電力変換回路
　１００　電力変換装置 1 Input Power Source 2, 2A, 2B First Power Conversion Circuit 3 First DC Capacitor 4 Second Power Conversion Circuit 5 Second DC Capacitor 6, 6A, 6B Third Power Conversion Circuit 7 Load 8 Controller 20 AC/DC converter 31 First direct current bus 40,600 Insulation type DC/DC converter 51 Second direct current bus 60,200,20B DC/DC converter 60B Inverter 71 Resistive load 72 Voltage source load 91 Fourth power conversion circuit 92 fifth power converter circuit 100 power converter

Claims (13)

  1. 　入力電源からの電圧を直流電圧に変換し、変換後の直流電圧を出力する第１の電力変換回路と、
    　第１の直流母線を介して前記第１の電力変換回路に接続され、前記第１の電力変換回路から出力された直流電圧を変圧し、変圧後の直流電圧を出力する第２の電力変換回路と、
    　第２の直流母線を介して前記第２の電力変換回路に接続され、前記第２の電力変換回路から出力された直流電圧を変換し、変換後の直流電圧を負荷に出力する第３の電力変換回路と、
    　前記第１の直流母線に接続された第１の直流コンデンサと、
    　前記第２の直流母線に接続された第２の直流コンデンサと、
    　前記第１、第２および第３の電力変換回路が段階的に動作を開始し、前記第１の直流コンデンサの電圧が第１の閾値電圧に達しかつ前記第２の直流コンデンサの電圧が第２の閾値電圧に達した後に、前記第３の電力変換回路から前記負荷に電力が出力されるように、前記第１、第２および第３の電力変換回路を制御する制御部と、を備える、電力変換装置。     A first power conversion circuit that converts a voltage from an input power source into a DC voltage and outputs the converted DC voltage;
    A second power conversion circuit that is connected to the first power conversion circuit via a first DC bus, transforms the DC voltage output from the first power conversion circuit, and outputs the transformed DC voltage. When,
    Third power connected to the second power conversion circuit via a second DC bus, converting the DC voltage output from the second power conversion circuit, and outputting the converted DC voltage to a load. A conversion circuit,
    A first DC capacitor connected to the first DC bus,
    A second DC capacitor connected to the second DC bus,
    The first, second, and third power conversion circuits start operating stepwise, the voltage of the first DC capacitor reaches the first threshold voltage, and the voltage of the second DC capacitor is changed to the second voltage. A control unit that controls the first, second, and third power conversion circuits so that electric power is output from the third power conversion circuit to the load after the threshold voltage is reached. Power converter.
  2. 　前記制御部は、
    　前記入力電源から前記第１の電力変換回路に電圧が与えられた状態で前記第１、第２および第３の電力変換回路が順に動作を開始することによって前記第１および第２の直流コンデンサが順に充電されるように、前記第１、第２および第３の電力変換回路を制御する、請求項１に記載の電力変換装置。     The control unit is
    The first, second, and third power conversion circuits sequentially start operating in a state in which a voltage is applied to the first power conversion circuit from the input power source, whereby the first and second DC capacitors are The power conversion device according to claim 1, wherein the first, second, and third power conversion circuits are controlled so as to be sequentially charged.
  3. 　前記制御部は、
    　前記第１の直流コンデンサの電圧が前記第１の閾値電圧に達すると、前記第２の電力変換回路の動作を開始させる、請求項２に記載の電力変換装置。     The control unit is
    The power conversion device according to claim 2, wherein when the voltage of the first DC capacitor reaches the first threshold voltage, the operation of the second power conversion circuit is started.
  4. 　前記制御部は、前記第２の電力変換回路の動作開始時に前記第２の電力変換回路のデューティ比を徐々に上昇させる、請求項２または３に記載の電力変換装置。 The power conversion device according to claim 2 or 3, wherein the control unit gradually increases the duty ratio of the second power conversion circuit when the operation of the second power conversion circuit is started.
  5. 　前記制御部は、
    　前記第２の直流コンデンサの電圧が前記第２の閾値電圧に達すると、前記第３の電力変換回路の動作を開始させる、請求項２～４のいずれか一項に記載の電力変換装置。     The control unit is
    The power conversion device according to any one of claims 2 to 4, wherein when the voltage of the second DC capacitor reaches the second threshold voltage, the operation of the third power conversion circuit is started.
  6. 　前記制御部は、前記第３の電力変換回路の動作開始時に前記第２の電力変換回路のデューティ比を徐々に上昇させる、請求項２～５のいずれか一項に記載の電力変換装置。 The power conversion device according to any one of claims 2 to 5, wherein the control unit gradually increases the duty ratio of the second power conversion circuit when the operation of the third power conversion circuit is started.
  7. 　前記負荷は、自発的に電圧を発生する電圧源負荷であり、
    　前記制御部は、
    　前記入力電源から前記第１の電力変換回路に電圧が与えられた状態で前記第１の電力変換回路が動作を開始し、前記電圧源負荷から前記第３の電力変換回路に電圧が与えられた状態で前記第３の電力変換回路の動作を開始し、前記第１の直流コンデンサの電圧が前記第１の閾値電圧に達しかつ前記第２の直流コンデンサの電圧が前記第２の閾値電圧に達すると、前記第２の電力変換回路の動作を開始させる、請求項１に記載の電力変換装置。     The load is a voltage source load that spontaneously generates a voltage,
    The control unit is
    The first power conversion circuit starts operating in a state in which a voltage is applied to the first power conversion circuit from the input power source, and a voltage is applied to the third power conversion circuit from the voltage source load. In this state, the operation of the third power conversion circuit is started, the voltage of the first DC capacitor reaches the first threshold voltage, and the voltage of the second DC capacitor reaches the second threshold voltage. Then, the power conversion device according to claim 1, which starts the operation of the second power conversion circuit.
  8. 　前記制御部は、前記第２の電力変換回路の動作開始時に前記第２の電力変換回路のデューティ比を徐々に上昇させる、請求項７に記載の電力変換装置。 The power conversion device according to claim 7, wherein the control unit gradually increases the duty ratio of the second power conversion circuit when the operation of the second power conversion circuit is started.
  9. 　前記制御部は、前記第１、第２および第３の電力変換回路の全てが動作を開始した後に、前記第１の直流コンデンサの電圧が第１の目標電圧に追従しかつ前記第２の直流コンデンサの電圧が第２の目標電圧に追従するように前記第１、第２および第３の電力変換回路を制御し、
    　前記第１の閾値電圧は前記第１の目標電圧よりも低く、前記第２の閾値電圧は前記第２の目標電圧よりも低い、請求項１～８のいずれか一項に記載の電力変換装置。     The control unit controls the voltage of the first DC capacitor to follow a first target voltage and the second DC voltage after all of the first, second and third power conversion circuits start operating. Controlling the first, second and third power conversion circuits so that the voltage of the capacitor follows the second target voltage,
    The power conversion device according to claim 1, wherein the first threshold voltage is lower than the first target voltage, and the second threshold voltage is lower than the second target voltage. ..
  10. 　前記第１の電力変換回路は昇圧回路であり、前記第１の閾値電圧は、前記入力電源から前記第１の電力変換回路に与えられる電圧よりも高い、請求項１～９のいずれか一項に記載の電力変換装置。 10. The first power conversion circuit is a booster circuit, and the first threshold voltage is higher than a voltage applied from the input power supply to the first power conversion circuit. The power converter according to.
  11. 　前記第３の電力変換回路は降圧回路であり、前記第２の閾値電圧は、前記第３の電力変換回路から前記負荷に与えられる電圧よりも高い、請求項１～１０のいずれか一項に記載の電力変換装置。 The third power conversion circuit is a step-down circuit, and the second threshold voltage is higher than a voltage applied to the load from the third power conversion circuit. The power converter described.
  12. 　前記入力電源は交流電源であり、
    　前記第１の電力変換回路は、前記入力電源からの交流電圧を直流電圧へ変換するＡＣ／ＤＣコンバータを含み、
    　前記第３の電力変換回路は、前記第２の電力変換回路から出力された直流電圧を変圧するＤＣ／ＤＣコンバータを含む、請求項１～１１のいずれか一項に記載の電力変換装置。     The input power source is an AC power source,
    The first power conversion circuit includes an AC/DC converter that converts an AC voltage from the input power supply into a DC voltage,
    The power conversion device according to any one of claims 1 to 11, wherein the third power conversion circuit includes a DC/DC converter that transforms the DC voltage output from the second power conversion circuit.
  13. 　前記入力電源は直流電源であり、
    　前記第１の電力変換回路は、前記入力電源からの直流電圧を変圧するＤＣ／ＤＣコンバータを含み、
    　前記第３の電力変換回路は、前記第２の電力変換回路から出力された直流電圧を交流電圧へ変換するインバータを含む、請求項１～１２のいずれか一項に記載の電力変換装置。     The input power source is a DC power source,
    The first power conversion circuit includes a DC/DC converter that transforms a DC voltage from the input power source,
    The power conversion device according to any one of claims 1 to 12, wherein the third power conversion circuit includes an inverter that converts the DC voltage output from the second power conversion circuit into an AC voltage.
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