JP2019022400A - Power conversion device - Google Patents

Abstract

To effectively convert power between a DC power source and an AC power source or an AC load.SOLUTION: A DC power source 10 and an AC power source 40 or an AC load 30 are connected by an isolation transformer 20, and power is exchanged between the DC power source 10 and the AC power source 40 or the AC load 30. The isolation transformer 20 comprises: a primary-side coil 22 connected to the DC power source 10, the primary-side coil 22 being such that one end and the other end are alternately switched by a switch 24 and connected to one end of the DC power source 10, an intermediate tap is connected to the other end of the DC power source 10, and electric current alternately flows in the intermediate tap and in one end or the other end; and a secondary-side coil 26 disposed opposite the primary-side coil 22, the secondary-side coil 26 being connected to the AC power source 40 or the AC load 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion device in which a DC power source and an AC power source or an AC load are connected by an insulating transformer, and power is exchanged between the DC power source and the AC power source or the AC load.

  In Non-Patent Document 1, DC power from a battery is converted into AC by an inverter, a motor is driven, the motor is disconnected from the inverter at a charging station, AC from an external power source is input to the inverter via an insulation transformer, A system for charging a battery by converting into direct current by an inverter is disclosed.

  Patent Document 1 discloses a system in which direct current power from a battery is converted into alternating current by an inverter, a motor is driven, and alternating current from an external power source is converted into direct current to charge the battery. The alternating current from the external power source is supplied to the inverter after being converted from alternating current → direct current → alternating current → direct current.

US Patent Publication US2014 / 0340004A1 Japanese Patent Laid-Open No. 2006-67123

Saeid Haghbin et. Al. "An integrated motor drive and battery fast charger station for plug-in Vehicles", 13th Spanish Portuguese Conference on Electrical Engineering (13CHLIE) (2013), Chalmers University of Technology

  In the system of Non-Patent Document 1, since the DC power from the battery is converted to AC by an inverter and the motor is driven, the motor drive voltage becomes equal to or less than the battery voltage. Moreover, since AC power (for example, 50 Hz) from the AC power source is supplied to the transformer, the transformer becomes large.

  Further, even in the system of Patent Document 1, the motor drive voltage becomes equal to or lower than the battery voltage. Further, when power from an AC power source is used, the number of conversions is large and the number of parts is also large.

  The present invention is a power conversion apparatus in which a DC power source and an AC power source or an AC load are connected by an insulating transformer, and power is exchanged between the DC power source and the AC power source or the AC load. A primary coil connected to a power source, one end and the other end of which are alternately switched and connected to one end of a DC power source by a switch, and an intermediate tap is connected to the other end of the DC power source. A primary side coil through which current alternately flows between one end or the other end, and a secondary side coil disposed opposite to the primary side coil, the secondary side coil connected to an AC power source or an AC load; Have

  The present invention is also a power conversion apparatus in which a DC power source and an AC power source or an AC load are connected via an insulation transformer, and exchange power between the DC power source and the AC power source or the AC load. The power source is a three-phase AC power source, the AC load is a three-phase AC load, the isolation transformer is a three-phase single-phase transformer with three intermediate taps corresponding to three phases, Each phase transformer is a primary coil connected to a DC power source, and one end and the other end are alternately switched and connected to one end of the DC power source by a switch circuit, and an intermediate tap is connected to the other end of the DC power source. A primary side coil that is connected and a current flows alternately between the intermediate tap and one end or the other end, and a secondary side coil that is disposed opposite to the primary side coil, and is connected to an AC power source or an AC load. Secondary side It has a yl, respectively, one side is a phase transformer secondary coil, connected to each phase of a corresponding AC power or AC load, respectively, the other side is connected to the midpoint.

  Furthermore, it is preferable to have a relay for controlling on / off of the connection between the secondary coil and the AC load.

  In addition, in the case of the first mode, a first mode for exchanging power between the DC power source and the AC power source and a second mode for exchanging power between the DC power source and the AC load are switched by the mode selection signal. On / off of the switch circuit is controlled based on the voltage phase of the AC power supply. In the second mode, it is preferable to control on / off of the switch circuit based on the rotational phase of the AC load.

  In the present invention, power can be exchanged between a DC power source and an AC load or AC power source with a relatively simple configuration. In addition, since an insulation transformer is used, power can be transported by electrically insulating the system power supply and the DC power supply. By changing the winding ratio of the insulation transformer, a high voltage can be obtained even if the DC power supply voltage is low. The AC load can be driven.

It is a figure which shows the whole structure of the power converter device which concerns on embodiment. It is a figure which shows the structure of a whole control block. It is a figure which shows the structure of a motor control block. It is a figure which shows the structure of a system | strain control block. It is a figure which shows the circuit for 1 phase of a primary side. It is a figure which shows the flow of the electric current at the time of power running and regeneration / charging. It is a figure which shows the waveform of each part. It is a figure which shows a three-phase voltage. It is a figure which shows the operation example of a motor drive. It is a figure which shows the operation example of battery charging.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described herein.

  Drawing 1 is a figure showing the composition of the power converter concerning an embodiment. One end (+ end or − end) of battery 10 as a DC power source is connected to one end of reactor 12, and a capacitor is connected between the other end of reactor 12 and the other end (− end or + end) of battery 10. 14 is connected. The reactor 12 and the capacitor 14 function as a filter that removes high frequencies.

  The other end of the reactor 12 is connected to the primary side of the isolation transformer 20 via a bidirectional switch (switch circuit) 24. The insulation transformer 20 includes a three-phase primary coil 22 (22U, 22V, 22W) of U phase, V phase, and W phase. The other end of the reactor 12 is connected to both ends of the three-phase primary coil 22 of the insulating transformer 20 via six bidirectional switches 24. That is, it is connected to both ends of the primary side coil 22U via the bidirectional switches 24UP and 24UN, is connected to both ends of the primary side coil 22V via the bidirectional switches 24VP and 24VN, and is connected via the bidirectional switches 24WP and 24WN. Are connected to both ends of the primary coil 22W. The other end of the battery 10 is connected to the intermediate taps of the three primary coils 22U, 22V, 22W.

  Therefore, by alternately turning on the bidirectional switches 24UP and 24UN, the current from the one end to the intermediate tap and the current in the opposite directions from the other end to the intermediate tap are alternately switched to the U-phase primary coil 22U. Can be shed. By controlling the bidirectional switches 24VP, 24VN, 24WP, and 24WN in the same manner, currents in opposite directions can be alternately supplied to the V-phase and W-phase primary coils 22V and 22W.

  In addition, the reactor 12 and the capacitor | condenser 14 act as a filter, and it prevents that alternating current is applied to the battery 10 from the bidirectional | two-way switch 24 side.

  The three-phase insulating transformer 20 has a three-phase secondary coil 26 (26U, 26V, 26W) facing the three-phase primary coil 22. Accordingly, secondary currents corresponding to the primary currents flowing through the primary coils 22U, 22V, and 22W of the respective phases flow through the secondary coils 26U, 26V, and 26W of the respective phases.

  Each phase of a motor (AC motor) 30 as an AC load is connected to the three-phase secondary coil 26 of the insulating transformer 20 via a relay 32. That is, one end of the secondary coil 26U is connected to the U phase of the motor 30, one end of the secondary coil 26V is connected to the V phase, and one end of the secondary coil 26W is connected to the W phase, and the secondary coils 26U, 26V, 26W are connected. Is connected to a neutral point N of the motor 30. Accordingly, the motor 30 can be driven by supplying motor currents having different phases by 120 ° from the three-phase secondary coil 26 to each phase of the motor 30.

  A system power supply 40 is also connected to the three-phase secondary coil 26 of the insulating transformer 20 as an AC power supply (for example, three-phase, 200 V, 50 Hz). One end of the secondary side coils 26U, 26V, 26W is connected to each phase of the three-phase system power supply 40 via a reactor 42 (42U, 42V, 42W) and an EMI filter 44. By arranging the three reactors 42, the system power supply 40 is a circuit equivalent to the motor 30. Further, the EMI filter 44 prevents outflow of electromagnetic noise. That is, by arranging the EMI filter 44 between the reactor 42 and the system power supply 40, an EMI (Electro Magnetic Interference) countermeasure can be taken.

  In such a system, by controlling on / off of the bidirectional switch 24, power exchange between the primary side and the secondary side of the isolation transformer 20 can be performed. Also, by turning on the relay 32, a motor drive mode is established in which the motor 30 is driven by the electric power from the battery 10, and by turning off the relay, the electric power from the AC system power supply 40 and the charging mode for charging the battery 10 are provided. Become. Here, in the motor drive mode, the AC system power supply 40 may be disconnected from the insulating transformer 20. In the illustrated example, only the V phase of the motor 30 is connected to the secondary side of the insulating transformer 20 in the charging mode, but the V phase may also be disconnected.

  Each phase current on the secondary side of the insulating transformer 20 is detected by three current sensors 34. The motor current may be detected in two phases. The rotor rotation angle of the motor 30 is detected by a rotation angle sensor 36. Further, the voltage of the AC system power supply 40 is detected by the voltage sensor 38. A rotational angular velocity ω is detected from the detected rotor rotation angle, and the voltage phase of the system power supply is detected from the voltage of the system power supply.

  These detection values are supplied to the control block 50, and the control block 50 controls on / off of the bidirectional switch 24 in accordance with the supplied detection signal.

"Overall Configuration of Control Block"
FIG. 2 shows the configuration of the control block 50. When the mode selection signal input by the user is in the motor drive mode, the relay 32 is turned on, and in the charge mode, a relay signal for turning off the relay 32 is output.

  When the mode selection signal is the motor drive mode, the motor control unit 52 is selected and its operation is permitted, and when it is in the charge mode, the system control unit 54 is selected and its operation is permitted.

  In the motor drive mode, the motor control unit 52 calculates the current command iq * and the phase command θ * from the rotation angular velocity ω (the rotation phase θ calculated from the rotation angular velocity ω) and the angular velocity command ω *. In the charging mode, the system control unit 54 calculates the current command id *, iq * and the phase command θ * from the target power P * and the detection phase θg.

  The obtained current commands id *, iq * and phase command θ * are supplied to the control processing unit 56, where three-phase voltage commands vu *, vv *, vw * are calculated, and the gate signal generation unit 58 To be supplied. The gate signal generator 58 generates and outputs gate signals for turning on and off the six bidirectional switches 24.

"Configuration of motor control"
FIG. 3 shows the configuration of the motor control block in the control block 50. The motor control unit 52 has a speed detector 60 and detects the rotational angular velocity ω from the temporal change of the rotor rotational angle obtained by the rotational angle sensor 36 of the motor 30. The angular velocity ω is output to the integrator 62 as the rotational phase θ of the rotor. The motor control unit 52 may calculate the d-axis current command id * and the q-axis current command iq * based on the required torque command for the motor 30.

  Further, the angular velocity ω is subtracted from the angular velocity command ω * by the adder 64 to obtain an error signal, which is input to the velocity control unit 66. The speed control unit 66 calculates a q-axis current command iq * on the dq axis for eliminating the error from the error signal, and outputs this.

  The q-axis current command iq * from the speed control unit 66 and the phase θ from the integrator 62 are supplied to the control processing unit 56. Specifically, the phase θ from the integrator 62 is supplied to the uvw / dq conversion unit 68. The uvw / dq conversion unit 68 is supplied with the three-phase currents iu, iv, iw detected by the current sensor 34, and uvw / dq (3-axis / 2-axis) conversion is performed in consideration of the phase θ. . As a result, the d-axis current id and the q-axis current iq of the motor 30 are obtained. In this example, d-axis current command id * = 0.

  The d-axis current id is supplied to the adder 70, where an error from the d-axis current command id * is calculated, and the error is supplied to the controller 72. The controller 76 calculates and outputs a d-axis voltage command vd * from the supplied error.

  The q-axis current iq is supplied to the adder 74, an error from the q-axis current command iq * is calculated, and the calculated error is supplied to the controller 76. The controller 76 calculates and outputs a d-axis voltage command vq * from the supplied error.

  The d-axis voltage command vd * and the q-axis voltage command vq * from the controllers 72 and 76 are input to the dq / uvw conversion unit 78, and three-phase voltage commands u *, v *, Output as w *.

  The calculation of the three-phase voltage commands u *, v *, and w * is not different from normal motor vector control.

  Three-phase voltage commands Vu *, Vv *, Vw * from the control processing unit 56 are input to the gate signal generation unit 58. The gate signal generation unit 58 includes three comparators 80 (80U, 80V, 80W). These comparators 80 are input with triangular wave carriers, and the voltage commands Vu *, Vv *, Vw * are respectively compared with the carriers and a PWM control signal is output. The outputs from the comparators 80U, 80V, 80W and their inverted signals are converted into PWM signals SUP, SUN, SVP, SVN, Output as SWP and SWN.

`` System control configuration ''
FIG. 4 shows the configuration of the system control block in the control block 50. Here, charging the battery 10 with the power from the system power supply 40 is basically the same as charging the battery 10 with the regenerative power of the motor 30, and the same control as in the case of the regeneration is performed. The frequency (for example, 50 Hz) and voltage (for example, 200 V) of the system power supply are constant, and this corresponds to the case where the electric frequency of the motor 30 is 50 Hz and the voltage is 200 V.

  The system control unit 54 includes a power control unit 90 and a phase detector 92. A user input or a preset target power P * is input to the power control unit 90. The power control unit 90 calculates a d-axis current command id * and a q-axis current command iq * for obtaining the target power P * as charging power from the three-phase alternating current (frequency 50 Hz) of the system power supply 200V.

  The phase detector 92 detects the phase (voltage phase) θg of the system power from the voltage signal obtained by the voltage sensor 38. Since the phases of the three phases are different from each other by 120 °, one-phase detection may be performed.

  The d-axis current command id *, the q-axis current command iq *, and the phase θ from the system control unit 54 are supplied to the control processing unit 56.

  The control processing unit 56 is the same as the motor control block described above, and receives the input d-axis current command id *, q-axis current command iq *, and three-phase voltage commands vu *, vv *, vw * from the phase θ. Calculate and supply to the gate signal generator 58. Then, the gate signal generator 58 generates the gate signal of the bidirectional switch 24 in the same manner as the motor control block, and controls the switching.

"Control action"
FIG. 5 shows a circuit diagram (U phase) for one phase. In this example, the bidirectional switch 24 is composed of two switching elements (parallel connection of a transistor and a diode). That is, the switching element is configured by connecting a diode that allows current to flow from the source to the drain of the N-channel transistor. Then, the two switching elements are connected to each other to form one bidirectional switch 24.

  In the illustrated example, the bidirectional switch 24UP is configured by switching elements SUP1 and SUP2, and the bidirectional switch 24UN is configured by switching elements SUN1 and SUN2. As the bidirectional switch 24, various configurations can be adopted as described in Patent Document 2.

  FIG. 6 shows how the current for one phase flows. When power is supplied to the motor 30, the switching element SUP2 is turned on as shown in FIG. 6 (a), whereby a current flows through the primary coil 22U from the top to the bottom in the figure. Further, as shown in FIG. 6B, by turning on the switching element SUN2, a current flows through the primary coil 22U from the bottom to the top in the drawing. Accordingly, an alternating current flows through the secondary coil 26U, but the motor coil connected to the secondary coil 26U is controlled by controlling the ratio of the ON time (duty ratio) between the switching element SUP2 and the switching element SUN2. A desired phase current can be passed.

  During charging in which the battery 10 is charged with regenerative power from the motor 30 or power from the system power source 40, the switching element SUP1 is turned on as shown in FIG. Current flows upward from the top. Further, as shown in FIG. 6D, by turning on the switching element SUN1, a current flows through the primary coil 22U from the top to the bottom in the figure. Therefore, by controlling the ratio (duty ratio) between the ON time of the switching element SUP2 and the switching element SUN2, the battery 10 is connected to the secondary coil 26U according to the phase current from the system power supply side or the motor coil. A charging current can be obtained.

"PWM control"
FIG. 7 shows signal waveforms of the respective parts of the gate signal generation unit 58. The U-phase voltage command Vu * and the carrier are compared. When the voltage command Vu * is larger, the SUP is at a high level. Further, when the voltage command Vu * is smaller, SUN is at a high level. With such a signal, the states of FIG. 6A and FIG. 6B occur alternately. Thereby, the U-phase applied voltage of the motor 30 of the secondary coil 26U becomes a voltage that repeats +-, and the U-phase current of the motor 30 obtains a predetermined phase current (iu).

  In the charge mode, the charge current can be obtained from each phase current on the secondary side by the same vector control (current command id *, iq *).

  FIG. 8 shows comparisons and phase voltages in the U, V, and W phases. In this way, three-phase PWM signals that are 120 ° different from each other are obtained, thereby obtaining a three-phase alternating current.

"Operation example"
FIG. 9 shows an example of motor drive operation. The rotational speed is increased by increasing the output torque in the state where the rotational speed is 0 rpm. By setting the torque to 0, the rotational speed becomes constant. By making the torque negative, the rotational speed decreases, and by making the torque zero, the rotational speed becomes constant.

  In such a case, the electric power gradually increases by keeping the torque constant while the rotational speed increases. By setting the torque to 0, the power is also reduced to 0. By making the torque negative, the power becomes negative and regenerative power is obtained. The regenerative power decreases as the rotational speed decreases. When the torque is reduced to 0, the power is also reduced to 0.

  The motor voltage has the same tendency as the rotation speed as an AC voltage. The motor current tends to be similar to the torque.

  Thus, by determining the torque command according to the output request and the charge request of the motor 30 and setting the corresponding current commands id * and iq *, the motor output and regeneration according to the request can be performed. .

  FIG. 10 shows the charging operation of the battery 10 by the electric power from the system power supply 40. The system voltage is a state of the system power supply 40, and a three-phase voltage with a constant 120 ° phase difference is constantly output and does not change.

  Switching of the bidirectional switch 24 causes a desired system current to flow, whereby system power is output and corresponding battery power is generated. A corresponding charging current flows. Desired charging can be performed by setting the battery power according to the charging current to obtain the target power P *.

"Effect of the embodiment"
In this way, by controlling the bidirectional switch 24, bidirectional energy transfer (power conversion) can be controlled using an insulating transformer. In particular, in this embodiment, the insulation transformer has a function of electrically insulating the battery side and the system side during charging.

  In addition, by using the winding voltage ratio (power conversion ratio) of the transformer when the motor is driven, it becomes possible to use a lower battery voltage than the motor voltage. That is, when the winding ratio of the insulating transformer is 1, the relationship between the motor applied voltage Vu and the battery voltage Vbat is Vu = 0.5 · Vbat · msinωt, but if the winding ratio of the insulating transformer is N, Vu = 0.5 · Vbat · N · msinωt, and the motor applied voltage can be increased N times. When the voltage ratio of the transformer is 1: 2, 200 = 200 × 2/2 is obtained in order to obtain a motor applied voltage of 200 V, so that the battery voltage Vbat = 200 V.

  As described above, the insulating transformer performs an insulating function when charging, and functions to increase the battery voltage when the motor is driven. The power converter of this embodiment has a relatively simple configuration and can perform power conversion with a small number of parts. Furthermore, noise countermeasures by EMI are possible.

  In the present embodiment, DC / AC bidirectional power conversion can be performed by a single power conversion, and power conversion efficiency can be improved.

  By using the power conversion circuit of this embodiment for a PHV car (hybrid car that can be charged from a commercial power source) / EV car (electric car) equipped with a battery, an AC load (eg, an electric motor) is driven from the DC power source. . In addition, the battery can be charged from an AC power supply (for example, a three-phase system power supply) by bidirectional control.

DESCRIPTION OF SYMBOLS 10 Battery, 12 Reactor, 14 Capacitor, 20 Isolation transformer, 22 Primary side coil, 24 Bidirectional switch, 26 Secondary side coil, 30 Motor, 32 Relay, 34 Current sensor, 36 Rotation angle sensor, 38 Voltage sensor, 40 System power supply, 42 reactor, 44 EMI filter, 50 control block, 52 motor control unit, 54 system control unit, 56 control processing unit, 58 gate signal generation unit.

Claims (4)

A power conversion device in which a DC power supply and an AC power supply or an AC load are connected by an insulating transformer, and the power is exchanged between the DC power supply and the AC power supply or the AC load,
The insulation transformer
A primary coil connected to a DC power source, one end and the other end of which are alternately switched and connected to one end of the DC power source by a switch, and an intermediate tap is connected to the other end of the DC power source, A primary coil in which current flows alternately between one end or the other end;
A secondary coil disposed opposite to the primary coil, the secondary coil connected to an AC power supply or an AC load;
Having
Power conversion device. A power conversion device in which a DC power source and an AC power source or an AC load are connected via an insulation transformer, and exchange power between the DC power source and the AC power source or the AC load,
The AC power supply is a three-phase AC power supply, the AC load is a three-phase AC load, the insulation transformer is a single-phase transformer with three intermediate taps corresponding to three phases,
Each phase transformer of three single-phase transformers with intermediate taps
A primary coil connected to a DC power source, one end and the other end of which are alternately switched and connected to one end of the DC power source by a switch circuit, and an intermediate tap is connected to the other end of the DC power source, And a primary side coil in which current alternately flows between one end or the other end,
A secondary coil disposed opposite to the primary coil, the secondary coil connected to an AC power supply or an AC load;
Each with
One side of the secondary coil of each phase transformer is connected to each phase of the corresponding AC power supply or AC load, and the other side is connected to the midpoint.
Power conversion device. The power converter according to claim 1 or 2,
further,
The power converter device which has a relay which controls ON / OFF of both connection between a secondary side coil and alternating current load. It is a power converter device as described in any one of Claims 1-3,
A first mode for exchanging power between the DC power supply and the AC power supply by a mode selection signal and a second mode for exchanging power between the DC power supply and the AC load are switched,
In the first mode, on / off of the switch circuit is controlled based on the voltage phase of the AC power supply, and in the second mode, on / off of the switch circuit is controlled based on the rotational phase of the AC load.
Power conversion device.