JP2010098819A - Voltage conversion device and method of controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent overheating of a reactor in a power conversion device comprising the reactor. <P>SOLUTION: A converter 12 includes IGBT elements Q1 and Q2 and the reactor L1 to which voltage switched by the IGBT elements Q1 and Q2 is applied and it voltage-converts DC voltage from a DC power supply B. The reactor L1 has a characteristic whose inductance changes in accordance with a size of reactor current IL passing the reactor L1. A controller 30 changes a carrier frequency switching the IGBT elements Q1 and Q2 and controls a boosting converter 12 in accordance with inductance of the reactor L1. The controller 30 changes the carrier frequency so that the carrier frequency becomes high as inductance of the reactor L1 becomes low. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a voltage converter and a method for controlling the voltage converter, and more specifically to a voltage converter having a reactor as a constituent element and a method for controlling the voltage converter.

As one of the voltage converters, a converter configured to include a chopper circuit that converts a DC voltage using a reactor is used (see, for example, Patent Documents 1 to 4). In such a chopper circuit, a switched voltage is applied to the reactor, and a current flowing through the reactor (hereinafter also referred to as a reactor current) undergoes a temporal change in inclination according to the inductance of the reactor. That is, an alternating current (hereinafter also referred to as a ripple current) depending on the switching frequency is superimposed on the reactor current. This ripple current increases as the inductance of the reactor decreases.
JP 2007-300799 A JP 2003-116280 A JP 2004-135465 A JP-A-7-147775

  As a reactor used in the converter as described above, there is a reactor whose inductance changes depending on the magnitude of the reactor current. As an example, in a reactor having a core composed of a dust core (powder magnetic core) formed by compression molding metal magnetic powder (for example, fine magnetic particles mainly composed of molybdenum or the like), the inductance increases as the reactor current increases. Some have reduced properties.

  Therefore, when a converter is configured including such a reactor, when the reactor current increases, the inductance of the reactor decreases, and thus the ripple current increases. As a result, the amount of heat generated by the core increases with electromagnetic energy conversion in the reactor, which may cause thermal destruction of the core. Moreover, there is a concern that the voltage conversion efficiency in the converter may be reduced due to the temperature rise of the reactor due to the core heat generation.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to prevent overheating of the reactor in the voltage conversion device configured to include the reactor.

  According to an aspect of the present invention, a voltage conversion device includes a switching element and a reactor to which a voltage switched by the switching element is applied, a voltage converter that converts a DC voltage from a DC power supply, and a reactor. And a control device for controlling the voltage converter by changing the carrier frequency for switching the switching element according to the inductance of the switching element.

  Preferably, the voltage conversion device further includes a current sensor for detecting a reactor current passing through the reactor. The control device holds the relationship between the reactor current and the inductance of the reactor in advance, and changes the carrier frequency based on the output of the current sensor so that the carrier frequency increases as the inductance decreases with reference to the relationship.

  Preferably, the voltage conversion device further includes a current sensor for detecting a reactor current passing through the reactor and a voltage sensor for detecting a voltage applied to the reactor. The control device calculates the inductance of the reactor from the temporal change of the reactor current and the voltage applied to the reactor based on the outputs of the current sensor and the voltage sensor, and the carrier frequency increases as the calculated inductance decreases. Change the carrier frequency.

  According to another aspect of the present invention, a control of a voltage conversion device including a switching element and a reactor to which a voltage switched by the switching element is applied, and including a voltage converter that converts a DC voltage from a DC power supply. A method of detecting a reactor current passing through a reactor based on an output of a current sensor, and a relationship between the reactor current and the inductance of the reactor is held in advance, and the relationship is determined based on the detected reactor current. And a step of changing the carrier frequency so that the carrier frequency becomes higher as the inductance of the reactor becomes lower.

  According to another aspect of the present invention, a control of a voltage conversion device including a switching element and a reactor to which a voltage switched by the switching element is applied, and including a voltage converter that converts a DC voltage from a DC power supply. A method of detecting a reactor current passing through a reactor based on an output of a current sensor, a step of detecting a voltage applied to the reactor based on an output of a voltage sensor, and a temporal change of the detected reactor current And a step of calculating the inductance of the reactor from the voltage applied to the reactor, and a step of changing the carrier frequency so that the carrier frequency increases as the calculated inductance decreases.

  According to the present invention, in a voltage conversion device configured to include a reactor, overheating of the reactor can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 1 is a schematic block diagram of a motor drive device to which a voltage conversion device according to an embodiment of the present invention is applied.

  Referring to FIG. 1, motor drive device 100 includes DC power supply B, voltage sensors 10, 13, 18, current sensors 11, 24, system relays SR 1, SR 2, capacitors C 1, C 2, and boost converter 12. And an inverter 14 and a control device 30.

  AC motor M1 is a drive motor for generating torque for driving drive wheels of a hybrid vehicle or an electric vehicle. Alternatively, this motor has the function of a generator driven by an engine, and operates as an electric motor for the engine, for example, can be incorporated into a hybrid vehicle so that the engine can be started. Also good.

  Boost converter 12 includes a reactor L1, IGBTs (Insulated Gate Bipolar Transistor) elements Q1, Q2, and diodes D1, D2. In the present embodiment, the IGBT element is described as a representative example of the “switching element”.

  Reactor L1 has one end connected to the power supply line of DC power supply B and the other end connected to the intermediate point between IGBT element Q1 and IGBT element Q2, that is, between the emitter of IGBT element Q1 and the collector of IGBT element Q2. The

  IGBT elements Q1, Q2 are connected in series between the power supply line and the earth line. The collector of IGBT element Q1 is connected to the power supply line, and the emitter of IGBT element Q2 is connected to the ground line. In addition, diodes D1 and D2 that allow current to flow from the emitter side to the collector side are connected between the collector and emitter of the IGBT elements Q1 and Q2, respectively.

  Here, in the present embodiment, reactor L1 has a characteristic that the inductance changes in accordance with a current (hereinafter also referred to as a reactor current) IL flowing through reactor L1. As an example, a reactor having a core made of a dust core obtained by compression molding metal magnetic powder has a characteristic that the inductance decreases as the reactor current IL increases, as will be described later.

  Inverter 14 includes a U-phase arm 15, a V-phase arm 16, and a W-phase arm 17. U-phase arm 15, V-phase arm 16, and W-phase arm 17 are provided in parallel between the power supply line and the earth line.

  U-phase arm 15 includes IGBT elements Q3 and Q4 connected in series, V-phase arm 16 includes IGBT elements Q5 and Q6 connected in series, and W-phase arm 17 includes IGBT elements Q7 and Q7 connected in series. Consists of Q8. Further, diodes D3 to D8 that flow current from the emitter side to the collector side are connected between the collectors and emitters of the IGBT elements Q3 to Q8, respectively.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of AC motor M1. In other words, AC motor M1 is a three-phase permanent magnet motor, and is configured such that one end of three coils of U, V, and W phases is commonly connected to the midpoint, and the other end of the U-phase coil is IGBT element Q3. The other end of the V-phase coil is connected to the intermediate point of IGBT elements Q5 and Q6, and the other end of the W-phase coil is connected to the intermediate point of IGBT elements Q7 and Q8, respectively.

  The DC power source B is a chargeable / dischargeable secondary battery, and is made of, for example, nickel hydride or lithium ion. Note that the present invention is not limited to this, and any device that can generate a DC voltage, for example, a capacitor, a solar cell, a fuel cell, or the like can be applied. Voltage sensor 10 detects DC voltage Vb output from DC power supply B, and outputs the detected DC voltage Vb to control device 30. System relays SR1 and SR2 are turned on / off by signal SE from control device 30.

  Capacitor C1 smoothes DC voltage Vb supplied from DC power supply B, and outputs the smoothed DC voltage Vb to boost converter 12. Current sensor 11 detects reactor current IL flowing through reactor L1 of boost converter 12 and outputs the detected reactor current IL to control device 30.

  Boost converter 12 boosts the DC voltage supplied from capacitor C1 and supplies the boosted voltage to capacitor C2. More specifically, when boosting converter 12 receives signal PWU from control device 30, boosting converter 12 boosts the DC voltage according to the period during which NPN transistor Q2 is turned on by signal PWU, and supplies the boosted voltage to capacitor C2.

  Further, when boost converter 12 receives signal PWD from control device 30, boost converter 12 steps down the DC voltage supplied from inverter 14 via capacitor C <b> 2 and charges DC power supply B. However, it goes without saying that boost converter 12 may be applied to a circuit configuration that performs only a boost function.

  Capacitor C <b> 2 smoothes the DC voltage from boost converter 12 and supplies the smoothed DC voltage to inverter 14. The voltage sensor 13 detects the voltage across the capacitor C2, that is, the output voltage Vm of the boost converter 12 (corresponding to the input voltage to the inverter 14, the same applies hereinafter), and the detected output voltage Vm is controlled by the control device 30. Output to.

  When a DC voltage is supplied from the capacitor C2, the inverter 14 converts the DC voltage into an AC voltage based on the signal PWMI from the control device 30, and drives the AC motor M1. As a result, AC motor M1 is driven so as to generate torque specified by torque command value TR. Further, the inverter 14 converts the AC voltage generated by the AC motor M1 into a DC voltage based on the signal PWMC from the control device 30 during regenerative braking of the hybrid vehicle or electric vehicle on which the motor drive device 100 is mounted, The converted DC voltage is supplied to boost converter 12 via capacitor C2. Note that regenerative braking here refers to braking with regenerative power generation when the driver driving a hybrid vehicle or electric vehicle performs foot braking, or turning off the accelerator pedal while driving, although the foot brake is not operated. This includes decelerating the vehicle (or stopping acceleration) while generating regenerative power.

  Current sensor 24 detects motor current MCRT flowing through AC motor M1 and outputs the detected motor current MCRT to control device 30.

  The control device 30 includes a torque command value TR and a motor rotational speed MRN input from an externally provided ECU (Electronic Control Unit), a DC voltage Vb from the voltage sensor 10, an output voltage Vm from the voltage sensor 13, and a current. Based on the motor current MCRT from the sensor 24, a signal PWU for driving the boost converter 12 and a signal PWMI for driving the inverter 14 are generated by a method described later, and the generated signal PWU and signal PWMI are respectively generated. Output to boost converter 12 and inverter 14.

  The signal PWU is a signal for driving the boost converter 12 when the boost converter 12 converts the DC voltage from the capacitor C1 into the output voltage Vm. Then, when boost converter 12 converts DC voltage Vb to output voltage Vm, control device 30 performs feedback control on output voltage Vm, and controls boost converter 12 so that output voltage Vm becomes commanded voltage command Vdccom. A signal PWU for driving is generated. A method for generating the signal PWU will be described later.

  Control device 30 also adjusts the carrier frequency for turning on / off IGBT elements Q1, Q2 of boost converter 12. A method for adjusting the carrier frequency will be described later.

  Further, when control device 30 receives a signal indicating that the hybrid vehicle or the electric vehicle has entered the regenerative braking mode from an external ECU, signal PWMC for converting the AC voltage generated by AC motor M1 into a DC voltage. Is output to the inverter 14. In this case, the IGBT elements Q3 to Q8 of the inverter 14 are switching-controlled by the signal PWMC. Thereby, the inverter 14 converts the AC voltage generated by the AC motor M <b> 1 into a DC voltage and supplies it to the boost converter 12.

  Further, when receiving a signal indicating that the hybrid vehicle or the electric vehicle has entered the regenerative braking mode from the external ECU, the control device 30 generates a signal PWD for stepping down the DC voltage supplied from the inverter 14, The generated signal PWD is output to boost converter 12. As a result, the AC voltage generated by AC motor M1 is converted into a DC voltage, stepped down, and supplied to DC power supply B.

  Furthermore, control device 30 generates signal SE for turning on / off system relays SR1, SR2 and outputs the signal SE to system relays SR1, SR2.

FIG. 2 is a functional block diagram of the control device 30 in FIG.
Referring to FIG. 2, control device 30 includes a motor control phase voltage calculation unit 40, an inverter PWM signal conversion unit 42, an inverter input voltage command calculation unit 50, a feedback voltage command calculation unit 52, a duty ratio. A conversion unit 54 and a frequency adjustment unit 56 are included.

  Motor control phase voltage calculation unit 40 receives output voltage Vm of boost converter 12, that is, an input voltage to inverter 14 from voltage sensor 13, and receives motor current MCRT flowing in each phase of AC motor M <b> 1 from current sensor 24. The torque command value TR is received from the external ECU. The motor control phase voltage calculation unit 40 calculates the voltage to be applied to the coils of each phase of the AC motor M1 based on these input signals, and the calculated result is the inverter PWM signal conversion unit 42. To supply.

  Based on the calculation result received from motor control phase voltage calculation unit 40, inverter PWM signal conversion unit 42 generates signal PWMI that actually turns on / off each IGBT element Q3-Q8 of inverter 14, and generates the signal PWMI. The signal PWMI is output to the IGBT elements Q3 to Q8 of the inverter 14.

  Thereby, each IGBT element Q3-Q8 is switching-controlled, and controls the electric current sent through each phase of AC motor M1 so that AC motor M1 may output the commanded command. In this way, the motor drive current is controlled, and a motor torque corresponding to the torque command value TR is output.

  On the other hand, inverter input voltage command calculation unit 50 calculates an optimum value (target value) of the inverter input voltage based on torque command value TR and motor rotational speed MRN, that is, voltage command Vdccom, and calculates the calculated voltage command Vdccom. Output to the feedback voltage command calculation unit 52.

  Feedback voltage command calculation unit 52 calculates feedback voltage command Vdccom_fb based on output voltage Vm of boost converter 12 from voltage sensor 13 and voltage command Vdccom from inverter input voltage command calculation unit 50. Feedback voltage command Vdccom_fb is output to duty ratio converter 54.

  The duty ratio conversion unit 54 outputs from the voltage sensor 13 based on the battery voltage Vb from the voltage sensor 10, the output voltage Vm from the voltage sensor 13, and the feedback voltage command Vdccom_fb from the feedback voltage command calculation unit 52. The duty ratio DR for setting the voltage Vm to the feedback voltage command Vdccom_fb from the feedback voltage command calculation unit 52 is calculated, and the calculated duty ratio DR is output to the frequency adjustment unit 56. Then, duty ratio conversion unit 54 generates a signal PWU for turning on / off IGBT elements Q1, Q2 of boost converter 12 based on calculated duty ratio DR and carrier frequency fc from frequency adjustment unit 56. The generated signal PWU is output to IGBT elements Q1 and Q2 of boost converter 12.

  Note that increasing the on-duty of IGBT element Q2 on the lower side of boost converter 12 increases the power storage in reactor L1, so that a higher voltage output can be obtained. On the other hand, increasing the on-duty of the upper IGBT element Q1 lowers the voltage of the power supply line. Therefore, the voltage of the power supply line can be controlled to an arbitrary voltage equal to or higher than the output voltage of the DC power supply B by controlling the duty ratio of the IGBT elements Q1 and Q2.

  The frequency adjustment unit 56 variably sets the carrier frequency fc according to the reactor current IL from the current sensor 11. This is because the inductance L of the reactor L1 through which the reactor current IL passes changes in accordance with the magnitude of the reactor current IL. Hereinafter, setting operation of carrier frequency fc in frequency adjusting unit 56 according to the present embodiment will be described with reference to FIGS.

(Carrier frequency setting method)
FIG. 3 is a diagram showing the relationship between the inductance L of the reactor L1 and the reactor current IL.

  Referring to FIG. 3, the inductance L of reactor L1 shows a characteristic that decreases as reactor current IL increases. Due to such characteristics, the magnitude of the alternating current (hereinafter also referred to as ripple current) superimposed on the reactor current IL changes according to the magnitude of the reactor current IL.

  Specifically, by performing switching control of IGBT elements Q1 and Q2 of boost converter 12 (FIG. 1), ripple current Irp that periodically increases and decreases is superimposed on reactor current IL. The period in which the ripple current Irp increases or decreases coincides with the control period of the boost converter 12. The control cycle of boost converter 12 can be obtained from carrier frequency fc for turning on / off IGBT elements Q1, Q2.

  When the peak peak value of the ripple current Irp is ΔIrp, it is known that ΔIrp is expressed by the following equation (1).

VL = L · (ΔIrp / Δt) (1)
However, VL is a voltage switched by IGBT elements Q1 and Q2 (hereinafter also referred to as reactor voltage) applied to both ends of reactor L1, and Δt is a cycle in which ripple current Irp increases or decreases, that is, control of boost converter 12 It is a period.

  In the above equation (1), the relationship of the following equation (2) is established between ΔIrp and the inductance L of the reactor L1.

ΔIrp = VL / L · Δt (2)
As can be seen from the equation (2), when the reactor voltage VL is constant, the peak peak value ΔIrp of the ripple current increases as the inductance L decreases. When the peak peak value ΔIrp of the ripple current increases, the amount of heat generated by the core increases with electromagnetic energy conversion in the reactor L1. This can cause the core to undergo thermal destruction. Moreover, the voltage conversion efficiency in a boost converter may fall by the temperature rise of the reactor by core heat_generation | fever.

  Therefore, as a means for reducing the peak peak value ΔIrp of the ripple current, in the present embodiment, the carrier frequency fc according to the inductance L so that the control period Δt of the boost converter 12 becomes shorter as the inductance L becomes lower. It is set as the structure which switches.

  FIG. 4 shows temporal changes in reactor current IL before and after switching of carrier frequency fc. The line k1 in the figure shows the reactor current IL before switching of the carrier frequency fc, and the line k2 in the figure shows the reactor current IL after switching of the carrier frequency fc.

  The carrier frequency fc is switched by changing the carrier frequency fc to a lower frequency while maintaining the duty ratio in the switching control of the IGBT elements Q1 and Q2. As a result, the peak peak value ΔIrp of the ripple current can be reduced when the carrier frequency fc is relatively low (line k2) compared to when the carrier frequency fc is relatively high (line k1).

  Thus, in the present embodiment, by adopting a configuration in which the carrier frequency fc is switched according to the inductance L of the reactor L1, even when the inductance L decreases according to the magnitude of the reactor current IL, the reactor L1. It is possible to prevent the core from being overheated.

  FIG. 5 is a diagram showing the relationship between reactor current IL and carrier frequency fc. The relationship of FIG. 5 is obtained by calculating the upper limit value of the reactor current IL that can be passed through the reactor L1 for each carrier frequency based on the relationship between the inductance L and the reactor current IL shown in FIG. is there. Specifically, in accordance with the upper limit value of the peak peak value ΔIrp of the ripple current that can be passed through the preset reactor L1, the lower limit values L1, L2 of the inductance L allowed for each carrier frequency, that is, the allowed reactors The upper limit values I1 and I2 of the current IL are derived.

  Referring to FIG. 5, carrier frequency fc is set to increase as reactor current IL increases. Specifically, when the reactor current IL is less than I1, the carrier frequency fc is set to f0, and when the reactor current IL is equal to or greater than I1 and less than I2, the carrier frequency fc is a frequency f1 higher than f0 (> When the reactor current IL is equal to or greater than I2, the carrier frequency fc is set to a frequency f2 (> f1> f0) higher than f1. Therefore, since the carrier frequency fc increases as the inductance L decreases, it is possible to suppress an increase in the peak peak value ΔIrp of the ripple current.

  The frequency adjusting unit 56 (FIG. 2) stores the relationship between the reactor current IL and the carrier frequency fc shown in FIG. 5 in a ROM (Read Only Memory) (not shown) as a carrier frequency map, and the reactor current from the current sensor 11 is stored. If read from the ROM, the carrier frequency fc is switched using the rear frequency map according to IL.

  Note that the carrier frequencies f0, f1, and f2 in FIG. 5 take into account that the higher the carrier frequency fc, the more the peak peak value ΔIrp of the ripple current can be reduced, while the loss (switching loss) of the boost converter 12 increases. Thus, the frequency is set such that the sum of the loss of boost converter 12 and the loss of reactor L1 is not increased.

  In the example of FIG. 5, the carrier frequency fc is changed stepwise according to the reactor current IL. However, the carrier frequency fc can be changed continuously according to the reactor current IL. is there.

  FIG. 6 is a flowchart of control related to switching of the carrier frequency fc in the control device 30 of FIG. A series of control processing according to the flowchart shown in FIG. 6 is realized by executing a program stored in advance in the control device 30 at a predetermined cycle.

  Referring to FIG. 6, when frequency reactor 56 of control device 30 receives reactor current IL from current sensor 11 (FIG. 1) (step S01), carrier frequency map (FIG. 5) is read from ROM and read. The carrier frequency fc is set according to the reactor current IL using the carrier frequency map.

  Specifically, the frequency adjustment unit 56 determines whether or not the reactor current IL is greater than or equal to a predetermined first threshold value I1 (step S02). When reactor current IL is lower than first threshold value I1 (NO in step S02), frequency adjustment unit 56 sets carrier frequency fc to a predetermined frequency f0 (step S04).

  In contrast, when reactor current IL is equal to or greater than first threshold value I1 (YES in step S02), frequency adjustment unit 56 determines whether reactor current IL is equal to or greater than a predetermined second threshold value I2. It is determined whether or not (step S03). When reactor current IL is lower than second threshold I2 (NO in step S03), frequency adjustment unit 56 sets carrier frequency fc to a frequency f1 higher than predetermined frequency f0 (step S05).

  On the other hand, when reactor current IL is greater than or equal to second threshold value I2 (YES in step S03), frequency adjustment unit 56 causes frequency adjustment unit 56 to set carrier frequency fc higher than frequency f1. The frequency is set to f2 (step S06).

(Example of change)
Regarding the switching operation of the carrier frequency fc in the frequency adjustment unit 56, as described above, the carrier frequency fc is switched according to the reactor current IL using the relationship between the inductance L and the reactor current IL held in advance. In addition to this, as described in the present modification, it is also possible to calculate the inductance L of the reactor L1 and switch the carrier frequency fc in accordance with the calculated inductance L.

  FIG. 7 is a flowchart of control related to switching of the carrier frequency fc in the control device 30 of FIG. A series of control processing according to the flowchart shown in FIG. 7 is realized by executing a program stored in advance in the control device 30 at a predetermined cycle.

  Referring to FIG. 7, frequency adjustment unit 56 of control device 30 receives reactor current IL from current sensor 11 (FIG. 1) (step S11), and also receives reactor voltage VL from voltage sensor 18 (FIG. 1) ( Step S12). Reactor voltage VL can be detected by the output of voltage sensor 18 (FIG. 1) arranged to measure the voltage difference between both ends of reactor L1.

  Then, frequency adjustment unit 56 obtains temporal change dIL / dt of reactor current IL based on the difference between reactor current IL at the previous program execution and reactor current IL input in step S11.

  Further, the frequency adjusting unit 56 calculates the inductance L according to the equation (3) from the reactor voltage VL input in step S12 and the temporal change dIL / dt of the reactor current IL (step S13).

L = VL · (dt / dIL) (3)
Then, the frequency adjustment unit 56 determines whether or not the calculated inductance L exceeds a predetermined first threshold value L1 (step S14). If inductance L exceeds first threshold value L1 (YES in step S14), frequency adjustment unit 56 sets carrier frequency fc to a predetermined frequency f0 (step S16).

  On the other hand, when the inductance L is equal to or less than the first threshold L1 (in the case of NO in step S14), the frequency adjustment unit 56 determines whether the inductance L exceeds a predetermined second threshold L2. Judgment is made (step S15). When the inductance L exceeds the second threshold L2 (YES in step S15), the frequency adjustment unit 56 sets the carrier frequency fc to a frequency f1 higher than the predetermined frequency f0 (step S17).

  On the other hand, when the inductance L is less than or equal to the second threshold L2 (NO in step S15), the frequency adjusting unit 56, the frequency adjusting unit 56, the carrier frequency fc is higher than the frequency f1. f2 is set (step S18).

  Regarding the correspondence between the present embodiment and the configuration of the present invention, the boost converter 12 corresponds to the “voltage converter” in the present invention, and the current sensor 11 corresponds to the “current sensor” in the present invention. The voltage sensor 18 corresponds to the “voltage sensor” in the present invention, and the control device 30 corresponds to the “control device” in the present invention.

  In the present embodiment, the configuration example in which the voltage conversion device is mounted on the vehicle has been described. However, the application of the present invention is not limited to such a case. In other words, regardless of the type of equipment or system to be applied, and as long as the configuration includes a reactor, the configuration of the voltage conversion device is not particularly limited, and it can be confirmed that the present invention can be applied. Describe.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic block diagram of the motor drive device provided with the voltage converter by embodiment of this invention. It is a functional block diagram of the control apparatus shown in FIG. It is a figure which shows the relationship between the inductance L of the reactor L1, and the reactor current IL. It is a figure which shows the time change of the reactor current IL before and behind switching of the carrier frequency fc. It is a figure which shows the relationship between reactor current IL and carrier frequency fc. 2 is a flowchart of control related to switching of a carrier frequency fc in the control device of FIG. 1. 2 is a flowchart of control related to switching of a carrier frequency fc in the control device of FIG. 1.

Explanation of symbols

  10, 13, 18 Voltage sensor, 11, 24 Current sensor, 12 Boost converter, 14 Inverter, 15 U-phase arm, 16 V-phase arm, 17 W-phase arm, 30 Controller, 40 Motor control phase voltage calculation unit, 42 PWM signal conversion unit, 50 inverter input voltage command calculation unit, 52 feedback voltage command calculation unit, 54 duty ratio conversion unit, 56 frequency control unit, 100 motor drive device, B DC power supply, C1, C2 capacitor, D1-D8 diode, L1 reactor, M1 AC motor, Q1-Q8 IGBT element, SR1, SR2 System relay.

Claims (5)

A voltage converter that includes a switching element and a reactor to which a voltage switched by the switching element is applied, and converts a DC voltage from a DC power supply;
A voltage conversion device comprising: a control device that controls the voltage converter by changing a carrier frequency for switching the switching element according to the inductance of the reactor. A current sensor for detecting a reactor current passing through the reactor;
The control device holds a relationship between the reactor current and the inductance of the reactor in advance, and based on the output of the current sensor, the carrier frequency is increased as the inductance decreases with reference to the relationship. The voltage conversion apparatus according to claim 1, wherein the carrier frequency is changed. A current sensor for detecting a reactor current passing through the reactor;
A voltage sensor for detecting a voltage applied to the reactor,
The control device calculates the inductance of the reactor from the temporal change of the reactor current and the voltage applied to the reactor based on the outputs of the current sensor and the voltage sensor, and the calculated inductance decreases as the calculated inductance decreases. The voltage conversion device according to claim 1, wherein the carrier frequency is changed so that the carrier frequency becomes higher. A control method for a voltage conversion device including a switching element and a reactor to which a voltage switched by the switching element is applied, and including a voltage converter that converts a DC voltage from a DC power source,
Detecting a reactor current passing through the reactor based on an output of a current sensor;
A relationship between the reactor current and the inductance of the reactor is held in advance, and the carrier frequency is increased based on the detected reactor current so that the carrier frequency increases as the inductance of the reactor decreases with reference to the relationship. And a step of changing the frequency. A control method for a voltage conversion device including a switching element and a reactor to which a voltage switched by the switching element is applied, and including a voltage converter that converts a DC voltage from a DC power source,
Detecting a reactor current passing through the reactor based on an output of a current sensor;
Detecting a voltage applied to the reactor based on an output of a voltage sensor;
Calculating the inductance of the reactor from the detected temporal change of the reactor current and the voltage applied to the reactor;
And a step of changing the carrier frequency so that the carrier frequency becomes higher as the calculated inductance becomes lower.

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