JP2017022927A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device capable of reducing a conduction loss.SOLUTION: A power conversion device 15 includes: a first inverter 20 including switching elements 211 to 216 and reflux diodes 221 to 226; and a second inverter 30 including switching elements 311 to 316 and reflux diodes 321 to 326. Turning on the switching elements 211 to 216, 311 to 316 enables electric conduction from the high potential side to the low potential side. The reflux diodes 221 to 226, 321 to 326 are connected in parallel to the switching elements 211 to 216, 311 to 316, respectively and permit electric conduction from the low potential side to the high potential side. The power conversion device also comprises a control unit 60 that, in a one side drive mode, selects whether all phases of upper arm elements are turned on in the first inverter 20 or second inverter 30 to be made to be a neutral point or all phases of lower arm elements are turned on, depending on current conducted in coils 11 to 13. Thereby, a conduction loss can be reduced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion device.

  Conventionally, an inverter drive system that converts electric power of a motor by two inverters is known. For example, in Patent Document 1, the phase of the fundamental wave component of the pulse width modulation signal (hereinafter referred to as “PWM”) of the first inverter system and the second inverter system at a high voltage is 180 [°. By shifting, the two power supplies are electrically connected in series, and the motor is driven by the sum of the two power supply voltages. Further, in Patent Document 1, at the time of a low voltage, either one of the upper arm or the lower arm of the first inverter system or the second inverter system is simultaneously turned on for three phases, and the other is PWM driven.

JP 2006-238686 A

In Patent Document 1, there is no mention of selection of whether the upper arm is fixed to ON or the lower arm is fixed to ON in the low voltage mode.
This invention is made | formed in view of the above-mentioned subject, The objective is to provide the power converter device which can reduce conduction | electrical_connection loss.

The power conversion device of the present invention converts power of a rotating electrical machine having a plurality of phases of windings, and includes a first inverter, a second inverter, and a control unit.
The first inverter is connected to one end of the winding and the first voltage source.
The second inverter is connected to the other end of the winding and the second voltage source.
The control unit controls the first inverter and the second inverter.

  The first inverter and the second inverter each have a switching element and a reflux element. The switching element is an upper arm element connected to the high potential side or a lower arm element connected to the low potential side of the upper arm element, and is energized from the high potential side to the low potential side when turned on. Is possible. The reflux element is connected in parallel to each of the switching elements and allows energization from the low potential side to the high potential side.

In the one-side drive mode, one of the first inverter and the second inverter is neutralized by turning on all phases of the upper arm element or all phases of the lower arm element, and the other of the first inverter and the second inverter is Control is performed according to the drive demand of the rotating electrical machine. In the one-side drive mode, the control unit energizes the winding to turn on all phases of the upper arm element or all phases of the lower arm element in the first inverter or the second inverter to be neutralized. Select according to the current.
Thereby, the conduction | electrical_connection loss in the inverter which becomes neutral point can be reduced.

It is a schematic block diagram which shows the power converter device by one Embodiment of this invention. It is explanatory drawing explaining the electricity supply path | route in the one side drive mode in one Embodiment of this invention. It is explanatory drawing explaining the conduction | electrical_connection loss of IGBT and a diode. It is a flowchart explaining the arm selection process by one Embodiment of this invention. It is a time chart explaining the arm selection process by one Embodiment of this invention. It is a time chart explaining the arm selection process by one Embodiment of this invention. It is a schematic block diagram which shows the power converter device by other embodiment of this invention.

Hereinafter, a power converter according to the present invention will be described with reference to the drawings.
(One embodiment)
The power converter device by 1st Embodiment of this invention is shown in FIGS.
As shown in FIG. 1, the rotating electrical machine drive system 1 includes a motor generator 10 as a rotating electrical machine and a power conversion device 15.

  The motor generator 10 is a so-called “main motor” that is applied to an electric vehicle such as an electric vehicle or a hybrid vehicle and generates torque for driving drive wheels (not shown). The motor generator 10 has a function as an electric motor for driving the drive wheels, and a function as a generator that generates electric power by being driven by kinetic energy transmitted from an engine or drive wheels (not shown). In this embodiment, the case where the motor generator 10 functions as an electric motor will be mainly described.

Motor generator 10 is a three-phase AC rotating machine, and includes U-phase coil 11, V-phase coil 12, and W-phase coil 13. The U-phase coil 11, the V-phase coil 12, and the W-phase coil 13 correspond to “windings”, and the U-phase coil 11, the V-phase coil 12, and the W-phase coil 13 are hereinafter appropriately referred to as “coils 11 to 13”.
In the present embodiment, the current flowing through the U-phase coil 11 is defined as a U-phase current Iu, the current flowing through the V-phase coil 12 is defined as a V-phase current Iv, and the current flowing through the W-phase coil 13 is defined as a W-phase current Iw.

The power conversion device 15 converts the power of the motor generator 10, and includes a first inverter 20, a second inverter 30, a control unit 60, and the like.
The first inverter 20 is a three-phase inverter that switches energization to the coils 11 to 13, and includes switching elements 211 to 216 and return diodes 221 to 226. The second inverter 30 is a three-phase inverter that switches energization to the coils 11 to 13, and includes switching elements 311 to 316 and freewheeling diodes 321 to 326.

The switching elements 211 to 216 and 311 to 316 are IGBTs (insulated gate bipolar transistors), and the on / off operation is controlled by the control unit 60. When the switching element 211 is turned on, energization from the high potential side to the low potential side is allowed, and when it is turned off, the energization is interrupted.
The free-wheeling diodes 221 to 226 and 321 to 326 are connected in parallel with the switching elements 211 to 216 and 311 to 316, respectively, and allow energization from the low potential side to the high potential side.

  In the first inverter 20, the switching elements 211 to 213 are connected to the high potential side, and the switching elements 214 to 216 are connected to the low potential side. The first high potential side wiring 27 that connects the high potential side of the switching elements 211 to 213 is connected to the positive electrode of the first battery 41, and the first low potential side wiring that connects the low potential side of the switching elements 214 to 216. 28 is connected to the negative electrode of the first battery 41.

  One end 111 of the U-phase coil 11 is connected to the connection point 24 of the U-phase switching elements 211 and 214, and one end 121 of the V-phase coil 12 is connected to the connection point 25 of the V-phase switching elements 212 and 215. One end 131 of the W-phase coil 13 is connected to the connection point 26 of the W-phase switching elements 213 and 216. That is, the first inverter 20 is connected between the coils 11, 12, 13 and the first battery 41.

  In the second inverter 30, switching elements 311 to 313 are connected to the high potential side, and switching elements 314 to 316 are connected to the low potential side. The second high potential side wiring 37 that connects the high potential side of the switching elements 311 to 313 is connected to the positive electrode of the second battery 42, and the second low potential side wiring that connects the low potential side of the switching elements 314 to 316. 38 is connected to the negative electrode of the second battery 42.

The other end 112 of the U-phase coil 11 is connected to the connection point 34 of the U-phase switching elements 311 and 314, and the other end 122 of the V-phase coil 12 is connected to the connection point 35 of the V-phase switching elements 312 and 315. The other end 132 of the W-phase coil 13 is connected to the connection point 36 of the W-phase switching elements 313 and 316. That is, the second inverter 30 is connected between the coils 11, 12, 13 and the second battery 42.
Hereinafter, the switching elements 211 to 213 and 311 to 313 connected to the high potential side are referred to as “upper arm elements”, and the switching elements 214 to 216 and 314 to 316 connected to the low potential side are referred to as “lower arm elements”.

A first battery 41 as a first voltage source, which is a chargeable / dischargeable DC power source such as a lithium ion battery, is connected to the first inverter 20 and can exchange power with the motor generator 10 via the first inverter 20. Provided.
A second battery 42 as a second voltage source, which is a DC power source that can be charged and discharged, such as a lithium ion battery, is connected to the second inverter 30 and can exchange power with the motor generator 10 via the second inverter 30. Provided.

The first capacitor 43 is connected to the first high potential side wiring 27 and the first low potential side wiring 28. The first capacitor 43 is a smoothing capacitor that smoothes the current from the first battery 41 to the first inverter 20 side or the current from the first inverter 20 to the first battery 41 side.
The second capacitor 44 is connected to the second high potential side wiring 37 and the second low potential side wiring 38. The second capacitor 44 is a smoothing capacitor that smoothes the current from the second battery 42 to the second inverter 30 or the current from the second inverter 30 to the second battery 42.

The control unit 60 is mainly composed of a microcomputer and performs various arithmetic processes. Each processing in the control unit 60 may be software processing by executing a program stored in advance by the CPU, or may be hardware processing by a dedicated electronic circuit.
The control unit 60 includes an inverter control unit 61, a current calculation unit 62, a temperature calculation unit 63, and the like.

The inverter control unit 61 controls the first inverter 20 and the second inverter 30. Specifically, the inverter control unit 61 switches the switching elements 211 to 216, 311 based on command values relating to driving of the motor generator 10, such as the torque command value trq ^* and the current command values Iu ^* , Iv ^* , Iw ^*. A control signal for controlling the on / off operation of 316 is generated. The generated control signal is output to the gates of the switching elements 211 to 216 and 311 to 316 via a driver circuit (not shown). Switching elements 211 to 216 and 311 to 316 are turned on and off in accordance with a control signal, whereby DC power of batteries 41 and 42 is converted into AC and supplied to motor generator 10. Thereby, driving of motor generator 10 is controlled by control unit 60 via first inverter 20 and second inverter 30.

The current calculator 62 estimates the phase currents Iu, Iv, Iw based on the current command values Iu ^* , Iv ^* , Iw ^* of each phase. Further, the maximum phase that is the phase having the maximum absolute value of the phase currents Iu, Iv, and Iw is specified.
The temperature calculation unit 63 estimates the first inverter temperature T1 that is the temperature of the first inverter 20 and the second inverter temperature T2 that is the temperature of the second inverter 30 based on the phase currents Iu, Iv, Iw, and the like.

  Here, the drive mode of the motor generator 10 will be described. The drive mode in the rotating electrical machine drive system 1 of the present embodiment includes the “one-side drive mode” that uses the power of the first battery 41 or the second battery 42 and the power of the first battery 41 and the second battery. "Double-sided drive mode" to be used and driven is included.

When the motor generator 10 is driven with a relatively light load, the one-side drive mode is set.
When the motor generator 10 is driven by the electric power of the first battery 41, one of all the phases of the upper arm elements 311 to 313 or all the phases of the lower arm elements 314 to 316 is turned on and the other is turned off. Then, the second inverter 30 is neutralized.
Hereinafter, turning on all phases of the upper arm elements 311 to 313 as appropriate is referred to as “fixing the upper arm on”, and turning on all phases of the lower arm elements 314 to 316 is referred to as “fixing the lower arm on. It is said. The same applies to the case where the first inverter 20 is neutralized.

  When driving the motor generator 10 with the electric power of the first battery 41, the first inverter 20 is controlled by PWM control or the like according to the drive request of the motor generator 10. For PWM control, “sine wave PWM control” in which the amplitude of the fundamental wave corresponding to the command is equal to or less than the amplitude of the carrier wave such as a triangular wave, and “overmodulation PWM control” in which the amplitude of the fundamental wave is larger than the amplitude of the carrier wave including. Further, the inverter that is not neutralized is not limited to PWM control, and may be controlled in any manner such as rectangular wave control.

  When the motor generator 10 is driven by the power of the second battery 42, one of all phases of the upper arm elements 211 to 213 or all phases of the lower arm elements 214 to 216 of the first inverter 20 is turned on and the other is turned off. Then, the first inverter 20 is neutralized. Further, the second inverter 30 is controlled by PWM control or the like according to the drive request of the motor generator 10.

In the one-side drive mode, one inverter is neutralized, so that the switching loss is reduced and the efficiency at the time of low output can be increased as compared with the both-side drive mode described later.
In addition, when the voltage of the first battery 41 and the voltage of the second battery 42 are different and the drive request can be satisfied with the output with the lower voltage, the high voltage side is neutralized and driven on the low voltage side, Switching loss can be further reduced. Note that the inverter to be neutralized can be appropriately selected according to the drive request, the remaining battery level, and the like.

When the motor generator 10 is driven with a relatively high load that cannot satisfy the drive request with the electric power of the first battery 41 or the second battery 42, the both-side drive mode using the both-side power source is set. In the double-side drive mode, the first inverter 20 and the second inverter 30 are controlled so that the first battery 41 and the second battery 42 can be regarded as being electrically connected in series.
Here, a case where the first inverter 20 is PWM controlled by comparing the first fundamental wave F1 and the carrier wave, and the second inverter 30 is PWM controlled by comparing the second fundamental wave F2 and the carrier wave will be described as an example. To do.

In the double-side drive mode, the phases of the first fundamental wave F1 and the second fundamental wave F2 are inverted. In other words, the first fundamental wave F1 and the second fundamental wave F2 are out of phase by approximately 180 [°]. By setting the phase difference between the first fundamental wave F1 and the second fundamental wave F2 to 180 [°], it can be considered that the first battery 41 and the second battery 42 are electrically connected in series. A voltage corresponding to the sum of the voltage of the first battery 41 and the voltage of the second battery 42 can be applied to the motor generator 10.
The phase difference between the first fundamental wave F1 and the second fundamental wave F2 is 180 [°], but a voltage corresponding to the sum of the voltage of the first battery 41 and the voltage of the second battery 42 is set to the motor generator 10. It is assumed that a deviation that can be applied to is allowed.

The amplitude of the first fundamental wave F1 and the amplitude of the second fundamental wave F2 may be equal or different.
The first fundamental wave F1 and the second fundamental wave F2 may have similar waveforms such that both are sine waves. In addition, the waveforms of the first fundamental wave F1 and the second fundamental wave F2 are different as in the case where one of the first inverter 20 or the second inverter 30 is subjected to sinusoidal PWM control and the other is subjected to overmodulation PWM control. May be. Alternatively, rectangular wave control may be performed in which the amplitude is infinite and each element is switched on and off every half cycle of the fundamental waves F1 and F2. The rectangular wave control can be said to be 180-degree energization control. Moreover, it is good also as 120 degree electricity supply control based on fundamental wave F1 and F2 instead of rectangular wave control.

When the amplitudes and waveforms of the fundamental waves F <b> 1 and F <b> 2 are equal, the elements that are turned on in each phase are upside down in the first inverter 20 and second inverter 30. Note that when the amplitudes and waveforms of the fundamental waves F1 and F2 are different, the elements that are turned on in each phase are not necessarily upside down in the first inverter 20 and the second inverter 30.
Thus, the motor generator 10 can be driven with high efficiency by switching between the one-side drive mode and the two-side drive mode in accordance with the drive request of the motor generator 10. Further, motor generator 10 may be driven in a drive mode other than the above-described one-side drive mode or both-side drive mode.

Hereinafter, the description will focus on the one-side drive mode.
An example in which the second inverter 30 is neutralized is shown in FIG. In FIG. 2, switching elements 311 to 316 that are turned on are indicated by solid lines, and switching elements 311 to 316 that are turned off are indicated by broken lines. In the present embodiment, the current flowing in the direction of the inverter that becomes neutral is positive, and the current in the opposite direction is negative. That is, in the example of FIG. 2, the current flowing from the first inverter 20 side to the second inverter 30 side is positive, and the current flowing from the second inverter 30 side to the first inverter 20 side is negative.

2A shows a case where the upper arm elements 311 to 313 are fixed on, and FIG. 2B shows a case where the lower arm elements 314 to 316 are fixed on.
As shown in FIG. 2A, for example, when the U-phase current Iu is supplied in the positive direction and the V-phase current Iv and the W-phase current Iw are supplied in the negative direction, as shown by an arrow UD, a free-wheeling diode in the U-phase As indicated by arrows VT and WT, the switching elements 312 and 313 are energized in the V-phase and the W-phase.
That is, when the second inverter 30 is neutralized by fixing the upper arm elements 311 to 313 to be on, the phase where the phase current is positive is the freewheeling diodes 321 to 323, and when the phase current is negative, the switching elements 311 to 313 are used. Current flows through

As shown in FIG. 2B, for example, when the U-phase current Iu is supplied in the positive direction and the V-phase current Iv and the W-phase current Iw are supplied in the negative direction, the switching element is used in the U-phase as indicated by the arrow UT. As indicated by arrows VD and WD, the freewheeling diodes 325 and 326 are energized in the V phase and the W phase as indicated by arrows VD and WD.
That is, when the second inverter 30 is neutralized by fixing the lower arm elements 314 to 316 to ON, the switching element 314 to 316 is a phase in which the phase current is positive, and the freewheeling diodes 324 to 326 is negative. Current flows through

Although not shown, the case where the first inverter 20 is neutralized will be described. When neutralizing the first inverter 20, the current flowing from the second inverter 30 side to the first inverter 20 side is positive, and the current flowing from the first inverter 20 side to the second inverter 30 side is negative.
When neutralizing the first inverter 20, when the first inverter 20 is neutralized by fixing the upper arm elements 211 to 213 to be on, the phases having a positive phase current are the free-wheeling diodes 221 to 223, In the negative phase, current flows through the switching elements 211 to 213.
Further, when the first inverter 20 is neutralized by fixing the lower arm elements 214 to 216 to ON, the switching element 214 to 216 is a phase having a positive phase current, and the freewheeling diodes 224 to 226 is a phase having a negative phase current. Current flows through
That is, in the inverter that is neutralized, whether the current flows through the switching element or the free wheeling diode varies depending on the direction of the current and the arm that is fixed on.

  By the way, the output characteristics are different between the IGBT and the diode. An example of output characteristics of the IGBT and the diode is shown in FIG. As shown in FIG. 3, in the region where the current is smaller than the threshold current Ith, the conduction loss of the diode is smaller than that of the IGBT, and in the region where the current is larger than the threshold current Ith, the conduction loss of the IGBT is smaller than that of the diode. The threshold current Ith varies depending on the types of elements used for the switching elements 211 to 216 and 311 to 316 and the free wheel diodes 221 to 226 and 321 to 326. Further, the threshold current Ith also changes depending on the temperature. For example, as the temperature increases, the threshold current Ith decreases. In the present embodiment, it is assumed that the temperature and the threshold current Ith are associated with each other and stored in advance in a map or the like.

  Therefore, in the present embodiment, in order to reduce the loss of the power converter 15 as a whole, the phase currents Iu, Iv, In accordance with Iw and inverter temperatures T1 and T2, an arm to be fixed on is selected in the inverter that is neutralized.

  An arm selection process for selecting an arm to be fixed on in the inverter to be neutralized will be described based on the flowchart shown in FIG. As described above, the inverter to be neutralized is selected according to a drive request or the like, and the arm selection process is executed by the control unit 60 at a predetermined interval.

In the first step S101, the temperature calculation unit 63 calculates inverter temperatures T1 and T2. Here, the temperature of the inverter that is neutralized may be calculated, and the temperature calculation of the inverter that is not neutralized may be omitted. Hereinafter, “step” in step S101 is omitted, and is simply referred to as “S”. The same applies to the other steps.
In S102, the threshold current Ith is determined by map calculation or the like based on the temperature of the inverter that is neutralized.
In S103, the current calculation unit 62 calculates the phase currents Iu, Iv, and Iw, and specifies the maximum phase.

  In S104, inverter control unit 61 determines whether or not maximum phase current Imax, which is the maximum phase current, is positive. When it is determined that maximum phase current Imax is not positive, that is, negative (S104: NO), the process proceeds to S106. When it is determined that the maximum phase current Imax is positive (S104: YES), the process proceeds to S105.

  In S105, inverter control unit 61 determines whether or not maximum phase current Imax is smaller than threshold current Ith. When it is determined that the maximum phase current Imax is smaller than the threshold current Ith (S105: YES), the process proceeds to S107. When it is determined that the maximum phase current Imax is equal to or greater than the threshold current Ith (S105: NO), the process proceeds to S108.

  In S106, when the maximum phase current Imax is determined to be negative (S104: NO), the inverter control unit 61 determines whether the absolute value of the maximum phase current Imax is smaller than the threshold current Ith. . When it is determined that the absolute value of the maximum phase current Imax is smaller than the threshold current Ith (S106: YES), the process proceeds to S108. When it is determined that the absolute value of the maximum phase current Imax is greater than or equal to the threshold current Ith (S106: NO), the process proceeds to S107.

When the maximum phase current Imax is positive and smaller than the threshold current Ith (S104: YES and S105: YES), or when the maximum phase current Imax is negative and the absolute value of the maximum phase current Imax is greater than or equal to the threshold current Ith (S104: NO and S106: NO) In S107, the inverter control unit 61 fixes the upper arm on in the neutralizing inverter.
When maximum phase current Imax is positive and greater than or equal to threshold current Ith (S104: YES and S105: NO), or when maximum phase current Imax is negative and absolute value of maximum phase current Imax is threshold current Ith In S108 which shifts to the case where it is smaller (S104: NO and S106: YES), the inverter control unit 61 fixes the lower arm on in the inverter to be neutralized.

Details of the arm selection processing will be described based on the time charts of FIGS. 5 and 6, the U-phase current Iu is indicated by a solid line, the V-phase current Iv is indicated by a one-dot chain line, and the W-phase current Iw is indicated by a two-dot chain line. Here, the second inverter 30 will be described as being neutralized.
FIG. 5 is an example when the peaks of the phase currents Iu, Iv, and Iw are smaller than the threshold current Ith. As described with reference to FIG. 3, in the region where the current is smaller than the threshold current Ith, the loss of the freewheeling diodes 321 to 326 is smaller than that of the switching elements 311 to 316, so that the maximum phase current Imax passes through the freewheeling diodes 321 to 326. Select the arm to be fixed on.

In the period PH, since the maximum phase current Imax is positive and smaller than the threshold current Ith (S104: YES and S105: YES in FIG. 4), the upper arm elements 311 to 313 are fixed on. The second inverter 30 is neutralized. In the period PL, since the maximum phase current Imax is negative and smaller than the threshold current Ith (S104: NO and S108: YES), the second arm elements 314 to S316 are fixed to ON by the second arm element 314 to S316. The inverter 30 is neutralized.
Thus, the maximum phase current Imax passes through the freewheeling diodes 321 to 326, so that the loss can be reduced.

FIG. 6 is an example when the peaks of the phase currents Iu, Iv, and Iw are larger than the threshold current Ith.
In the period PH1, since the maximum phase current Imax is positive and smaller than the threshold current Ith (S104: YES and S105: YES), the upper arm is set so that the maximum phase current Imax passes through the freewheeling diodes 321 to 323. The second inverter 30 is neutralized by fixing the elements 311 to 313 on.
In the period PL2, the maximum phase current Imax is positive and equal to or greater than the threshold current Ith (S104: YES and S105: NO), so that the maximum phase current Imax passes through the lower arm elements 314 to 316. The second inverter 30 is neutralized by fixing the lower arm elements 314 to 316 on.

In the period PL1, since the maximum phase current Imax is negative and the absolute value of the maximum phase current Imax is smaller than the threshold current Ith (S104: NO and S106: YES), the maximum phase current Imax is determined from the free-wheeling diodes 324 to 324. The second inverter 30 is neutralized by fixing the lower arm elements 314 to 316 on so as to pass through 326.
In the period PH2, since the maximum phase current Imax is negative and the absolute value of the maximum phase current Imax is greater than or equal to the threshold current Ith (S104: NO and S106: NO), the maximum phase current Imax is the upper arm element. The second inverter 30 is neutralized by fixing the upper arm elements 311 to 313 on so as to pass 311 to 313.

  In the present embodiment, in the inverter that is neutralized, the maximum phase current Imax is supplied to the switching elements 211 to 216 and 311 to 316 and the freewheeling diodes 221 to 226 and 321 to 326 with the smaller conduction loss. Select the arm to be fixed on. Thereby, compared with the case where the arm to be fixed on is not changed in the one-side drive mode, the conduction loss in the inverter that is neutralized can be reduced, so that the loss of the power converter 15 as a whole can be reduced. Can improve efficiency.

As described above in detail, the power conversion device 15 of the present embodiment converts the power of the motor generator 10 having the multiple-phase coils 11 to 13, and includes the first inverter 20, the second inverter 30, and the like. The control part 60 is provided.
The first inverter 20 is connected to one ends 111, 121, 131 of the coils 11, 12, 13 and the first battery 41.
The second inverter 30 is connected to the other ends 112, 122, 132 of the coils 11, 12, 13 and the second battery 42.
The control unit 60 controls the first inverter 20 and the second inverter 30.

The first inverter 20 includes switching elements 211 to 216 and freewheeling diodes 221 to 226, and the second inverter 30 includes switching elements 311 to 316 and freewheeling diodes 321 to 326.
The switching elements 211 to 216 and 311 to 316 are upper arm elements 211 to 213 and 311 to 313 connected to the high potential side, or lower arm elements 214 to 216 and 314 to 316 connected to the low potential side. When turned on, it is possible to energize from the high potential side to the low potential side. The free-wheeling diodes 221 to 226 and 321 to 326 are connected in parallel to the switching elements 211 to 216 and 311 to 316, respectively, and allow energization from the low potential side to the high potential side.

In the one-side drive mode, one of the first inverter 20 and the second inverter 30 is neutralized by turning on all phases of the upper arm element or all phases of the lower arm element, and the first inverter 20 or the second inverter 30 The other of these is controlled according to the drive request of the motor generator 10. In the one-side drive mode, the control unit 60 determines whether to turn on all phases of the upper arm element or all phases of the lower arm element in the first inverter 20 or the second inverter 30 that are neutralized. The selection is made according to the current supplied to 11 to 13.
Thereby, the conduction loss in the inverter which is neutralized can be reduced, and the efficiency is improved.

A current value at which the magnitude of the conduction loss is switched between the switching elements 211 to 216 and 311 to 316 and the freewheeling diodes 221 to 226 and 321 to 326 is defined as a threshold current Ith.
The control unit 60 compares the maximum phase current Imax, which is the current of the phase having the largest absolute value of the current supplied to the coils 11 to 13, with the threshold current Ith, and the switching elements 211 to 216, 311 to 316 and the free wheel diode. Whether all the phases of the upper arm elements are turned on in the first inverter 20 or the second inverter 30 to be neutralized so that the maximum phase current Imax flows in the direction of smaller conduction loss between 221 to 226 and 321 to 326 Select whether to turn on all phases of the lower arm element.
Thereby, according to the maximum phase current Imax, the arm to be fixed on can be appropriately selected.

The threshold current Ith is variable according to the temperature of the first inverter 20 or the second inverter 30 that is neutralized. Thereby, according to inverter temperature T1, T2, the arm to fix on can be selected appropriately.
In the present embodiment, the freewheeling diodes 221 to 226 and 321 to 326 correspond to “refluxing elements”.

(Other embodiments)
(A) Phase current In the said embodiment, a phase current is estimated based on the current command value of each phase. In other embodiments, in other embodiments, the phase current may be the current command value itself.
In another embodiment, as illustrated in FIG. 7, a current detection unit 50 that detects the currents of the coils 11 to 13 may be provided, and the phase current may be calculated based on the detected current value. In FIG. 7, the current detection element of the current detection unit 50 is provided in each phase. However, the current detection element 50 is provided in one or two of the three phases, and the current of the phase in which the current detection element is not provided is obtained by calculation. May be. Moreover, in FIG. 7, the current detection part 50 is provided in the 1st inverter 20 side of the coils 11-13. In other embodiment, you may provide a current detection part in any location which can detect a phase current, such as the 2nd inverter 30 side of the coils 11-13. In FIG. 7, the same reference numerals are given to substantially the same components as those in the first embodiment, and description thereof is omitted.

(A) Inverter temperature In the said embodiment, 1st inverter temperature and 2nd inverter temperature are estimated based on a phase current etc. FIG. In another embodiment, as illustrated in FIG. 7, the temperature detection elements 231 to 236 and 331 to 336 may be provided for each of the switching elements 211 to 216 and 311 to 316. In this case, a calculated value such as an average value of element temperatures based on the detection values of the temperature detection elements 231 to 236 is set as the first inverter temperature T1. In addition, a calculated value such as an average value of element temperatures based on the detection values of the temperature detection elements 331 to 336 is set as the second inverter temperature T2. In other embodiments, the temperature detection element is not necessarily provided for each switching element, and one or more temperature detection elements may be provided for each inverter. For example, one each for the upper arm element and the lower arm element may be provided.
In the above embodiment, the threshold current is made variable according to the temperature of the inverter that is neutralized. In another embodiment, the threshold current may be a predetermined value regardless of the inverter temperature. In this case, the inverter temperature need not be estimated or detected.

(C) Switching element, reflux element In the above embodiment, an IGBT is used as the switching element. In other embodiments, a switching element other than an IGBT such as a MOSFET (metal oxide semiconductor field effect transistor) may be used. When a MOSFET is used as the switching element, a parasitic diode may be used as the reflux element. The reflux element may be built in the switching element or may be externally attached.

  In the above embodiment, the IGBT is used as the switching element, and the loss of the diode is small in the region where the current is smaller than the threshold current, and the loss of the IGBT is small in the region where the current is larger than the threshold current. In other embodiments, depending on the characteristics of the element used, the loss of the return element may be small in a region where the current is small, and the loss of the switching element may be small in a region where the current is large. In this case, the arm to be turned on may be reversed from that in the above embodiment so that the maximum phase current flows through the element with the smaller conduction loss.

(D) First voltage source, second voltage source In the above embodiment, lithium ion batteries and the like are exemplified as the first voltage source and the second voltage source. In other embodiments, the first voltage source and the second voltage source may be lead storage batteries other than lithium ion batteries, fuel cells, and the like. Further, the first voltage source and the second voltage source may be of the same type and characteristics, or may be different types and characteristics. One of the first voltage source and the second voltage source may be a capacitor such as an electric double layer capacitor or a lithium ion capacitor. One of the first voltage source and the second voltage source may be a generator that is driven by a driving source such as an engine to generate electric power.

(E) Rotating electric machine In the above embodiment, the rotating electric machine is a motor generator. In another embodiment, the rotating electrical machine may be an electric motor that does not have a function of a generator, or may be a generator that does not have a function of an electric motor. Further, the rotating electrical machine of the above embodiment has three phases. In other embodiments, the rotating electrical machine may have four or more phases. In the above embodiment, the rotating electrical machine drive system is not connected to the ground. However, in other embodiments, the rotating electrical machine drive system may be connected to the ground.

In the above embodiment, the rotating electrical machine is a main motor of an electric vehicle. In another embodiment, the rotating electrical machine is not limited to the main motor, but may be a so-called ISG (Integrated Starter Generator) having both a starter function and an alternator function, or an auxiliary motor. Moreover, you may apply a power converter device to apparatuses other than a vehicle.
As mentioned above, this invention is not limited to the said embodiment at all, In the range which does not deviate from the meaning of invention, it can implement with a various form.

DESCRIPTION OF SYMBOLS 1 ... Rotating electrical machine drive system 10 ... Motor generator (rotating electrical machine)
11-13 ... Coil (winding)
DESCRIPTION OF SYMBOLS 15 ... Power converter 20 ... 1st inverter 30 ... 2nd inverter 211-213, 311-313 ... Upper arm element 214-216, 314-316 ... Lower arm element 41 ...・ First battery (first voltage source)
42 ... Second battery (second voltage source)
60 ... Control unit

Claims (3)

A power converter (1) for converting electric power of a rotating electrical machine (10) having windings (11 to 13) of a plurality of phases,
A first inverter (20) connected to one end (111, 121, 131) of the winding and a first voltage source (41);
A second inverter (30) connected to the other end (112, 122, 132) of the winding and a second voltage source (42);
A control unit (60) for controlling the first inverter and the second inverter;
With
The first inverter and the second inverter are respectively an upper arm element (211 to 213, 311 to 313) connected to a high potential side or a lower arm element (214) connected to a low potential side of the upper arm element. 216, 314 to 316), which can be energized from the high potential side to the low potential side when turned on, and in parallel with each of the switching elements Having reflux elements (221-226, 321-326) that are connected and allow energization from the low potential side to the high potential side;
One of the first inverter and the second inverter is neutralized by turning on all phases of the upper arm element or all phases of the lower arm element, and the other of the first inverter and the second inverter is In the one-side drive mode that is controlled according to the drive request of the rotating electrical machine,
The controller is
In the first inverter or the second inverter that is neutralized, whether to turn on all the phases of the upper arm element or all the phases of the lower arm element depends on the current supplied to the winding. The power converter characterized by selecting according to. When the current value at which the magnitude of conduction loss is switched between the switching element and the reflux element is a threshold current,
The control unit compares the threshold current with a maximum phase current that is a phase current having the largest absolute value of the current passed through the winding, and has a smaller conduction loss between the switching element and the return element. In the first inverter or the second inverter that is neutralized, whether to turn on all phases of the upper arm element or turn on all phases of the lower arm element so that the maximum phase current flows in The power converter according to claim 1, wherein the power converter is selected.   The power converter according to claim 2, wherein the threshold current is variable according to a temperature of the first inverter or the second inverter that is neutralized.

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