JP2022179964A - Power conversion device - Google Patents

Abstract

To effectively use low loss elements in an H bridge motor drive system obtained by combining switching elements with different loss characteristics.SOLUTION: A first inverter is connected in parallel with a DC power supply and comprises a plurality of first switching elements for every phase of a rotary electric machine. A second inverter is connected in parallel with the DC power supply and comprises a plurality of second switching elements for every phase of the rotary electric machine. A control device controls the first and second inverters. The plurality of first switching elements and the plurality of second switching elements have mutually different loss characteristics. When the switching elements with smaller loss are defined as low loss elements, and the switching elements with larger loss are defined as high loss elements, the control device controls the first and second inverters so that the number of times of switching of one of the first and second inverters corresponding to the inverters on a side of using the low loss elements becomes more than the number of times of switching of the other of the first and second inverters corresponding to the inverters on a side of using the low loss elements.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to power converters.

Patent Literature 1 discloses an open winding system for driving a three-phase induction motor or the like. The open winding system includes first and second inverters for converting DC power of a DC power supply into AC power, and an open winding connected between AC output terminals of the first inverter and the second inverter. ing. The controller of the open winding system controls the switching elements so that the losses of the switching elements of the first and second inverters become equal.

JP 2017-093077 A

In a power conversion device (for convenience, also referred to as "H bridge motor drive system") having a configuration in which each phase coil (winding) is driven by an H bridge inverter like the open winding system described in Patent Document 1, the cost Considering the balance between efficiency and efficiency, it is conceivable to mix and use switching elements with different loss characteristics. When such a configuration is adopted, it is difficult to effectively use up the switching elements by controlling the switching elements so that the losses of the switching elements of the first and second inverters are equal.

The present disclosure has been made in view of the problems described above, and aims to enable effective use of low-loss elements in an H-bridge motor drive system that combines switching elements with different loss characteristics.

A power conversion device according to the present disclosure converts power supplied from a DC power supply to an open-winding rotating electrical machine having multi-phase coils, and includes a first inverter, a second inverter, a control a device;
The first inverter is connected in parallel with the DC power supply, and can open and close between the first high potential point and one end of the coil and between the one end of the coil and the first low potential point for each phase of the rotating electric machine. a plurality of first switching elements. The second inverter is connected in parallel with the DC power supply, and for each phase of the rotating electric machine, between the second high potential point and the other end of the coil, and between the other end of the coil and the second low potential point. It includes a plurality of second switching elements that can be opened and closed. A controller controls the first and second inverters.
The plurality of first switching elements and the plurality of second switching elements are configured to have different loss characteristics.
Among the plurality of first switching elements and the plurality of second switching elements, the one with the smaller loss is referred to as the low-loss element, and the one with the larger loss is referred to as the high-loss element. The number of switching times of one of the first and second inverters corresponding to the inverter on the side is greater than the number of switching times of the other of the first and second inverters corresponding to the inverter on the side using the high-loss element 2 to control the inverter.

The current flowing through each of the multi-phase coils is positive when flowing from the first inverter side to the second inverter side. The control device may include a control signal generation unit that generates a control signal for each of the plurality of first switching elements and the plurality of second switching elements for each phase of the plurality of phases. Then, when the fundamental modulated wave of the voltage command for each phase based on the drive command for the rotating electric machine is 0 or more, the control signal generator generates the fundamental modulated wave and the first carrier signal that fluctuates between 0 and 1. While generating control signals for the first switching elements that form the upper arm and the lower arm of the first inverter, control signals for the second switching elements that form the upper arm and the lower arm of the second inverter are generated respectively. When the fundamental modulated wave is turned off and on and the fundamental modulated wave is less than 0, the first corrected modulated wave obtained by adding 1 to the fundamental modulated wave is compared with the first carrier signal to compare the upper arm and the lower arm of the first inverter. may be generated to turn on and off the control signals for the second switching elements forming the upper arm and the lower arm of the second inverter, respectively, while generating the control signals for the first switching elements forming the respective .

The current flowing through each of the multi-phase coils is positive when flowing from the first inverter side to the second inverter side. The control device may include a control signal generation unit that generates a control signal for each of the plurality of first switching elements and the plurality of second switching elements for each phase of the plurality of phases. Then, when the fundamental modulated wave of the voltage command for each phase based on the drive command for the rotating electric machine is less than 0, the control signal generator generates the fundamental modulated wave and the second carrier signal that fluctuates between -1 and 0. are compared to generate control signals for the second switching elements that form the upper arm and the lower arm of the second inverter, respectively, while generating control signals for the first switching elements that form the upper arm and the lower arm of the first inverter. When the fundamental modulated wave is 0 or more, the second corrected modulated wave obtained by adding -1 to the fundamental modulated wave is compared with the second carrier signal to compare the upper arm and the second carrier signal of the second inverter. The control signals for the first switching elements forming the upper and lower arms of the first inverter may be turned on and off while the control signals for the second switching elements forming the lower arms are generated.

The power conversion device may further include a switch arranged between the first inverter and the second inverter for switching between a conducting state and a blocking state of current. The plurality of first switching elements included in the first inverter may be low-loss elements.

The plurality of first switching elements and the plurality of second switching elements may be configured to have different loss characteristics due to differences in materials.

The plurality of first switching elements and the plurality of second switching elements may be configured to have different loss characteristics due to the difference in chip area.

According to the power conversion device according to the present disclosure, in an H-bridge motor drive system in which switching elements with different loss characteristics are combined for each inverter, one of the first and second inverters corresponding to the inverter using the low-loss element The first and second inverters are controlled such that the number of switching times is greater than that of the other of the first and second inverters corresponding to the inverter using the high-loss element. As a result, the inverter loss can be reduced by effectively utilizing the low-loss elements.

1 is a diagram schematically showing a configuration of a power converter according to Embodiment 1; FIG. Time chart (A) showing a control signal generation method in general switching control (comparative example) and time chart (B) showing a control signal generation method in characteristic switching control according to Embodiment 1 is. FIG. 7 is a diagram summarizing the relationship between modulated waves and on/off states of connection points U1 and U2 in a comparative example. 4 is a flow chart showing a procedure for generating a control signal by a control signal generator according to Embodiment 1; 4 is a time chart showing a method of generating a control signal when increasing the number of times of switching of a second switching element SW2 on the second inverter side; FIG. 3 is a diagram for explaining the effect of the first embodiment with respect to the comparative example shown in FIG. 2(A); FIG. 6 is a diagram schematically showing the configuration of a power converter according to Embodiment 2; It is a figure which shows the control state of the power converter device at the time of a Y-connection drive. FIG. 10 is a diagram schematically showing the configuration of a power converter according to a first modified example of the second embodiment; FIG. 10 is a diagram schematically showing the configuration of a power converter according to a second modification of the second embodiment; It is a figure which shows roughly the structure of the power converter device applied to the rotary electric machine of five phases.

In each embodiment described below, the same reference numerals are given to the elements common to each drawing, and overlapping descriptions are omitted or simplified. In addition, when referring to numbers such as the number, quantity, amount, range, etc. of each element in the embodiments shown below, unless otherwise specified or clearly specified in principle, the reference The technical idea according to the present disclosure is not limited to the number. In addition, structures, steps, and the like described in the embodiments shown below are not necessarily essential to the technical concept of the present disclosure, unless otherwise specified or clearly specified in principle.

1. Embodiment 1
1-1. Configuration of Power Converter FIG. 1 is a diagram schematically showing a configuration of a power converter 100 according to Embodiment 1. As shown in FIG. FIG. 1 shows an electric motor 1 , a DC power supply 2 (for example, a battery), and a smoothing capacitor 3 together with a power conversion device 100 . The power conversion device 100 is configured to convert power supplied from the DC power supply 2 toward the electric motor 1 .

The electric motor 1 is mounted, for example, in an electric vehicle such as an electric vehicle or a hybrid vehicle, and generates torque for driving drive wheels (not shown) of the electric vehicle. The electric motor 1 is an example of a "rotating electric machine" according to the present disclosure. The rotating electric machine is not limited to an electric motor, and may be, for example, a generator, or a motor generator having a function as an electric motor and a function as a generator.

The electric motor 1 is a three-phase open-winding electric motor, and has three coils 4 (a U-phase coil 4U, a V-phase coil 4V, and a W-phase coil 4W). That is, the electric motor 1 has a configuration in which both ends of the coils 4 of each phase are open.

The power conversion device 100 includes a first inverter 10 , a second inverter 30 and a control device 60 . The first inverter 10 and the second inverter 30 are each connected in parallel with the DC power supply 2 . More specifically, the first inverter 10 is arranged closer to the DC power supply 2 than the second inverter 30 is. The smoothing capacitor 3 described above is connected between the DC power supply 2 and the first inverter 10 .

1-1-1. First and Second Inverters The first inverter 10 is a three-phase inverter that switches energization of the coils 4 of each phase. The first inverter 10 is connected between a first high potential point H1 of the first inverter 10 and one end of the coil 4 and between one end of the coil 4 and a first low potential point of the first inverter 10 for each phase of the electric motor 1 . A plurality of first switching elements 12, 14, 16, 18, 20, and 22 that can be opened/closed (on/off) with L1 are provided. In this embodiment, when the first switching elements 12, 14, 16, 18, 20, and 22 are collectively referred to as "first switching element SW1".

More specifically, the first inverter 10 includes a first switching element 12 provided between the first high potential point H1 and the connection point U1, and a first switching element 12 provided between the connection point U1 and the first switching element 12 corresponding to the U-phase coil 4U. and a first switching element 14 provided between the low potential point L1. One end of a U-phase coil 4U is connected to a connection point U1 between these U-phase first switching elements 12 and .

In addition, the first inverter 10 includes a first switching element 16 provided between the first high potential point H1 and the connection point V1, and a first switching element 16 provided between the connection point V1 and the first low potential point corresponding to the V-phase coil 4V. and a first switching element 18 provided between L1. One end of a V-phase coil 4V is connected to a connection point V1 between these V-phase first switching elements 16 and 18 .

Further, the first inverter 10 includes a first switching element 20 provided between the first high potential point H1 and the connection point W1, and a first switching element 20 provided between the connection point W1 and the first low potential point corresponding to the W-phase coil 4W. and a first switching element 22 provided between L1. One end of a W-phase coil 4W is connected to a connection point W1 between the W-phase first switching elements 20 and 22. As shown in FIG.

Like the first inverter 10, the second inverter 30 is also a three-phase inverter that switches energization of the coils 4 of each phase. The second inverter 30 is connected between the second high potential point H2 of the second inverter 30 and the other end of the coil 4 and between the other end of the coil 4 and the second low potential point of the second inverter 30 for each phase of the electric motor 1 . A plurality of second switching elements 32, 34, 36, 38, 40, and 42 are provided which can be opened/closed (on/off) with the potential point L2. In the present embodiment, the second switching elements 32, 34, 36, 38, 40, and 42 are collectively referred to as "second switching element SW2".

More specifically, the second inverter 30 includes a second switching element 32 provided between the second high potential point H2 and the connection point U2 and a second switching element 32 provided between the connection point U2 and the second switching element 32 corresponding to the U-phase coil 4U. and a second switching element 34 provided between the low potential point L2. A connection point U2 between the U-phase second switching elements 32 and 34 is connected to the other end of the U-phase coil 4U.

The second inverter 30 also includes a second switching element 36 provided between the second high potential point H2 and the connection point V2, and a second switching element 36 provided between the connection point V2 and the second low potential point corresponding to the V-phase coil 4V. and a second switching element 38 provided between L2. A connection point V2 between these V-phase second switching elements 36 and 38 is connected to the other end of the V-phase coil 4V.

Further, the second inverter 30 includes a second switching element 40 provided between the second high potential point H2 and the connection point W2 corresponding to the W-phase coil 4W, and a second switching element 40 provided between the connection point W2 and the second low potential point. and a second switching element 42 provided between L2. A connection point W2 between the W-phase second switching elements 40 and 42 is connected to the other end of the V-phase coil 4W.

A control device 60 controls on/off of the first switching element SW1 and the second switching element SW2. When the first switching element SW1 and the second switching element SW2 are turned on, conduction from the high potential side to the low potential side is allowed, and when turned off, the conduction is interrupted.

A first high potential point H1 of the first inverter 10 is connected to the positive electrode of the DC power supply 2 . A high potential side connection line 50 connects between the first high potential point H1 and the second high potential point H2 of the second inverter 30 . Also, the first low potential point L1 of the first inverter 10 is connected to the negative electrode of the DC power supply 2 . A low potential side connection line 52 connects between the first low potential point L1 and the second low potential point L2 of the second inverter 30 .

As described above, the first inverter 10 and the second inverter 30 are connected in an H-bridge configuration in which each phase of the first and second inverters 10 and 30 is connected via each phase of the electric motor 1 (that is, H configured as a bridge inverter). In the following description, it is assumed that the current flowing through each of the three-phase coils 4 is positive when flowing from the first inverter 10 side to the second inverter 30 side. In this configuration, depending on the switching states of the first inverter 10 and the second inverter 30, the voltage across the coil 4 can be the positive power supply voltage Vdc, the negative power supply voltage Vdc, or zero.

1-1-2. Loss characteristics of the first and second switching elements In the present embodiment, the first switching element SW1 on the first inverter 10 side and the second switching element SW2 on the second inverter 30 side have different loss characteristics due to the difference in material. is configured to have

Specifically, the first switching element SW1 is, as an example, an insulated gate bipolar transistor (IGBT) with a diode (freewheeling diode) 24 . The material of the IGBT is Si (silicon), for example. Diode 24 allows conduction from the low potential side to the high potential side. On the other hand, the second switching element SW2 is, for example, a metal oxide semiconductor field effect transistor (MOSFET) made of SiC (silicon carbide). The MOSFET includes a diode (parasitic diode) 44 . In this embodiment, the first switching element SW1 and the second switching element SW2 are configured to have different loss characteristics by mixing the Si IGBT and the SiC MOSFET in inverter units. It is

1-1-3. Control Device The control device 60 controls the first and second inverters 10, 30 configured as described above. The control device 60 is connected to the first inverter 10 and the second inverter 30 as well as to a current detector 62, a voltage detector 64, and a rotation angle sensor (not shown). The control device 60 includes a CPU (Central Processing Unit), a memory, and a non-volatile storage unit, and performs various kinds of arithmetic processing. Arithmetic processing in the control device 60 may be realized by software processing by executing a program stored in advance by the CPU, or may be realized by hardware processing by a dedicated electronic circuit.

The current detector 62 includes, for example, a current detection element such as a Hall element for each phase of the electric motor 1 and detects the current flowing through each coil 4 . The voltage detector 64 detects the power supply voltage (DC voltage across the smoothing capacitor 3) Vdc. Further, the rotational angle sensor detects a rotational electrical angle θ of the output shaft of the electric motor 1 .

The control device 60 includes a control signal generator 60a. In order to control the first and second inverters 10 and 30, the control signal generator 60a generates a control signal (PWM (Pulse Width Modulation) signal) for controlling on/off of the first switching element SW1 and the second switching element SW2. Generate. The PWM signal is generated for each phase of the electric motor 1 based on the electrical rotation angle θ of the electric motor 1, the current value of each phase, and the voltage command value of each phase generated based on the torque command value. Then, the control device 60 generates and outputs a gate signal for controlling on/off of the first switching element SW1 and the second switching element SW2 according to the generated PWM signal. By turning on and off the first switching element SW1 and the second switching element SW2 according to the PWM signal, the DC power from the DC power supply 2 is converted into AC power and supplied to the electric motor 1 . More specifically, a voltage is applied to the coil 4 of each phase. Thereby, the electric motor 1 is driven.

As described above, the power conversion device 100 of this embodiment has a configuration in which the coils 4 of the respective phases of the electric motor 1 are driven by the H-bridge inverter (H-bridge motor drive system). In such a configuration, by appropriately controlling the switching of each phase of the first and second inverters 10 and 30, the voltage applied to each phase of the electric motor 1 can be appropriately controlled to drive the electric motor 1. can be done.

1-2. Characteristic Portion of Switching Control Here, of the first switching element SW1 and the second switching element SW2, the one with the smaller loss is referred to as the "low loss element", and the one with the larger loss is referred to as the "high loss element". The losses here are typically switching losses and conduction losses.

The switching control of the first switching element SW1 and the second switching element SW2 in this embodiment has the following features. That is, the control device 60 controls the number of times of switching of one of the first and second inverters 10 and 30 corresponding to the inverter using the low-loss element to switch between the first and second inverters corresponding to the inverter using the high-loss element. The first and second inverters 10, 30 are controlled so that the number of switching times of the other inverters 10, 30 is greater.

In this embodiment, as will be described later with reference to FIG. 4, it is not uniform which of the first switching element SW1 and the second switching element SW2 corresponds to the low-loss element. Different examples are assumed according to the amount of current in each of the switching elements SW1 and SW2 that changes according to .

FIG. 2A is a time chart showing a method of generating a control signal (PMW signal) in general switching control (comparative example), and FIG. 4 is a time chart showing a control signal (PWM signal) generation method in switching control; In FIG. 2, the method of generating the PWM signal will be described by taking the U-phase as an example, but the same applies to the other V-phase and W-phase. Also, the comparative example is the same as the power converter 100 of the first embodiment in terms of the circuit configuration of the power converter, and is different from the first embodiment in the method of generating the PWM signal.

First, a comparative example will be described with reference to FIG. A U-phase modulated wave Vu (a sine wave as an example) shown in FIG. It is what you get. The first carrier signal C1 and the second carrier signal C2 (carrier waves) are, for example, triangular waves. The first carrier signal C1 is generated to vary from 0 to 1, and the second carrier signal C2 is generated to vary from -1 to 0.

The control signal generator in the comparative example compares the U-phase modulated wave Vu and the first carrier signal C1 to generate PWM signals for the first switching elements 12 and 14 on the first inverter 10 side. Specifically, when the U-phase modulated wave Vu is greater than the first carrier signal C1, the control signal generator turns on the connection point U1 (see FIG. 1) of the first inverter 10 (that is, configures the upper arm). The first switching element 12 that is connected to the lower arm is turned on, and the first switching element 14 that constitutes the lower arm is turned off). On the other hand, when the U-phase modulated wave Vu is smaller than the first carrier signal C1, the control signal generator turns off the connection point U1 (that is, turns off the first switching element 12 constituting the upper arm and turns off the lower arm. The first switching element 14 is turned on).

Also, the control signal generator in the comparative example compares the U-phase modulated wave Vu and the second carrier signal C2 to generate PWM signals for the second switching elements 32 and 34 on the second inverter 30 side. Specifically, when the U-phase modulated wave Vu is greater than the second carrier signal C2, the control signal generator turns off the connection point U2 (see FIG. 1) of the second inverter 30 (that is, configures the upper arm). The second switching element 32 that is connected to the lower arm is turned off, and the second switching element 34 that constitutes the lower arm is turned on). On the other hand, when the U-phase modulated wave Vu is smaller than the second carrier signal C2, the control signal generator turns on the connection point U2 (that is, turns on the second switching element 32 that constitutes the upper arm and turns on the lower arm. The second switching element 34 is turned off).

FIG. 3 is a diagram summarizing the relationship between the modulated wave and the ON/OFF states of the connection points U1 and U2 in the comparative example. As described above with reference to FIG. 2A, according to the comparative example, when the U-phase modulated wave Vu is greater than the first carrier signal C1, the connection point U1 is turned on and the connection point U2 is turned off. It is said that When the U-phase modulated wave Vu is between the first carrier signal C1 and the second carrier signal C2, the connection points U1 and U2 are both turned off. Further, when the U-phase modulated wave Vu is smaller than the second carrier signal C2, the connection point U1 is turned off and the connection point U2 is turned on.

According to the comparative example shown in FIG. 2A described above, the first and second inverters 10 and 30 are controlled so that the number of switching times of the first inverter 10 and the second inverter 30 are equal.

Next, the operation of the control signal generator 60a of this embodiment will be described with reference to FIG. 2(B). Here, a technique for increasing the number of switching times of the first inverter 10 more than that of the second inverter 30 will be described. In order to increase the number of times of switching of the first inverter 10, the control signal generator 60a controls the modulated wave (the U-phase modulated wave Vu and the 1 Correction modulated wave Vu_new1) is set. Specifically, when the U-phase modulated wave Vu (basic modulated wave of the voltage command) is 0 or more (solid line), the control signal generator 60a uses the U-phase modulated wave Vu (basic modulated wave) as it is. . On the other hand, when the U-phase modulated wave Vu (fundamental modulated wave) is less than 0 (dashed line), the first corrected modulated wave Vu_new1 obtained by adding 1 to the fundamental modulated wave is set.

Then, when the U-phase modulated wave Vu (fundamental modulated wave) is 0 or more (solid line), the control signal generator 60a controls the first switching element 12 that constitutes the upper arm and the lower arm on the first inverter 10 side. and 14 PWM signals are generated by comparing the U-phase modulated wave Vu and the first carrier signal C1, as in the comparative example. Further, when the fundamental modulated wave is 0 or more, the control signal generator 60a turns off the connection point U2 of the second inverter 30 (that is, turns off the second switching element 32 constituting the upper arm and turns off the lower arm). The second switching element 34 forming the arm is turned on).

On the other hand, when the U-phase modulated wave Vu (fundamental modulated wave) is less than 0 (dashed line), the control signal generator 60a compares the first corrected modulated wave Vu_new1 and the first carrier signal C1, and the first inverter A PWM signal is generated for the first switching elements 12 and 14 that respectively constitute the upper arm and the lower arm on the 10 side. Specifically, the control signal generator 60a turns on the connection point U1 when the first corrected modulated wave Vu_new1 is greater than the first carrier signal C1, and connects when the first corrected modulated wave Vu_new1 is smaller than the first carrier signal C1. Point U1 is turned off. Further, when the fundamental modulated wave is less than 0, the control signal generator 60a turns on the connection point U2 of the second inverter 30. FIG.

According to the PWM signal generation method described with reference to FIG. 2B, the number of switching times of the first inverter 10 is increased more than that of the second inverter 30 while the voltage applied to the electric motor 1 is the same as that of the comparative example. can be made More specifically, according to this method, when the U-phase modulated wave Vu (fundamental modulated wave) is less than 0 (broken line), the first correction is performed while the connection point U2 of the second inverter 30 is continuously turned on. By generating the PWM signal on the side of the first inverter 10 by comparing the modulated wave Vu_new1 and the first carrier signal C1, a voltage equivalent to that of the comparative example shown in FIG. 2A can be applied to the electric motor 1. Thus, according to this method, it is possible to easily generate a PWM signal in which the occurrence of switching is biased toward the first inverter 10 side.

Next, FIG. 4 is a flow chart showing a procedure for generating a control signal (PWM signal) by the control signal generator 60a according to the first embodiment.

In FIG. 4, the control signal generator 60a (control device 60) first extracts (obtains) the current operating point of the electric motor 1 in step S100. This operating point is specified by, for example, the torque and rotation speed of the electric motor 1 . After that, the process proceeds to step S102.

In step S102, the control signal generator 60a determines which of the first inverter 10 and the second inverter 30 the number of times of switching should be increased. Specifically, which inverter to increase the number of times of switching (in other words, which inverter to increase the loss) is determined, for example, by each switching element SW1 that changes according to the current operating point of the electric motor 1 , SW2. More specifically, in a current amount range in which the first switching element SW1 corresponds to a low-loss element, the number of times of switching of the first switching element SW1 is increased and the number of times of switching of the second switching element SW2 is increased by the processing of steps S104 to S114 below. Switching times are reduced. On the other hand, in the current amount range in which the second switching element SW2 corresponds to the low loss element, the number of switching times of the second switching element SW2 is increased by the processing of steps S116 to S126 below, and the number of switching times of the first switching element SW1 is reduced.

If it is determined to increase the number of switching times of the first switching element SW1 (step S102; Yes), the control signal generator 60a checks in step S104 whether or not the modulated wave Vx of the current command is 0 or more. judge. “Modulated wave Vx” indicates an x-phase modulated wave, and x takes three variables of U, V, and W in a three-phase example. The processes of steps S106 and S108 following step S104 and the processes of steps S110 to S114 correspond to the example shown in FIG. 2B.

If the modulated wave Vx (corresponding to the “basic modulated wave” according to the present disclosure) is 0 or more (the solid line in FIG. 2B) in step S104, the control signal generation unit 60a generates the modulated wave Vx in step S106. Vx is compared with the first carrier signal C1 to generate the control signal for the first inverter 10 (ie, the PWM signal described above). In subsequent step S108, the control signal generator 60a sets the x-phase connection point X2 (U2, V2, and W2) of the second inverter 30 to off.

On the other hand, if the modulated wave Vx (fundamental modulated wave) is less than 0 in step S104 (broken line in FIG. 2B), the control signal generator 60a sets the first corrected modulated wave Vx_new1 in step S110. do. The first corrected modulated wave Vx_new1 is obtained by adding 1 to the modulated wave Vx (basic modulated wave).

In step S112 following step S110, the control signal generator 60a compares the first corrected modulated wave Vx_new1 with the first carrier signal C1 to generate a control signal (PWM signal) for the first inverter 10. FIG. In subsequent step S114, the control signal generator 60a sets the x-phase connection point X2 of the second inverter 30 to ON.

If it is determined to increase the number of times of switching of the second switching element SW2 (step S102; No), the control signal generator 60a determines whether or not the modulated wave Vx is less than 0 in step S116. do. The processing of steps S118 and S120 following step S116 and the processing of steps S122 to S126 will be described with reference to FIG.

FIG. 5 is a time chart showing a method of generating a control signal (PWM signal) when increasing the number of times of switching of the second switching element SW2 on the second inverter 30 side. In the method shown in FIG. 5, in order to increase the number of switching times of the second inverter 30, the modulated waves (modulated wave Vx and second corrected modulated wave Vx_new2) have an amplitude range of -1 to 0, as shown in FIG. set to fit within

If the modulated wave Vx (fundamental modulated wave) is less than 0 in step S116 (the solid line in FIG. 5), the control signal generator 60a converts the modulated wave Vx (fundamental modulated wave) to the second carrier signal in step S118. A control signal (PWM signal) for the second inverter 30 is generated in comparison with C2. More specifically, as shown in FIG. 5, when the modulated wave Vx is greater than the second carrier signal C2, the control signal generator 60a turns off the connection point X2 of the second inverter 30 (that is, turns off the upper arm). The second switching element SW2 forming the lower arm is turned off, and the second switching element SW2 forming the lower arm is turned on). On the other hand, when the modulated wave Vx is smaller than the second carrier signal C2, the control signal generation unit 60a turns on the connection point X2 (that is, turns on the second switching element SW2 that constitutes the upper arm and constitutes the lower arm). turn off the second switching element SW2).

In subsequent step S120, the control signal generator 60a sets the x-phase connection point X1 (U1, V1, and W1) of the first inverter 10 to off.

On the other hand, if the modulated wave Vx (basic modulated wave) is 0 or more in step S116 (broken line in FIG. 5), the control signal generator 60a sets the second corrected modulated wave Vx_new2 in step S122. The second corrected modulated wave Vx_new2 is obtained by adding -1 to the modulated wave Vx (basic modulated wave).

In step S124 following step S122, the control signal generator 60a compares the second corrected modulated wave Vx_new2 with the second carrier signal C2 to generate a control signal (PWM signal) for the second inverter 30. FIG. More specifically, as shown in FIG. 5, when the second corrected modulated wave Vx_new2 is greater than the second carrier signal C2, the control signal generator 60a turns off the connection point X2. On the other hand, when the second corrected modulated wave Vx_new2 is smaller than the second carrier signal C2, the control signal generator 60a turns on the connection point X2.

In subsequent step S126, the control signal generator 60a sets the x-phase connection point X1 of the first inverter 10 to ON.

In addition, according to the PWM signal generation method (steps S116 to S126) described with reference to FIG. 30 can be increased over that of the first inverter 10). More specifically, according to this method, when the modulated wave Vx (fundamental modulated wave) is 0 or more (broken line), the connection point X1 of the first inverter 10 is continuously turned on while the second corrected modulated wave By generating the PWM signal on the side of the second inverter 30 by comparing Vu_new2 and the second carrier signal C2, a voltage equivalent to that in the comparative example can be applied to the electric motor 1. FIG. Thus, according to this method, it is possible to easily generate a PWM signal in which the occurrence of switching is biased toward the second inverter 30 side.

1-3. Effect As described above, according to the power conversion device 100 according to the first embodiment, in the H-bridge motor drive system, switching elements having different loss characteristics are mixed and used for each inverter by utilizing the difference in materials. ing. The number of switching times of one of the first and second inverters 10 and 30 corresponding to the inverter using the low-loss element is the same as that of the first and second inverter 10 and 30 corresponding to the inverter using the high-loss element. The first and second inverters 10 and 30 are controlled so that the number of times of switching is greater than that of the other. As a result, the inverter loss (switching loss and conduction loss) can be reduced by making effective use of low-loss elements.

The effect of reducing the inverter loss will be described in more detail with reference to FIG. FIG. 6 is a diagram for explaining the effect of the first embodiment with respect to the comparative example shown in FIG. 2(A). An example of the effect shown in FIG. 6 shows a simulation result in an example in which the first switching element SW1 corresponds to a high-loss element and the second switching element SW2 corresponds to a low-loss element. The switching control of the present embodiment is control to concentrate (bias) the occurrence of switching on one inverter (second inverter 30 in this example) (that is, on the low-loss element side). Therefore, as shown in FIG. 6, the switching loss on the first inverter 10 side is greatly reduced compared to the comparative example due to the reduction in the number of switching times of the high-loss element (first switching element SW1). In addition, although the switching loss on the second inverter 30 side increases compared to the comparative example due to the concentration of switching, the amount of increase is kept low because it is on the low-loss element side. Also, the conduction loss of the second inverter 30 is reduced compared to the comparative example. As a result, the loss in the entire inverter was reduced by 14% compared to the comparative example. Further, even if the switching control of the present embodiment is performed, the voltage applied to the electric motor 1 is the same as that of the comparative example, so the loss of the electric motor 1 (motor loss) is the same. Therefore, according to the power converter 100 according to the present embodiment, the total loss in the H-bridge motor drive system including the loss of the electric motor 1 can be reduced.

As described above, according to the present embodiment, low-loss elements can be effectively used in an H-bridge motor drive system in which switching elements having different loss characteristics are combined. More specifically, the loss of the H-bridge motor drive system can be reduced by effectively utilizing the low-loss elements while reducing the use of the low-loss elements for cost reduction. This leads to an improvement in electric power consumption of an electric vehicle equipped with an H-bridge motor drive system.

1-4. Other Configuration Examples of Different Loss Characteristics In the first embodiment described above, the first switching element SW1 and the second switching element SW2 are configured to have different loss characteristics due to the difference in materials. However, instead of using such a difference in material, the "plurality of first switching elements" and the "plurality of second switching elements" according to the present disclosure have different loss characteristics due to the difference in chip area. It may be configured as

2. Embodiment 2
FIG. 7 is a diagram schematically showing the configuration of power converter 200 according to the second embodiment. The power conversion device 200 differs from the power conversion device 100 according to Embodiment 1 in the following points.

Specifically, the power conversion device 200 includes first and second inverters 210 and 230 instead of the first and second inverters 10 and 30 . In this embodiment, the first switching elements SW1 (212, 214, 216, 218, 220, and 222) on the first inverter 210 side are SiC MOSFETs, contrary to the example shown in FIG. The second switching elements SW2 (232, 234, 236, 238, 240, and 242) on the second inverter 230 side are Si IGBTs, contrary to the example shown in FIG.

Moreover, unlike the power conversion device 100 , the power conversion device 200 includes a switch 202 . The switch 202 is arranged on the high potential side connection line 50 . Switch 202 is turned on and off by controller 60 . The switch 202 is, for example, a semiconductor switch (IGBT as an example). Alternatively, switch 202 may be a mechanical switch such as, for example, a relay. As described above, the power conversion device 200 includes the switch 202 that is arranged between the first inverter 210 and the second inverter 230 and switches between the conducting state and the blocking state of the current.

According to the power conversion device 200 having the above-described configuration, by continuously turning on the switch 202, it is possible to perform open connection driving in the H-bridge configuration, as in the power conversion device 100 of the first embodiment. can. By similarly executing the processing of the flowchart shown in FIG. 4 for the power conversion device 200, it is possible to effectively utilize the low-loss elements and reduce the inverter loss (switching loss and conduction loss).

Further, according to the power conversion device 200, Y-connection driving can also be performed in a desired Y-connection driving region. FIG. 8 is a diagram showing the operating state of the power conversion device 200 during Y-connection driving. When performing Y-connection driving, the control device 60 keeps the switch 202 off. In addition, control device 60 continuously turns on second switching elements 232 , 236 , and 240 that form the upper arm of second inverter 230 , and second switching elements that form the lower arm of second inverter 230 . Each of the switching elements 234, 238, and 242 is kept off. Thereby, the second inverter 230 can be operated as a neutral point of each coil 4 of the electric motor 1 .

Moreover, in the power conversion device 200, a SiC MOSFET as a low-loss element is arranged on the first inverter 210 side. Therefore, by performing Y-connection driving in a drive region where the SiC MOSFET functions as a low-loss element, switching can be performed only by the low-loss element during Y-connection driving. This makes it possible to further reduce the inverter loss.

FIG. 9 is a diagram schematically showing the configuration of a power conversion device 300 according to a first modified example of the second embodiment. The power conversion device 300 differs from the power conversion device 200 according to the second embodiment in that a switch 302 is additionally provided.

Specifically, the switch 302 is arranged on the low potential side connection line 52 . Like the switch 202, the switch 302 is, for example, a semiconductor switch (IGBT as an example). Switch 302 is turned on and off by controller 60 . Note that the switch 302 also corresponds to an example of the "switch" according to the present disclosure.

In the power conversion device 300 having the switches 202 and 302 on both the high potential side and the low potential side, respectively, Y-connection driving can be performed by the following method, for example. That is, the control device 60 keeps the switches 202 and 302 off. In addition, control device 60 continuously turns off second switching elements 232 , 236 , and 240 that form the upper arm of second inverter 230 , and the second switching elements that form the lower arm of second inverter 230 . Each of the switching elements 234, 238, and 242 are kept on. Thereby, the second inverter 230 can be operated as a neutral point of each coil 4 of the electric motor 1 . Alternatively, the control device 60 continuously turns on the second switching elements 232, 236, and 240 constituting the upper arm, and turns on the second switching elements 234, 238, and 242 constituting the lower arm. may be operated as a neutral point of each coil 4 by continuously turning off .

FIG. 10 is a diagram schematically showing the configuration of a power conversion device 400 according to a second modification of the second embodiment. Power conversion device 400 differs from power conversion device 200 according to the second embodiment in that it includes switches 402 and 404 instead of switch 202 .

Specifically, the switches 402 and 404 are arranged on the high potential side connection line 50 and the low potential side connection line 52, respectively. These switches 402 and 404 are semiconductor switches, for example, and are configured to be able to control conduction/interruption of bidirectional current. Switches 402 and 404 are turned on and off by controller 60 . Such bidirectional switches 402 and 404 may be used as another example of a "switch" according to the present disclosure for enabling Y-connection driving.

3. Other Embodiments In the first and second embodiments described above, the power conversion device 100 and the like applied to the three-phase electric motor 1 have been described as an example. However, the "rotating electric machine" according to the present disclosure may be, for example, a five-phase rotating electric machine.

FIG. 11 is a diagram schematically showing the configuration of a power conversion device 500 applied to a five-phase rotating electric machine. The power conversion device 500 differs from the power conversion device 100 according to Embodiment 1 in the following points.

Specifically, FIG. 11 shows a five-phase electric motor 5 with open windings as an example of a five-phase rotary electric machine. This electric motor 5 has a five-phase coil 6 . The power conversion device 500 includes first and second inverters 510 and 520 instead of the first and second inverters 10 and 30 .

The first inverter 510 and the second inverter 520 are five-phase inverters that switch energization of the coils 6 of each phase. The first inverter 510 opens and closes (on/off) between the first high potential point H1 and one end of the coil 6 and between one end of the coil 6 and the first low potential point L1 for each phase of the electric motor 5. A possible plurality of first switching elements SW1 are provided. These first switching elements SW1 are, for example, IGBTs made of Si. The second inverter 520 opens and closes between the second high potential point H2 and the other end of the coil 6 and between the other end of the coil 6 and the second low potential point L2 for each phase of the electric motor 5 ( It has a plurality of second switching elements SW2 that can be turned on and off. These second switching elements SW2 are MOSFETs made of SiC, for example.

In addition, the "power converter" according to the present disclosure is not limited to the three-phase and five-phase examples described above, and may be similarly applied to a rotating electric machine having n-phase coils such as six-phase or nine-phase coils. In addition, each of the power converters 200, 300, and 400 described in the second embodiment may be modified so as to be similarly applied to a rotating electric machine having n-phase coils such as five-phase coils.

1, 5 electric motor (rotating electric machine)
2 DC power supply 3 Smoothing capacitors 4, 6 Electric motor coils 10, 210, 510 First inverter 12, 14, 16, 18, 20, 22, 212, 214, 216, 218, 220, 222, SW1 First switching element 24 , 44 diodes 30, 230, 520 second inverters 32, 34, 36, 38, 40, 42, 232, 234, 236, 238, 240, 242, SW2 second switching element 50 high potential side connection line 52 low potential side Connection line 60 Control device 60a Control signal generator 62 of control device Current detector 64 Voltage detector 100, 200, 300, 400, 500 Power conversion device 202, 302, 402, 404 Switch H1 First high potential point H2 Second High potential point L1 First low potential point L2 Second low potential point U1, V1, W1 Connection points U2, V2, W2 of one end of each phase coil to the first inverter Connection points of the other end of each phase coil to the second inverter connection point

Claims (6)

A power conversion device that converts power supplied from a DC power supply to an open-winding rotating electrical machine having multi-phase coils,
connected in parallel with the DC power supply, and capable of opening and closing between a first high potential point and one end of the coil and between one end of the coil and a first low potential point for each phase of the rotating electrical machine; a first inverter including a plurality of first switching elements;
connected in parallel with the DC power supply, and opens and closes between a second high potential point and the other end of the coil and between the other end of the coil and a second low potential point for each phase of the rotating electrical machine; a second inverter including a plurality of possible second switching elements;
a control device that controls the first and second inverters;
with
The plurality of first switching elements and the plurality of second switching elements are configured to have different loss characteristics,
When one of the plurality of first switching elements and the plurality of second switching elements with a smaller loss is referred to as a low-loss element, and the one with a larger loss is referred to as a high-loss element, the control device controls the low-loss The number of switching times of one of the first and second inverters corresponding to the inverter on the side using the element is greater than the number of switching times of the other of the first and second inverters corresponding to the inverter on the side using the high-loss element. A power conversion device characterized by controlling the first and second inverters so that The direction of the current flowing through each of the coils of the plurality of phases is positive when flowing from the side of the first inverter to the side of the second inverter,
The control device includes a control signal generator that generates a control signal for each of the plurality of first switching elements and the plurality of second switching elements for each phase of the plurality of phases,
The control signal generator is
When the fundamental modulated wave of the voltage command for each phase based on the drive command for the rotating electric machine is 0 or more, the fundamental modulated wave is compared with a first carrier signal that fluctuates between 0 and 1, and the first While generating a control signal for a first switching element forming an upper arm and a lower arm of the inverter, turning off and on a control signal for a second switching element forming an upper arm and a lower arm of the second inverter, respectively. ,
When the fundamental modulated wave is less than 0, the first corrected modulated wave obtained by adding 1 to the fundamental modulated wave is compared with the first carrier signal to adjust the upper arm and the lower arm of the first inverter. 3. The control signal for the second switching elements forming the upper arm and the lower arm of the second inverter is turned on and off, respectively, while generating the control signals for the first switching elements forming the respective first switching elements. 2. The power conversion device according to 1. The direction of the current flowing through each of the coils of the plurality of phases is positive when flowing from the side of the first inverter to the side of the second inverter,
The control device includes a control signal generator that generates a control signal for each of the plurality of first switching elements and the plurality of second switching elements for each phase of the plurality of phases,
The control signal generator is
When the fundamental modulated wave of the voltage command for each phase based on the drive command for the rotating electric machine is less than 0, the fundamental modulated wave is compared with the second carrier signal that fluctuates between -1 and 0, and the Generating a control signal for a second switching element respectively forming the upper arm and the lower arm of the two inverters, and turning off and on the control signal for the first switching element forming the upper arm and the lower arm respectively of the first inverter. year,
When the fundamental modulated wave is equal to or greater than 0, the second corrected modulated wave obtained by adding -1 to the fundamental modulated wave is compared with the second carrier signal to obtain upper and lower arms of the second inverter. While generating a control signal for a second switching element that configures each of Item 1. The power converter according to item 1. The power conversion device further includes a switch disposed between the first inverter and the second inverter for switching between a conduction state and a cut-off state of current,
The power converter according to any one of claims 1 to 3, wherein the plurality of first switching elements included in the first inverter are the low-loss elements. The plurality of first switching elements and the plurality of second switching elements are configured to have different loss characteristics due to differences in materials. The power conversion device according to . The plurality of first switching elements and the plurality of second switching elements are configured to have different loss characteristics due to a difference in chip area. 1. The power converter according to 1.

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