Rotating electric machine control device and rotating electric machine control method

Abstract

To provide a control device of a rotary electric machine and a control method of a rotary electric machine capable of efficiently suppressing noise and switching loss due to switching of a switching element.SOLUTION: A control device of a rotary electric machine includes: a gate driving circuit 30 that adjusts a current flowing through gates of switching elements 42U to 44W constituting an inverter 40 to change a switching transition time of the switching elements 42U to 44W; and a control device 10 that controls the gate driving circuit 30 so that the switching transition time of each of the switching elements 42U to 44W of any phase and the switching elements 42U to 44W of another phase is shorter than the normal time, at the timing at which the variation in physical quantity caused by the switching of the switching elements 42U to 44W of any phase and the variation in physical quantity caused by the switching of the switching elements 42U to 44W of another phase different from any phase are cancelled each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for a rotating electric machine and a control method for a rotating electric machine. [Background technology]

[0002] In a three-phase synchronous motor (hereafter referred to as a "rotating electric machine"), the three-phase AC voltage applied to the windings of the U, V, and W phases is generated by switching switching elements such as MOSFETs (metal-oxide semiconductor field-effect transistors). However, switching elements generate noise when they are switched.

[0003] Noise caused by switching of a switching element is affected by the length of the transition time, which is the time it takes for the drain-source voltage of the switching element to reach a voltage amplitude in a rising state from 0, or the time it takes for the drain-source voltage to go from the voltage amplitude to 0. For example, when the switching element is switched quickly so as to shorten the transition time, the generation of noise is likely to become noticeable. In order to suppress noise caused by switching of the switching element, it is conceivable to switch the switching element so as to lengthen the transition time, but when the transition time is lengthened, there is a problem that the switching loss of the switching element becomes noticeable, leading to heat generation and increased power consumption of the switching element.

[0004] Non-Patent Document 1 proposes inverter switching control that suppresses fluctuations in common-mode voltage, which causes noise, by using space vector modulation to make the terminal voltages of two-phase windings rise and fall at the same timing, while also suppressing switching losses in switching elements. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Shota Hanioka, Masahiro Iezawa, Satoshi Ogasawara, Masatoshi Takemoto, Koji Orikawa, “Switching Control for Canceling Conduction Noise Between Phases in a Voltage-Type PWM Inverter”, Transactions of the Institute of Electrical Engineers of Japan, Vol. 140 No. 12, 2020, P920-928 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the invention disclosed in Non-Patent Document 1 generates voltages to be applied to the windings of a rotating electric machine based on voltage vectors that are 180 degrees out of phase with each other, so that the terminal voltages of the two-phase windings may rise at the same time, which may make it difficult to suppress both noise and switching loss.

[0007] The present invention has been created in view of the above problems, and has an object to provide a control device for a rotating electric machine and a control method for a rotating electric machine that can effectively suppress noise and switching loss caused by switching of switching elements. [Means for solving the problem]

[0008] In order to achieve the above object, a control device for a rotating electric machine according to the present invention includes a power conversion circuit (40) that outputs three-phase AC generated from power supplied from a DC power source (80) by switching a plurality of switching elements (42U to 44W) to a winding of a rotating electric machine (12), a gate drive circuit (30) that adjusts currents passed through gates of the plurality of switching elements (42U to 44W) to change a switching transition time of the plurality of switching elements (42U to 44W) to either a normal time or a shortened time that is shorter than the normal time, and and a switching control unit (10) that controls the switching timing of the switching elements (42U to 44W) of any one of the phases and the gate drive circuit (30) so that a transition time of each of the switching elements (42U to 44W) of any one of the phases and the switching elements (42U to 44W) of the other phases becomes the shortened time at a timing when a fluctuation in physical quantity caused by the switching of the switching elements (42U to 44W) of any one of the phases and a fluctuation in physical quantity caused by the switching of the switching elements (42U to 44W) of the other phase different from the any one of the phases are offset.

[0009] With this configuration, it is possible to obtain a control device for a rotating electric machine and a control method for a rotating electric machine that can effectively suppress noise and switching loss caused by switching of switching elements. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an example of a control device for a rotating electric machine, a rotating electric machine, and an inverter according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing an example of a configuration of a gate drive circuit. [Diagram 3] FIG. 2 is a block diagram showing an example of a specific configuration of a control device. [Figure 4] 4 is a flowchart showing an example of processing by the control device for a rotating electric machine according to the first embodiment of the present invention. [Diagram 5]3 is an explanatory diagram showing an example of a switching pattern of each phase and a fluctuation in neutral point voltage of the control device for a rotating electric machine according to the first embodiment of the present invention. FIG. [Figure 6] FIG. 1 is an explanatory diagram showing a mechanism of noise generation. [Figure 7] 1 is a table showing switching modes corresponding to voltage vectors of switching elements constituting an inverter and neutral point voltages of a motor. [Figure 8] FIG. 4 is a schematic diagram showing an example of a voltage command vector Ve. [Figure 9] FIG. 6(A) is an explanatory diagram showing an example of transition of a voltage vector of a switching element shown in FIG. 5, and FIG. 6(B) is an explanatory diagram showing a switching pattern of the transitioning voltage vector. [Figure 10] FIG. 11 is an explanatory diagram of a case where switching of a switching element is controlled by voltage vectors with a phase difference of 120 degrees. [Figure 11] FIG. 11 is an explanatory diagram showing an example of a switching pattern of each phase and fluctuations in neutral point voltage when a voltage vector is switched with a phase difference of 120 degrees. [Figure 12] 10 is a schematic diagram showing an example of the configuration of a rotating electric machine including two inverter systems according to a second embodiment of the present invention. FIG. [Figure 13] 1 is an explanatory diagram showing an example of changes in voltage vectors and inverter currents of two inverters, and changes in inverter currents of the entire circuit. FIG. [Figure 14] 5A is an explanatory diagram illustrating a case where the absolute value of the rate of change of the switching transition time of a switching element of phase A is different from the absolute value of the rate of change of the switching transition time of a switching element of phase B, which is different from phase A, at the time of switching overlap timing in FIG. 5 etc. of the first embodiment, and FIG. 5B is an explanatory diagram illustrating a case where the absolute value of the rate of change of the switching transition time of a switching element of phase A is the same as the absolute value of the rate of change of the switching transition time of a switching element of phase B, which is different from phase A, at the time of switching overlap timing in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [First embodiment] A first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a block diagram showing an example of a control device 10 for a rotating electric machine according to this embodiment, a motor 12 which is a rotating electric machine, and an inverter 40. The inverter 40 is a three-phase inverter that converts a DC voltage supplied from a DC power source 80 such as a battery into a three-phase AC voltage of, for example, U-phase, V-phase, and W-phase, and outputs the AC voltage to the motor 12. As shown in Fig. 1, a smoothing capacitor 82 is connected in parallel to the DC power source 80.

[0012] 1, the inverter 40 according to this embodiment includes switching elements 42U, 42V, 42W, 44U, 44V, and 44W such as MOSFETs or IGBTs (insulated gate bipolar transistors), and generates power to be supplied to the coils of the stator of the motor 12 by switching the switching elements 42U, 42V, 42W, 44U, 44V, and 44W on and off. For example, the switching elements 42U and 44U switch the power to be supplied to the U-phase coil, the switching elements 42V and 44V switch the power to be supplied to the V-phase coil, and the switching elements 42W and 44W switch the power to be supplied to the W-phase coil.

[0013] The drains of the switching elements 42U, 42V, and 42W, which are so-called upper arm switches, are connected to the positive electrode (+) of the DC power supply 80, and the sources of the switching elements 42U, 42V, and 42W are connected to the drains of the switching elements 44U, 44V, and 44W, which are so-called lower arm switches. Also, the sources of the switching elements 44U, 44V, and 44W are connected to the negative electrode (-) of the DC power supply 80.

[0014] A node 46U, at which the source of the switching element 42U and the drain of the switching element 44U are connected, is connected to a U-phase coil of the motor 12. As an example, when the switching element 42U is turned on and the switching element 44U is turned off, power from the DC power supply 80 is supplied to the U-phase coil of the motor 12 via the node 46U. At the same time, as an example, when the switching element 42W is turned off and the switching element 44W is turned on, the current flowing through the U-phase coil flows through the W-phase coil via the neutral point of the coil of the motor 12. The current flows to the negative pole (-) of the DC power supply 80 via the node 46W, at which the source of the switching element 42W and the drain of the switching element 44W are connected, and the switching element 44W. When the U-phase coil and the W-phase coil are energized, a magnetic field is generated in the U-phase coil and the W-phase coil.

[0015] A node 46V, at which the source of switching element 42V and the drain of switching element 44V are connected, is connected to the V-phase coil of motor 12. As an example, when switching element 42V is turned on and switching element 44V is turned off, power from DC power supply 80 is supplied to the V-phase coil of motor 12 via node 46V. At the same time, as an example, when switching element 42U is turned off and switching element 44U is turned on, the current flowing through the V-phase coil flows through the U-phase coil via the neutral point of the coil of motor 12. The current flows to the negative pole (-) of DC power supply 80 via node 46U and switching element 44U. When the V-phase coil and the U-phase coil are energized, a magnetic field is generated in the V-phase coil and the U-phase coil.

[0016] Also, as an example, when switching element 42W is turned on and switching element 44W is turned off, power from DC power supply 80 is supplied to the W-phase coil of motor 12 via node 46W. At the same time, as an example, when switching element 42V is turned off and switching element 44V is turned on, the current flowing through the W-phase coil flows through the V-phase coil via the neutral point of the coil of motor 12. The current flows to the negative pole (-) of DC power supply 80 via node 46V and switching element 44V. When the W-phase coil and the V-phase coil are energized, a magnetic field is generated in the W-phase coil and the V-phase coil.

[0017] As described above, by switching the switching elements 42U, 42V, 42W, 44U, 44V, and 44W (hereinafter abbreviated as "switching elements 42U to 44W") to switch the phase in which a magnetic field is generated in the coils of motor 12, a so-called rotating magnetic field that rotates a rotor (rotor) made of a permanent magnet or the like is generated in the coils of motor 12. In actual motor rotation control, a three-phase AC-like voltage is generated and applied to the coils of each phase of motor 12 by PWM (pulse width modulation) control that turns each of the switching elements 42U to 44W on and off in short increments.

[0018] As an example, when the switching elements 42U-44W are n-type MOSFETs, they are turned on by applying a gate waveform of a positive voltage to the gate. As shown in Fig. 1, in this embodiment, a gate drive circuit 30 that controls the current value of the gate waveform is connected to each of the switching elements 42U-44W. In addition, a control device 10 is connected to the gate drive circuit 30. The gate drive circuit 30 amplifies a gate signal input from the control device 10 to drive the switching elements 42U-44W, and applies a gate waveform obtained by adjusting the current value of the amplified gate signal by a variable resistor to the gate of each of the switching elements 42U-44W.

[0019] Connected to the control device 10 are a rotation angle sensor 24 that detects the rotation angle of the rotor of the motor 12, a voltage detection unit 26 that detects the power supply voltage, which is the potential difference between the positive and negative poles of the DC power supply 80, and a current detection unit 28 that detects phase currents, which are currents passed through the coils of the U, V, and W phases of the motor 12. The rotation angle sensor 24 is an incremental encoder or the like that can detect the rotation angle and rotation speed of the rotor.

[0020] The control device 10 includes a switching pattern selection unit 14A that generates a switching pattern for the switching elements 42U-44W by space vector modulation, which will be described later, based on the rotation angle of the rotor, the power supply voltage (input voltage), and the phase current, and that generates a modulation command to generate a gate signal for each of the switching elements 42U-44W based on the generated switching pattern.

[0021] The control device 10 also includes a SW speed command generating unit 14B that generates SW speed command values ​​for shortening transition times of switching of each of the switching elements of a certain phase and the switching elements of the other phases to shorter than normal times at switching timings 112A, 112B, etc., described later with reference to FIG. 5, at timings at which fluctuations in physical quantities caused by switching of the switching elements of a certain phase and fluctuations in physical quantities caused by switching of the switching elements of the other phases are offset based on the switching pattern (SW pattern) generated by the switching pattern selecting unit 14A, thereby speeding up the switching. As described later, the physical quantities generated by switching of the switching elements are, one, the neutral point voltage of the motor 12, and the other, the inverter current generated by the operation of the inverter. In this embodiment, specific values ​​of the normal time and the shortened time in the transition time are appropriately determined based on the specifications of the switching elements 42U to 44W, taking into consideration the switching loss of the switching elements 42U to 44W, noise generation during switching, and the like. Furthermore, the SW speed command generating unit 14B may generate a SW speed command value that is not only either the normal time or the reduced time, but also any transition time between the normal time and the reduced time.

[0022] The gate signal generated by the switching pattern selection unit 14A and the SW speed command value generated by the SW speed command generation unit 14B are each output to the aforementioned gate drive circuit 30, and the gate drive circuit 30 generates a gate waveform to be applied to the gate of each of the switching elements 42U to 44W based on the input gate signal and SW speed command value.

[0023] 2 is a block diagram showing an example of the configuration of the gate drive circuit 30. The gate drive circuit 30 includes a gate drive circuit 30UA that outputs the generated gate waveform to the gate of switching element 42U, a gate drive circuit 30VA that outputs the generated gate waveform to the gate of switching element 42V, a gate drive circuit 30WA that outputs the generated gate waveform to the gate of switching element 42W, a gate drive circuit 30UB that outputs the generated gate waveform to the gate of switching element 44U, a gate drive circuit 30VB that outputs the generated gate waveform to the gate of switching element 44V, and a gate drive circuit 30WB that outputs the generated gate waveform to the gate of switching element 44W.

[0024] Since each of the gate drive circuits 30UA to 30WB has a similar configuration, the configuration of the gate drive circuit 30UA will be described as an example.

[0025] As shown in FIG. 2, the gate drive circuit 30UA includes a SW speed control unit 32U that controls the operation unit 34U based on the SW speed command value output by the control device 10, and an operation unit 34U that changes the gate drive capability based on the control of the SW speed control unit 32U.

[0026] A gate signal is input to the operation unit 34U from the control device 10 via an amplifier 36U and a complementary MOS 38U, which is a type of inversion circuit. The gate signal input from the control device 10 is amplified by the amplifier 36U, and then its positive and negative sides are inverted by the complementary MOS 36U. Depending on the positive and negative states of the gate signal input from the control device 10, the complementary MOS 38U may be omitted.

[0027] The operation unit 34U is a variable resistor that changes its resistance value under the control of the SW speed control unit 32U to change the current value of the gate waveform applied to the gate of the switching element 44U. The operation unit 34U includes a variable resistor 34UO that changes a gate charge current, which is a current of a gate waveform of a positive voltage applied to the gate of the switching element 44U, and a variable resistor 34UF that changes a gate discharge current, which is a current of a gate waveform of a negative voltage applied to the gate of the switching element 44U. For example, the switching transition time of the switching elements 42U to 44W from OFF to ON can be shortened by increasing the gate charge current during the switching. Also, the switching transition time of the switching elements 42U to 44W from ON to OFF can be shortened by increasing the gate discharge current during the switching.

[0028] 3 is a block diagram showing an example of a specific configuration of the control device 10. The control device 10 is a type of computer, and includes a CPU (Central Processing Unit) 14, a ROM (Read Only Memory) 16, a RAM (Random Access Memory) 18, and an input / output port 20.

[0029] In the control device 10, the CPU 14, ROM 16, RAM 18, and an input / output port 20 are connected to one another via various buses such as an address bus, a data bus, and a control bus. The input / output port 20 is connected to various input / output devices such as a voltage detection unit 26, a current detection unit 28, and a gate drive circuit 30.

[0030] The ROM 16 is installed with a modulation command generating program for generating a switching pattern and a gate signal for the switching elements 42U-44W, and a SW speed command program for generating a SW speed command value. In this embodiment, the CPU 14 executes the modulation command generating program to generate a switching pattern and a gate signal for the switching elements 42U-44W. The CPU 14 also generates a SW speed command value according to the SW speed command program. The RAM 18 is a storage unit that temporarily stores data, and holds, for example, data input from the rotation angle sensor 24, the voltage detection unit 26, and the current detection unit 28, etc.

[0031] Next, a description will be given of various functions realized by the CPU 14 of the control device 10 executing the modulation command generation program and the SW speed command program. By the CPU 14 executing the modulation command generation program and the SW speed command program, the CPU 14 functions as a switching pattern selection unit 14A that generates switching patterns and gate signals for the switching elements 42U to 44W and a SW speed command generation unit 14B that generates a SW speed command value, as shown in FIG.

[0032] 4 is a flowchart showing an example of a gate signal / SW speed command value output process of the control device 10 for a rotating electric machine according to this embodiment. In step 100, sensor information such as the rotation angle of the rotor of the motor 12 detected by the rotation angle sensor 24, the power supply voltage detected by the voltage detection unit 26, and the phase current detected by the current detection unit 28 is acquired.

[0033] In step 102 , a voltage command vector is generated based on the sensor information acquired in step 100 .

[0034] The power supply voltage detected by the voltage detection unit 26 is used to adjust the effective voltage of the current supplied to the windings of the motor 12. In space vector modulation, the effective voltage is adjusted by a modulation factor that is a value between 0 and 1 proportional to the magnitude of the voltage command vector, and the effective voltage increases as the modulation factor increases, and decreases as the modulation factor decreases. In this embodiment, when the power supply voltage detected by the voltage detection unit 26 is high, the modulation factor of the voltage command vector is reduced to suppress the effective voltage, and when the power supply voltage detected by the voltage detection unit 26 is low, the modulation factor of the voltage command vector is increased to increase the effective voltage.

[0035] The phase currents detected by current detection unit 28 indicate the current values ​​of each of the three phases U, V, and W. In step 102, each current value is converted into digital values ​​Iu, Iv, and Iw. Based on the fact that an ideal three-phase AC becomes 0 when three sine waves are added (Iu+Iv+Iw=0), the Clarke transformation that converts three phases to two phases is used to calculate the following two-phase current values ​​Iα and Iβ from Iu, Iv, and Iw.

[0036] JPEG0007619225000001.jpg1967

[0037] The two-phase current values ​​Iα and Iβ calculated by the Clarke transformation are values ​​in a fixed coordinate system, so they are converted by the Park transformation into current values ​​Id and Iq in a rotating coordinate system based on the rotating rotor of the motor 12. If the current values ​​in the fixed coordinate system are Iα and Iβ, and the rotation angle of the rotor detected by the rotation angle sensor 24 is θ, then the two-phase current values ​​Id and Iq in the rotating coordinate system are as follows by the Park transformation:

[0038] JPEG0007619225000002.jpg1982

[0039] The two-phase current values ​​Id, Iq in the rotating coordinate system are controlled by PI control which performs in parallel P control (proportional control), which amplifies and controls the difference between a predetermined ideal value and the actual measured current values ​​Id, Iq, and I control (integral control), which amplifies and controls the difference according to the integral value of this difference, so that the current is reduced when the actual measured current values ​​Id, Iq are larger than the ideal value, and the current is increased when they are smaller than the ideal value.

[0040] As a result of the PI control, the two-phase current values ​​Id, Iq in the rotating coordinate system become two-phase voltage values ​​Vg, Vd in the rotating coordinate system. If the rotation angle of the rotor detected by the rotation angle sensor 24 is θ, the two-phase voltage values ​​Vg, Vd in the rotating coordinate system are transformed into two-phase voltage values ​​Vα, Vβ in the fixed coordinate system by inverse Park transformation as shown below.

[0041] JPEG0007619225000003.jpg1881

[0042] The voltage values ​​Vα and Vβ are vector quantities, and a composite vector of Vα and Vβ becomes a voltage command vector Ve as shown in Fig. 8. The generated voltage command vector Ve has a modulation factor adjusted based on the power supply voltage detected by the voltage detection unit 26. The generated voltage command vector Ve is treated as a composite vector of voltage vectors V0-V7 corresponding to the switching patterns of the switching elements 42U-44W as shown in Fig. 7. The control device 10 generates gate signals indicating the switching patterns of the voltage vectors V0-V7, etc., and outputs them to the gate drive circuit 30.

[0043] In step 104, the switching pattern of the switching elements 42U to 44W indicated by the generated voltage command vector Ve is referenced, and it is determined whether or not there are switching overlap timings 110A and 110B as shown in FIG.

[0044] At switching overlap timing 110A in FIG. 5, U-phase switching element 42U switches from off to on and U-phase switching element 44U switches from on to off, while V-phase switching element 42V switches from on to off and V-phase switching element 44V switches from off to on.

[0045] Also, at switching overlap timing 110B in FIG. 5, the V-phase switching element 42V switches from off to on, and the V-phase switching element 44V switches from on to off, while the W-phase switching element 42W switches from on to off, and the W-phase switching element 44W switches from off to on.

[0046] In step 104, if the switching timings of the switching elements in the two phases overlap, such as switching overlap timings 110A and 110B, the procedure proceeds to step 106, and if the switching timings of the switching elements in the two phases do not overlap, the procedure proceeds to step 108.

[0047] In step 106, when the switching timings of the switching elements overlap in two phases, as in switching overlap timings 110A and 110B in Fig. 5, a SW speed command value is generated to shorten the switching transition time of the switching elements at that timing to a shorter time than the normal time. Reducing the switching transition time of the switching elements can reduce the switching loss of the switching elements, but the generation of noise becomes noticeable. However, when the switching timings of the switching elements overlap in two phases, the fluctuation of the neutral point voltage of the motor 12 due to the switching of the switching elements, which causes noise, is suppressed.

[0048] 5, the neutral point voltage is suppressed from fluctuating at switching overlap timings 110A and 110B, but fluctuates such that the center point voltage rises at switching timing 112A when W-phase switching elements 42W and 44W are switched, and the center point voltage falls at switching timing 112B when U-phase switching elements 42U and 44U are switched. Since the switching timings of the switching elements do not overlap in two phases at switching timings 112A and 112B, the gate drive circuit 30 is controlled so that the switching transition time of the switching elements is normal.

[0049] Fig. 6 is an explanatory diagram showing the mechanism of noise generation. As shown in Fig. 6, noise that becomes a problem in controlling a rotating electric machine includes normal mode noise 90 and common mode noise 92. The normal mode noise 90 is noise that passes through a line between an inverter 40 having switching elements 42U-44W, which are noise sources, and a DC power supply 80. The normal mode noise 90 is generated due to high frequency components of an inverter current 130 shown in Fig. 12, which will be described later.

[0050] Common mode noise 92 is generated when high frequency components of a neutral point voltage 94 of the motor 12 flow through the housing or the ground area via stray capacitances 84, 86, etc., and is particularly problematic in the configuration shown in Fig. 1. In this embodiment, the switching timing of the switching elements in two phases is overlapped to suppress fluctuations in the neutral point voltage 94, thereby suppressing the generation of common mode noise.

[0051] In step 108, a gate signal based on the voltage command vector Ve and a SW speed command value are output to the gate drive circuit 30, and the process returns.

[0052] Fig. 7 is a table showing switching modes corresponding to voltage vectors V0 to V7 of the switching elements 42U to 44W constituting the inverter 40, and a neutral point voltage 94 of the motor 12. In Fig. 7, the voltage vectors V0 and V7 are both reactive voltage vectors, and show switching patterns when no current is applied to the coils of the motor 12. Specifically, the voltage vector V0 shows a switching pattern in which the switching elements 42U, 42V, and 42W are each turned off, and the switching elements 44U, 44V, and 44W are each turned on, and the neutral voltage is 0. Moreover, the voltage vector V7 shows a switching pattern in which the switching elements 42U, 42V, and 42W are each turned on, and the switching elements 44U, 44V, and 44W are each turned off, and the neutral point voltage 94 is equal to the power supply voltage VB.

[0053] The voltage vectors V1 to V6 each indicate a switching pattern for energizing the coils of the motor 12, and are therefore called effective voltage vectors.

[0054] Voltage vector V1 indicates a switching pattern in which switching element 42U is on, switching element 44U is off, switching elements 42V and 42W are both off, and switching elements 44V and 44W are both on, and neutral point voltage 94 becomes 1 / 3 of power supply voltage VB.

[0055] Voltage vector V2 indicates a switching pattern in which switching elements 42U and 42V are on, switching elements 44U and 44V are off, switching element 42W is off, and switching element 44W is on, and neutral point voltage 94 becomes ⅔ of power supply voltage VB.

[0056] Voltage vector V3 indicates a switching pattern in which switching element 42V is on, switching element 44V is off, switching elements 42U and 42W are each off, and switching elements 44U and 44W are each on, and neutral point voltage 94 becomes 1 / 3 of power supply voltage VB.

[0057] Voltage vector V4 indicates a switching pattern in which switching elements 42V and 42W are on, switching elements 44V and 44W are off, switching element 42U is off, and switching element 44U is on, and neutral point voltage 94 becomes ⅔ of power supply voltage VB.

[0058] Voltage vector V5 indicates a switching pattern in which switching element 42W is on, switching element 44W is off, switching elements 42U and 42V are each off, and switching elements 44U and 44V are each on, and neutral point voltage 94 becomes 1 / 3 of power supply voltage VB.

[0059] Voltage vector V6 indicates a switching pattern in which switching elements 42U and 42W are on, switching elements 44U and 44W are off, switching element 42V is off, and switching element 44V is on, and neutral point voltage 94 becomes ⅔ of power supply voltage VB.

[0060] 8 is a schematic diagram showing an example of a voltage command vector Ve. The voltage command vector Ve can be regarded as a combination of a voltage vector V1 and a voltage vector V2, or as a combination of a voltage vector V1 and a voltage vector V3. It can also be regarded as a combination of a voltage vector V6 and a voltage vector V2.

[0061] In this embodiment, when setting the switching patterns of the switching elements 42U to 44W based on the voltage command vector Ve, voltage vectors V1 to V6 are selected such that the switching timings of the switching elements in two phases overlap.

[0062] FIG. 9(A) is an explanatory diagram showing an example of a transition of a voltage vector in the switching pattern of the switching elements 42U to 44W shown in FIG. 5, and FIG. 9(B) is an explanatory diagram showing the switching pattern of the transitioning voltage vector.

[0063] 9(A) and 9(B) as (1) and (2), when the voltage vector is switched from V3 to V1, the switching pattern is changed from one in which the switching element 42V is on, the switching element 44V is off, the switching elements 42U and 42W are each off, and the switching elements 44U and 44W are each on to one in which the switching element 42U is on, the switching element 44U is off, the switching elements 42V and 42W are each off, and the switching elements 44V and 44W are each on. As a result, overlapping of switching occurs in two phases such that the switching element 42U is switched from off to on and the switching element 42V is switched from on to off, and as a result, fluctuations in the neutral point voltage 94 of the motor 12 are suppressed, and the generation of common mode noise is suppressed.

[0064] 9(A) and 9(B) as (3) and (4), when the voltage vector is switched from V6 to V2, the switching pattern in which the switching elements 42U and 42W are on, the switching elements 44U and 44W are off, the switching element 42V is off, and the switching element 44V is on is switched to the switching pattern in which the switching elements 42U and 42V are on, the switching elements 44U and 44V are off, the switching element 42W is off, and the switching element 44W is on. As a result, overlapping of switching occurs in two phases such that the switching element 42V is switched from off to on and the switching element 42W is switched from on to off, and as a result, fluctuations in the neutral point voltage 94 of the motor 12 are suppressed, and the generation of common mode noise is suppressed.

[0065] As shown in Figures 9(A) and 9(B), when the switching of two phases overlap, the generation of common mode noise is suppressed, so by increasing the current value of the gate signal applied to the gates of the switching elements 42U-44W, the switching transition time of the switching elements 42U-44W can be shortened, and as a result, the switching loss of the switching elements 42U-44W can be reduced.

[0066] Fig. 10 is an explanatory diagram of a case where switching of switching elements 42U to 44W is controlled by voltage vectors with a phase difference of 120 degrees. In the case shown in Fig. 9(A) as well, at the timing when switching of two phases overlaps, the voltage vectors switch with a phase difference of 120 degrees. For example, the phase difference between voltage vector V3 and voltage vector V1, and the phase difference between voltage vector V6 and voltage vector V2 are each 120 degrees. In the case shown in Fig. 10, the switching of switching elements 42U to 44W is controlled by a switching pattern in which the voltage vectors switch with a phase difference of 120 degrees.

[0067] Fig. 11 is an explanatory diagram showing an example of the switching patterns of each phase and fluctuations in the neutral point voltage 94 when the voltage vector switches with a phase difference of 120 degrees. In Fig. 11, the voltage vector switches from V4 to V2, V2 to V6, V6 to V2, and V2 to V4, respectively.

[0068] When the voltage vector switches from V4 to V2, switching overlap timing 114A occurs where switching in two phases overlaps such that switching element 42U switches from off to on and switching element 42W switches from on to off.

[0069] When the voltage vector switches from V2 to V6, switching overlap timing 114B occurs where switching in two phases overlaps such that switching element 42W switches from off to on and switching element 42V switches from on to off.

[0070] When the voltage vector switches from V6 to V2, there occurs a switching overlap timing 114C where switching in two phases overlaps such that switching element 42V switches from off to on and switching element 42W switches from on to off.

[0071] When the voltage vector switches from V2 to V4, switching overlap timing 114D occurs where switching in two phases overlaps such that switching element 42W switches from off to on and switching element 42U switches from on to off.

[0072] 11, the voltage vectors are switched with a phase difference of 120 degrees, and as a result, the switching is overlapped in two phases, so that the neutral point voltage 94 of the motor 12 becomes approximately constant. As a result, the occurrence of common mode noise caused by fluctuations in the neutral point voltage 94 is suppressed.

[0073] As described above, according to this embodiment, at the timing when the switching of the switching elements overlaps in two phases, fluctuations in the neutral point voltage 94 of the motor 12, which causes the common mode noise 92, are suppressed. Therefore, in this embodiment, at the timing when the switching of the switching elements overlaps in two phases, such as switching overlap timing 110A in Fig. 5, by controlling the gate drive circuit 30 so that the switching transition time of the switching elements of each phase becomes a shortened time that is shorter than a normal time, it is possible to reduce the switching loss of the switching elements 42U to 44W while suppressing the common mode noise 92.

[0074] [Second embodiment] Next, a second embodiment of the present invention will be described. Fig. 12 is a schematic diagram showing an example of the configuration of a rotating electric machine equipped with two inverter systems. The configuration of the two inverter systems, inverter 40A and inverter 40B, is substantially the same as that of the inverter 40 of the first embodiment shown in Fig. 1, so a detailed description will be omitted. In addition, a DC power supply 80 and a smoothing capacitor 82 are also the same as those of the first embodiment, so the same reference numerals as those of the first embodiment are used for such configurations, and a detailed description will be omitted.

[0075] As an example, motor 120, which is a rotating electric machine, has two systems of coils, one to which power is supplied from inverter 40A and the other to which power is supplied from inverter 40B. Operation of inverter 40A generates inverter (INV) current (A system) 130A, and operation of inverter 40B generates inverter (INV) current (B system) 130B, and inverter (INV) current (A+B) 130 is generated in a circuit including DC power supply 80 and inverters 40A, 40B.

[0076] Fluctuations in the input / output currents of the inverters 40A, 40B, such as the inverter currents 130, 130A, 130B, can be a cause of the normal mode noise 90 described with reference to Fig. 6. However, when the waveform of one system of the inverters 40A, 40B rises and the waveform of the other system falls, the inverter currents 130A, 130B are offset with each other, and as a result, the fluctuation of the inverter current 130 is suppressed. In this embodiment, the switching transition time of the switching elements 42U-44W is shortened to a shorter time than the normal time at the timing when the fluctuation of the inverter current 130 is suppressed, thereby reducing the switching loss of the switching elements 42U-44W while suppressing the generation of normal mode noise.

[0077] FIG. 13 is an explanatory diagram showing an example of changes in the voltage vectors and inverter currents 130A and 130B of the inverters 40A and 40B, and changes in the inverter current 130. In FIG.

[0078] As described above, among the voltage vectors V0 to V7, the voltage vectors V0 and V7 are reactive voltage vectors that indicate the switching pattern when no current is applied to the coils of the motor 12. Therefore, when the voltage vectors are reactive voltage vectors V0 and V7, the waveforms of the inverter currents 130A and 130B each fall, as indicated by "reactive" in FIG.

[0079] In FIG. 13, when the voltage vector of the A system switches from the reactive voltage vector V7 to the active voltage vector V2, the so-called upper arm switch (corresponding to switching element 42W in FIG. 1) of the W phase in the inverter 40A switches from on to off, and the so-called lower arm switch (corresponding to switching element 44W in FIG. 1) switches from off to on, causing the inverter current 130A of the A system to rise by a current value of -Iw from a falling state.

[0080] When the voltage vector in system A switches from the reactive voltage vector V7 to the active voltage vector V2 and at the same time the voltage vector in system B switches from the active voltage vector V2 to the reactive voltage vector V7, the upper arm switch (corresponding to switching element 42W in Figure 1) of the W phase in inverter 40B switches from off to on, and the lower arm switch (corresponding to switching element 44W in Figure 1) switches from on to off, causing inverter current 130B of system B to change from a rising state of -Iw in current value to a falling state.

[0081] As a result, the current value of inverter current 130, which is the sum of the A and B systems, remains at -Iw even when each of inverters 40A, 40B is switched.

[0082] 13, after switching overlap timing 116A, the voltage vector in system A switches from active voltage vector V2 to active voltage vector V1, but the voltage vector in system B remains as reactive voltage vector V7. However, when the voltage vector in system A switches from active voltage vector V1 to reactive voltage vector V0 at switching overlap timing 116B, the upper arm switch (corresponding to switching element 42U in FIG. 1) of the U phase in inverter 40A switches from on to off, and the lower arm switch (corresponding to switching element 44U in FIG. 1) switches from off to on, so that inverter current 130A in system A switches from a rising state to a falling state in current value Iu.

[0083] When the voltage vector in system A switches from the active voltage vector V1 to the reactive voltage vector V0 and at the same time the voltage vector in system B switches from the reactive voltage vector V7 to the active voltage vector V2, the upper arm switch of the W phase in inverter 40B switches from on to off and the lower arm switch switches from off to on, respectively, causing the inverter current 130B of system B to rise from a falling state to a current value of -Iw.

[0084] As a result, the current value of inverter current 130, which is the sum of the A and B systems, becomes −Iw when each of inverters 40A, 40B is switched.

[0085] 13, after switching overlap timing 116B, the voltage vector in system A remains as reactive voltage vector V0, but the voltage vector in system B switches from active voltage vector V2 to active voltage vector V1. However, at switching overlap timing 116C, when the voltage vector in system A switches from reactive voltage vector V0 to active voltage vector V1, the upper arm switch of the U phase in inverter 40A switches from off to on and the lower arm switch switches from on to off, respectively, so that inverter current 130A in system A switches from a falling state to a rising state by a current value Iu.

[0086] When the voltage vector in system A switches from the reactive voltage vector V0 to the active voltage vector V1 and at the same time the voltage vector in system B switches from the active voltage vector V1 to the reactive voltage vector V0, the upper arm switch (corresponding to switching element 42U in Figure 1) of the U phase in inverter 40B switches from on to off, and the lower arm switch (corresponding to switching element 44U in Figure 1) switches from off to on, respectively, causing inverter current 130B of system B to change from a rising state of Iu to a falling state in current value.

[0087] As a result, the current value of inverter current 130, which is the sum of the A and B systems, maintains the state of Iu even when each of inverters 40A, 40B is switched.

[0088] 13, after switching overlap timing 116C, the voltage vector in system A switches from the active voltage vector V1 to the active voltage vector V2, but the voltage vector in system B remains as the reactive voltage vector V0. However, at switching overlap timing 116D, when the voltage vector in system A switches from the active voltage vector V2 to the reactive voltage vector V7, the upper arm switch of the W phase in inverter 40A switches from off to on and the lower arm switch switches from on to off, respectively, so that the inverter current 130A in system A switches from a rising state of -Iw to a falling state in current value.

[0089] When the voltage vector in system A switches from the active voltage vector V2 to the reactive voltage vector V7, and at the same time the voltage vector in system B switches from the reactive voltage vector V0 to the active voltage vector V1, the upper arm switch of the U phase in inverter 40B switches from off to on, and the lower arm switch switches from on to off, respectively, causing inverter current 130B of system B to rise from a falling state by a current value Iu.

[0090] As a result, the current value of inverter current 130, which is the sum of the A and B systems, becomes Iu when each of inverters 40A, 40B is switched.

[0091] 13, even during switching at the switching overlap timings 116A, 116B, 116C, and 116D, the current value of the inverter current 130 of the A system and the B system combined is −Iw or Iu, and fluctuations are suppressed. As a result, the generation of common mode noise 92 can also be suppressed.

[0092] In this embodiment, at switching overlap timings 116A, 116B, 116C, and 116D when the voltage vector in one system switches from a reactive voltage vector to an active voltage vector and the voltage vector in the other system switches from an active voltage vector to a reactive voltage vector, the switching transition time of the switching elements in each of the inverters 40A and 40B is shortened to a time shorter than a normal time, thereby reducing the switching loss of the switching elements.

[0093] [Third embodiment] Next, a third embodiment of the present invention will be described. Fig. 14(A) is an explanatory diagram of a case where, at the switching overlap timing 110A etc. in Fig. 5 etc. of the first embodiment, the absolute value of the rate of change of the switching transition time of the switching element of the A phase (U phase at the switching overlap timing 110A in Fig. 5) is different from the absolute value of the rate of change of the switching transition time of the switching element of the B phase (V phase at the switching overlap timing 110A in Fig. 5) different from the A phase. Fig. 14(B) is an explanatory diagram of a case where, at the switching overlap timing 110A etc. in Fig. 5 etc. of the first embodiment, the absolute value of the rate of change of the switching transition time of the switching element of the A phase (U phase at the switching overlap timing 110A in Fig. 5) is the same as the absolute value of the rate of change of the switching transition time of the switching element of the B phase (V phase at the switching overlap timing 110A in Fig. 5) different from the A phase. It should be noted that the A-phase switching waveforms 140A, 150A and the B-phase switching waveforms 140B, 150B in FIGS. 14(A) and 14(B) are the drain-source voltages of the switching elements 42U to 44W, respectively.

[0094] 14A, the absolute value of A-phase gradient 142A, which is the gradient of A-phase switching waveform 140A indicating the rate of change of the switching transition time of the A-phase switching element, is greater than the absolute value of B-phase gradient 142B, which is the gradient of B-phase switching waveform 140B indicating the rate of change of the switching transition time of the B-phase switching element. As a result, fluctuations occur in composite voltage waveform 144 of A-phase switching waveform 140A and B-phase switching waveform 140B, and the high-frequency components that cause common-mode noise 92 are diffused to the surroundings along with the fluctuation of composite voltage waveform 144.

[0095] 14B, the absolute value of A-phase gradient 152A, which is the gradient of A-phase switching waveform 150A indicating the rate of change of the switching transition time of the A-phase switching element, is approximately the same as the absolute value of B-phase gradient 152B, which is the gradient of B-phase switching waveform 150B indicating the rate of change of the switching transition time of the B-phase switching element. As a result, the respective changes of A-phase switching waveform 150A and B-phase switching waveform 150B are offset, no fluctuation occurs in composite voltage waveform 154 of A-phase switching waveform 150A and B-phase switching waveform 150B, and the generation of high-frequency components that cause common mode noise 92 is suppressed.

[0096] As described above, according to this embodiment, at the timing when the switching of the switching elements overlaps in two phases, the absolute values ​​of the change rates of the switching transition times of the switching elements of the two phases are made substantially identical, thereby making it possible to suppress the common mode noise 92. Therefore, in this embodiment, at the timing when the switching of the switching elements overlaps in two phases, such as switching overlap timing 110A in Fig. 5, by shortening the switching transition time of the switching elements of each phase from a normal time so that the absolute values ​​of the change rates of the switching transition times of the switching elements of each phase are made substantially identical, it becomes possible to reduce the switching loss of the switching elements 42U to 44W while suppressing the common mode noise 92. [Explanation of symbols]

[0097] 10...control device, 12...motor, 14...CPU, 14A...switching pattern selection unit, 14B...speed command generation unit, 30 (30UA, 30UB, 30VA, 30VB, 30WA, 30WB)...gate drive circuit, 40, 40A, 40B...inverter, 42U, 42V, 42W, 44U, 44V, 44W...switching element, 80...DC power supply, 90...normal mode noise, 92...common mode noise, 94...neutral Point voltage, 110A, 110B...switching overlap timing, 112A, 112B...switching timing, 114A, 114B, 114C, 114D, 116A, 116B, 116C, 116D...switching overlap timing, 120...motor, 130, 130A, 130B...inverter current, 140A...A-phase switching waveform, 140B...B-phase switching waveform, 142A...A-phase gradient, 142B...B-phase gradient 144...Composite voltage waveform, 150A...A-phase switching waveform, 150B...B-phase switching waveform, 152A...A-phase gradient, 152B...B-phase gradient, 154...Composite voltage waveform, V0, V7...Reactive voltage vector, V1, V2, V3, V4, V5, V6...Active voltage vector, Ve...Voltage command vector

Claims

1. a power conversion circuit (40) that outputs three-phase AC generated from power supplied from a DC power source (80) by switching a plurality of switching elements (42U to 44W) to a winding of a rotating electric machine (12); a gate drive circuit (30) that adjusts a current flowing through the gates of the plurality of switching elements (42U to 44W) to change a switching transition time of the plurality of switching elements (42U to 44W) to either a normal time or a shortened time that is shorter than the normal time; a switching control unit (10) that controls a switching timing of the plurality of switching elements (42U to 44W) and controls the gate drive circuit (30) so that a transition time of each of the switching elements (42U to 44W) of any one of the phases and the switching elements (42U to 44W) of the other phases becomes the shortened time at a timing when a change in physical quantity caused by the switching of the switching elements (42U to 44W) of any one of the phases and a change in physical quantity caused by the switching of the switching elements (42U to 44W) of the other phases different from the any one of the phases are offset; A control device for a rotating electric machine including the same.

2. 2. The control device for a rotating electric machine according to claim 1, wherein the physical quantity is a neutral point voltage (94) of the rotating electric machine (12), and the switching control unit (10) controls the gate drive circuit (30) so that, at a timing when a switching element (42U, 42V, 42W) which is an upper arm switch of any of the phases is switched from on to off and a switching element (42U, 42V, 42W) which is an upper arm switch of another phase different from any of the phases is switched from off to on, the switching transition time of each of the switching elements (42U to 44W) of the any of the phases and the switching elements (42U to 44W) of the other phases becomes the shortened time.

3. 3. The control device for a rotating electric machine according to claim 2, wherein the power conversion circuit (40) is a three-phase inverter of one system, and the switching control unit (10) controls the gate drive circuit (30) so that the switching transition time of the switching elements (42U to 44W) that switch at a timing when a phase difference before and after switching of a voltage vector indicating the switching timing of the multiple switching elements (42U to 44W) becomes 120 degrees is the shortened time.

4. 2. The control device for a rotating electric machine according to claim 1, wherein the power conversion circuits (40A, 40B) are two systems of three-phase inverters, the physical quantity is an input / output current of the three-phase inverters, and the switching control unit (10) controls the gate drive circuit (30) so that a switching transition time of each of the switching elements that switches at a timing when a voltage vector indicating a switching timing of the switching elements in one system of the three-phase inverter switches from an effective voltage vector to a reactive voltage vector, and when the voltage vector switches from a reactive voltage vector to an effective voltage vector in the other system of the three-phase inverter, becomes the shortened time.

5. The control device for a rotating electric machine according to claim 2, wherein the switching control unit (10) controls the gate drive circuit (30) so that an absolute value of a rate of change of a switching transition time when a switching element (42U to 44W) of any of the phases is switched from on to off is approximately equal to an absolute value of a rate of change of a switching transition time when a switching element (42U to 44W) of another phase different from any of the phases is switched from off to on.

6. A method for controlling a rotating electric machine to which three-phase AC generated from power supplied from a DC power source (80) is supplied by switching a plurality of switching elements (42U to 44W) constituting a power conversion circuit (40), comprising: A method for controlling a rotating electric machine, comprising: controlling a switching timing of the plurality of switching elements (42U to 44W); and controlling a current passed through a gate of each of the switching elements (42U to 44W) of any one of the phases and the switching elements (42U to 44W) of the other phases so that a switching transition time of each of the switching elements (42U to 44W) of any one of the phases and the switching elements (42U to 44W) of the other phases becomes a shortened time that is shorter than a normal time, at a timing at which a fluctuation in a physical quantity caused by the switching of the switching element (42U to 44W) of any one of the phases and a fluctuation in a physical quantity caused by the switching of the switching element (42U to 44W) of another phase different from the any one of the phases are offset.

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