WO2020171110A1

WO2020171110A1 - Inverter device

Info

Publication number: WO2020171110A1
Application number: PCT/JP2020/006457
Authority: WO
Inventors: 辰樹柏原
Original assignee: サンデンホールディングス株式会社
Priority date: 2019-02-22
Filing date: 2020-02-19
Publication date: 2020-08-27
Also published as: CN113454899A; JP2020137329A; JP7221726B2

Abstract

Provided is an inverter device that makes it possible to effectively eliminate or reduce common mode noise. An inverter device 1 comprises an inverter circuit 28 and a control device 21. The inverter circuit connects upper arm switching elements 18A–18C and lower arm switching elements 18D–18F of respective phases in series between an upper arm power supply line 10 and a lower arm power supply line 15, and applies the voltages at the contact points between the upper and lower arm switching elements of the phases to a motor 8 as three-phase alternating-current output. The control device synchronizes the switching timing of the upper and lower arm switching elements of the phases and, by means of changes in the other phase voltages, cancels changes in the phase voltage applied to the motor.

Description

Inverter device

The present invention relates to an inverter device in which an AC voltage is applied to a motor by an inverter circuit to drive the motor.

Conventionally, an inverter device for driving a motor has a three-phase inverter circuit composed of a plurality of switching elements, PWM (Pulse Width Modulation) control of the switching elements of each UVW phase, and a voltage waveform close to a sine wave to the motor. However, the common mode noise generated by the fluctuation of the neutral point potential of the motor has been a problem.

In the case of a motor that constitutes an electric compressor, for example, this common mode noise is generated by the common mode current leaking through the stray capacitance between the casing of the compressor and the ground. I was satisfied.

Japanese Patent No. 4276097 Japanese Patent No. 5093452

However, the installation of such a noise filter causes the device to become large in size, and the cost also rises. On the other hand, since the neutral point potential of the motor is obtained from the average of each phase voltage, a method of adjusting the variation of the phase voltage due to the switching of the switching element to suppress the variation of the neutral point potential of the motor is also proposed. (For example, see Patent Document 1 and Patent Document 2).

The present invention has been made in consideration of such a conventional situation, and an object thereof is to provide an inverter device that can effectively eliminate or suppress common mode noise.

In the inverter device of the present invention, an upper arm switching element and a lower arm switching element are connected in series for each phase between the upper arm power supply line and the lower arm power supply line, and the voltage at the connection point of the upper and lower arm switching elements of each phase is connected. Is provided as a three-phase AC output to the motor, and a controller for controlling the switching of the upper and lower arm switching elements of each phase of this inverter circuit. It is characterized in that the switching timings of the elements are synchronized and changes in the phase voltage applied to the motor are canceled by changes in other phase voltages.

In the inverter device according to a second aspect of the present invention, in the control device according to the above aspect, the switching timings of the upper and lower arm switching elements of each phase are synchronized, and the change of the phase voltage is canceled by the change of the other phase voltage. It is characterized by generating a voltage command value and controlling the inverter circuit.

In the inverter device of the invention of claim 3, in each of the above inventions, the control device is such that the switching timings of the upper and lower arm switching elements are synchronized according to the direction of the current flowing through the motor, and the change in the phase voltage is different from that of the other phase voltage. It is characterized in that the voltage command value is changed so as to be canceled by the change.

In the inverter device of the invention according to claim 4, in each of the above inventions, the control device specifies switching from a state in which the lower arm switching element of one phase is turned on and the upper arm switching elements of the other two phases are turned on. It is characterized by starting a section.

In the inverter device according to a fifth aspect of the present invention, in the control device according to the first aspect of the present invention, the lower arm switching element of any two phases is turned on and the upper arm switching element of another one phase is turned on. It is characterized in that the specified section of switching is started from the state in which it is in the open state.

According to the present invention, between the upper arm power supply line and the lower arm power supply line, the upper arm switching element and the lower arm switching element are connected in series for each phase, and the voltage at the connection point of the upper and lower arm switching elements for each phase is In an inverter device equipped with an inverter circuit that applies a three-phase AC output to a motor and a control device that controls the switching of the upper and lower arm switching elements of each phase of the inverter circuit, the control device controls the upper and lower arm switching elements of each phase. Since the switching timing is synchronized and the change in the phase voltage applied to the motor is canceled by the change in the other phase voltage, the fluctuation of the neutral point potential of the motor is eliminated by the switching timing of the switching element, or , Can be significantly suppressed. This makes it possible to effectively eliminate or suppress the occurrence of common mode noise.

In this case, in practice, the control device according to the second aspect of the present invention controls the phase of each phase in which the switching timings of the upper and lower arm switching elements of each phase are synchronized and the change of the phase voltage is canceled by the change of the other phase voltage. The voltage command value is generated to control the inverter circuit.

▽ Here, the phase voltage at the dead time considered when switching the switching element changes according to the direction of the current flowing through the motor. Therefore, in the control device according to the invention of claim 3, the switching timings of the upper and lower arm switching elements are synchronized according to the direction of the current flowing through the motor, and the change of the phase voltage is canceled by the change of the other phase voltage. By changing the voltage command value to 1, it is possible to eliminate or suppress the fluctuation of the neutral point potential regardless of the direction of the current flowing through the motor.

Further, the control device according to the invention of claim 4 starts the specified section of switching from a state in which the lower arm switching element of any one phase is turned on and the upper arm switching elements of the other two phases are turned on, Alternatively, the control device according to the invention of claim 5 starts the specified section of switching from a state in which the lower arm switching element of any two phases is turned on and the upper arm switching element of the other one phase is turned on. In this case, the change in the phase voltage can be smoothly canceled by the change in the other phase voltage.

It is an electric circuit diagram of the inverter device of one example of the present invention. It is the figure which showed collectively the voltage vectors V1-V6 which drive the motor of FIG. It is a figure explaining the production|generation of the voltage vector V0 by the control apparatus of the inverter apparatus of FIG. It is a figure explaining the production|generation of the voltage vector V1 by the control apparatus of the inverter apparatus of FIG. It is a figure explaining the production|generation of another voltage vector V1 by the control apparatus of the inverter apparatus of FIG. It is a figure explaining generation|occurrence|production of the voltage vector V2 by the control apparatus of the inverter apparatus of FIG. It is a figure explaining the production|generation of the voltage vector V3 by the control apparatus of the inverter apparatus of FIG. It is a figure explaining generation|occurrence|production of the voltage vector V4 by the control apparatus of the inverter apparatus of FIG. It is a figure explaining generation|occurrence|production of the voltage vector V5 by the control apparatus of the inverter apparatus of FIG. It is a figure explaining the production|generation of the voltage vector V6 by the control apparatus of the inverter apparatus of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The inverter device 1 of the embodiment is mounted on a so-called inverter-integrated electric compressor in which a compression mechanism is driven by a motor 8, and the electric compressor constitutes, for example, a refrigerant circuit of a vehicle air conditioner.

(1) Configuration of Inverter Device 1 In FIG. 1, the inverter device 1 includes a three-phase inverter circuit (three-phase inverter circuit) 28 and a control device 21. The inverter circuit 28 is a circuit that converts a DC voltage of a DC power supply (battery of the vehicle: 300 V, for example) 29 into a three-phase AC voltage and applies it to the motor 8. The inverter circuit 28 has a U-phase half-bridge circuit 19U, a V-phase half-bridge circuit 19V, and a W-phase half-bridge circuit 19W, and the respective phase half-bridge circuits 19U-19W are respectively upper arm switching elements 18A-18C. And individual lower arm switching elements 18D to 18F. Further, a flywheel diode 31 is connected in antiparallel to each of the switching elements 18A to 18F.

Incidentally, each of the switching elements 18A to 18F is composed of an insulated gate bipolar transistor (IGBT) or the like in which a MOS structure is incorporated in the gate portion in the embodiment.

The upper end sides of the upper arm switching elements 18A to 18C of the inverter circuit 28 are connected to the DC power supply 29 and the upper arm power supply line (positive electrode side bus line) 10 of the smoothing capacitor 32. On the other hand, the lower end sides of the lower arm switching elements 18D to 18F of the inverter circuit 28 are connected to the DC power supply 29 and the lower arm power supply line (negative electrode side bus line) 15 of the smoothing capacitor 32.

In this case, the upper arm switching element 18A and the lower arm switching element 18D of the U-phase half bridge circuit 19U are connected in series, and the upper arm switching element 18B and the lower arm switching element 18E of the V phase half bridge circuit 19V are connected in series. An upper arm switching element 18C and a lower arm switching element 18F of the W-phase half bridge circuit 19W are connected in series.

The connection point between the upper arm switching element 18A and the lower arm switching element 18D of the U-phase half bridge circuit 19U is connected to the U-phase armature coil 2 of the motor 8, and the upper arm switching element of the V-phase half bridge circuit 19V. The connection point between 18B and the lower arm switching element 18E is connected to the V-phase armature coil 3 of the motor 8, and the connection point between the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half bridge circuit 19W is the motor. 8 is connected to the W-phase armature coil 4.

(2) Configuration of Control Device 21 The control device 21 is composed of a microcomputer having a processor, and in the embodiment, a rotation speed command value is input from the vehicle ECU and a phase current is input from the motor 8 and based on these. The ON/OFF state (switching) of each switching element 18A to 18F of the inverter circuit 28 is controlled. Specifically, the gate voltage applied to the gate terminals of the switching elements 18A to 18F is controlled.

The control device 21 of the embodiment includes the phase voltage command calculator 33, the PWM signal generator 36, the gate driver 37, and the U phase currents iu and V that are the motor currents (phase currents) of the respective phases flowing through the motor 8. It has

current sensors

26A and 26B formed of current transformers for measuring the current iv and the W-phase current iw, and the

current sensors

26A and 26B are connected to the phase voltage command calculator 33. The current sensor 26A measures the U-phase current iu, and the current sensor 26B measures the V-phase current iv. Then, the W-phase current iw is calculated from these. Besides measuring the motor current of each phase with the

current sensors

26A and 26B as in the embodiment, the current value of the lower arm power supply line 15 is detected and the phase voltage command is calculated from the current value and the operating state of the motor 8. The method of detecting/estimating each phase current, such as estimation by the unit 33, is not particularly limited.

The phase voltage command calculation unit 33 applies the U phase voltage Vu, V phase voltage Vv, W applied to the armature coils 2 to 4 of each phase of the motor 8 based on the electric angle of the motor 8, the current command value and the phase current. Three-phase modulation voltage command value Vu′ (hereinafter, U-phase voltage command value Vu′), Vv′ (hereinafter, V-phase voltage command value Vv′), Vw′ (hereinafter, W-phase voltage) for generating the phase voltage Vw The command value Vw') is calculated and generated.

The PWM signal generation unit 36 compares the three-phase modulation voltage command values Vu′, Vv′, Vw′ calculated by the phase voltage command calculation unit 33 with the triangular carrier (carrier triangular wave) to determine whether the inverter circuit The U-phase half-bridge circuit 19U, the V-phase half-bridge circuit 19V, and the W-phase half-bridge circuit 19W, which are 28 U-phase half-bridge circuits, generate a PWM signal as a drive command signal.

The gate driver 37, based on the PWM signal output from the PWM signal generation unit 36, outputs the gate voltage of the upper arm switching element 18A and the lower arm switching element 18D of the U-phase half bridge circuit 19U and the V-phase half bridge circuit 19V. The gate voltages of the arm switching element 18B and the lower arm switching element 18E and the gate voltages of the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half bridge circuit 19W are generated.

The switching elements 18A to 18F of the inverter circuit 28 are ON/OFF driven based on the gate voltage output from the gate driver 37. That is, when the gate voltage is in the ON state (predetermined voltage value), the switching element is ON, and when the gate voltage is in the OFF state (zero), the switching element is OFF. The gate driver 37 is a circuit for applying a gate voltage to the IGBT based on the PWM signal when the switching elements 18A to 18F are the above-described IGBTs, and is composed of a photocoupler, a logic IC, a transistor, and the like. It

Then, the voltage at the connection point between the upper arm switching element 18A and the lower arm switching element 18D of the U-phase half bridge circuit 19U is applied (output) to the U-phase armature coil 2 of the motor 8 as the U-phase voltage Vu (phase voltage). The voltage at the connection point between the upper arm switching element 18B and the lower arm switching element 18E of the V-phase half bridge circuit 19V is applied (output) to the V-phase armature coil 3 of the motor 8 as the V-phase voltage Vv (phase voltage). The voltage at the connection point between the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half bridge circuit 19W is applied (output) to the W-phase armature coil 4 of the motor 8 as the W-phase voltage Vw (phase voltage). To be done.

(3) Operation of Control Device 21 Next, the actual control operation of the control device 21 will be described with reference to FIGS. 2 to 10. The phase voltage command calculation unit 33 of the control device 21 of the inverter device 1 according to the present invention has a U-phase voltage command value Vu′, a V-phase voltage command value Vv′, and a V-phase voltage command value Vv′ that eliminate the fluctuation of the neutral point potential Vc of the motor 8. , W-phase voltage command value Vw′ (three-phase modulation voltage command value) is calculated, and voltage vectors V0 to V6 for driving the motor 8 are generated (collectively shown in FIG. 2). Then, one of the voltage vectors V0 to V6 is selected according to the above-described rotation speed command value, and the motor 8 is operated.

(3-1) Voltage vector V0
First, the generation of the voltage vector V0 of FIG. 2 will be described with reference to FIG. 3, the U-phase voltage command value Vu′, the V-phase voltage command value Vv′, the W-phase voltage command value Vw′, and the triangular carriers X1 to X4 generated by the phase voltage command calculation unit 33 of the control device 21 are shown in the uppermost stage. The second stage from the top shows the ON/OFF state of each switching element 18A to 18F, and the second stage from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the bottom stage. Indicates the neutral point potential Vc of the motor 8, respectively.

The directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing through the motor 8 are also shown on the right side. There are six combinations of the directions of the phase currents, and the direction flowing into the motor 8 is indicated by + and the direction flowing out from the motor 8 is indicated by −. The example of FIG. 3 is the case of the uppermost stage, and shows the case where the U-phase current iu and the V-phase current iv flow into the motor 8 and the W-phase current iw flows out of the motor 8.

Incidentally, in the embodiment, the triangular carrier is composed of two ascending X1 and X2 and two descending X3 and X4 in order to make a dead time. Uphill X2 is ahead of uphill X1, and downhill X4 is ahead of downhill X3. Then, in the first half of one carrier cycle, the PWM signal generation unit 36 compares the rising X1 of the triangular carrier with the respective voltage command values Vu′, Vv′, and Vw′ to determine whether the U-phase lower arm switching elements 18D and V-phase are A PWM signal for turning ON/OFF the upper arm switching element 18B and the W-phase upper arm switching element 18C is generated, and the rising X2 of the triangular carrier is compared with each voltage command value Vu′, Vv′, Vw′, A PWM signal for turning ON/OFF the U-phase upper arm switching element 18A, the V-phase lower arm switching element 18E, and the W-phase lower arm switching element 18F is generated.

In the latter half of one carrier cycle, the PWM signal generation unit 36 compares the downward X3 of the triangular carrier with the voltage command values Vu′, Vv′, Vw′, and the U-phase upper arm switching element 18A, the V-phase lower arm. A PWM signal for turning ON/OFF the switching element 18E and the lower arm switching element 18F of the W phase is generated, and the downward X4 of the triangular carrier is compared with each voltage command value Vu′, Vv′, Vw′, and the U phase is compared. A PWM signal for turning ON/OFF the lower arm switching element 18D, the V-phase upper arm switching element 18B, and the W-phase upper arm switching element 18C is generated.

Further, in the phase voltage command calculation unit 33, in the embodiment, the U-phase lower arm switching element 18D is ON, and the V-phase upper arm switching element 18B and the W-phase upper arm switching element 18C are ON. The specified section of switching starts from.

When the U-phase current iu and the V-phase current iv flow in the motor 8 and the W-phase current iw flows in the motor 8 as in the embodiment, the upper arm switching element 18A is turned on in the U phase. The U-phase voltage Vu becomes "H" during the period when the upper arm switching element 18B is ON even in the V phase, and the V-phase voltage Vv becomes "H" during the period when the upper arm switching element 18B is ON, and the lower arm switching element 18F is OFF during the W phase. The W-phase voltage Vw becomes “H” during the period. The sum of the widths of the "H" periods is the magnitude of the voltage of each phase, and the voltage vector V0 has the magnitude of "medium" for all three phases.

Further, as is apparent from this figure, the phase voltage command calculation unit 33 synchronizes the switching timing (ON/OFF timing) of the switching element that sets each phase voltage to “H” and changes the U phase voltage Vu. The voltage command values Vu′, Vv′, and Vw′ that are canceled by the changes in the V-phase voltage Vv and the W-phase voltage Vw are generated. As a result, the neutral point potential Vc, which is the average of the phase voltages Vu, Vv, and Vw, is always constant and does not change, so that common mode noise is eliminated.

(3-2) Voltage vector V1 (1)
Next, the generation of the voltage vector V1 of FIG. 2 will be described with reference to FIG. Also in FIG. 4, the uppermost stage shows the U-phase voltage command value Vu′, the V-phase voltage command value Vv′, the W-phase voltage command value Vw′ and the triangular carriers X1 to X4, and the second stage from the top shows each switching element 18A. 18F ON/OFF state, the second stage from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the bottom stage shows the neutral point potential Vc of the motor 8. There is.

Similarly, on the right side, the directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing in the motor 8 are shown. The example of FIG. 4 is also the case of the uppermost stage, and shows the case where the U-phase current iu and the V-phase current iv flow into the motor 8 and the W-phase current iw flows out of the motor 8.

The operation of the PWM signal generator 36 is the same as described above. Similarly, in the phase voltage command calculation unit 33, in the embodiment, the U-phase lower arm switching element 18D is turned on, and the V-phase upper arm switching element 18B and the W-phase upper arm switching element 18C are turned on. The specified section of switching is started from the state in which it is present.

When the U-phase current iu and the V-phase current iv flow in the motor 8 and the W-phase current iw flows in the motor 8 as in the embodiment, the upper arm switching element 18A is turned on in the U phase. The U-phase voltage Vu becomes "H" during the period when the upper arm switching element 18B is ON even in the V phase, and the V-phase voltage Vv becomes "H" during the period when the upper arm switching element 18B is ON, and the lower arm switching element 18F is OFF during the W phase. The W-phase voltage Vw becomes “H” during the period. The sum of the widths of the “H” periods is the magnitude of each phase voltage, and the U-phase voltage Vu is “large” and the V-phase voltage Vv and the W-phase voltage Vw are “medium” in the voltage vector V1.

Further, as is apparent from this figure, the phase voltage command calculation unit 33 synchronizes the switching timing (ON/OFF timing) of the switching element that sets each phase voltage to “H” even at the voltage vector V1, and the U phase voltage Vu. Of voltage command values Vu′, Vv′, and Vw′ that cancel the changes of V phase voltage Vv and W phase voltage Vw. As a result, even in the voltage vector V1, the neutral point potential Vc, which is the average of the phase voltages Vu, Vv, and Vw, is always constant and does not change, so that the common mode noise is eliminated.

(3-3) Voltage vector V1 (2)
Next, generation of another voltage vector V1 will be described with reference to FIG. Also in FIG. 5, the uppermost stage shows the U-phase voltage command value Vu′, the V-phase voltage command value Vv′, the W-phase voltage command value Vw′, and the triangular carriers X1 to X4, and the second stage from the top shows each switching element 18A. 18F ON/OFF state, the second stage from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the bottom stage shows the neutral point potential Vc of the motor 8. There is.

Similarly, on the right side, the directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing in the motor 8 are shown, but in the case of FIG. 5, the U-phase current iu flows into the motor 8. Direction, the V-phase current iv, and the W-phase current iw are in the direction of flowing out from the motor 8.

As described above, the phase voltage becomes “H” when the upper arm switching element is ON in the direction in which the phase current flows into the motor 8, and the lower arm switching element is ON in the direction in which the phase current flows out from the motor 8. The phase voltage becomes "H" when it is on. Therefore, when the U-phase current iu flows in the motor 8 and the V-phase current iv and the W-phase current iw flow out of the motor 8, switching is performed at the same timing as in FIG. 4 to generate the voltage vector V1. Then, since the V-phase current iv is directed to flow out from the motor 8, a current flows to the flywheel diode 31 connected to the upper arm switching element 18B during the dead time before the V-phase lower arm switching element 18E is turned on. 4 and the V-phase voltage Vv remains “H” as indicated by the broken line Z1 in FIG. 4, and the neutral point potential Vc fluctuates as indicated by the broken line Z2 in FIG. Become.

Therefore, in the case of the current direction as shown in FIG. 5, the phase voltage command calculation unit 33 causes the voltage command values Vu′, Vv′, Vw′ to switch the switching elements 18A to 18F at the timings shown in FIG. To generate. That is, in the case of FIG. 5, since the U-phase current iu flows into the motor 8 and the V-phase current iv and the W-phase current iw flow out of the motor 8, the upper arm switching element 18A is turned on in the U-phase. The U-phase voltage Vu becomes "H" during the V phase, the V-phase voltage Vv becomes "H" while the lower arm switching element 18E is OFF during the V phase, and the lower arm switching element 18F is OFF during the W phase. The W-phase voltage Vw becomes “H” during the period. The sum of the widths of the “H” periods is the magnitude of each phase voltage, and in this case as well, the voltage vector V1 is such that the U phase voltage Vu is “large” and the V phase voltage Vv and the W phase voltage Vw are “medium”. It becomes

In the voltage vector V1 in this case, the phase voltage command calculation unit 33 synchronizes the switching timing (ON/OFF timing) of the switching element that sets each phase voltage to “H” according to the direction of the phase current, and The change of the U-phase voltage Vu is changed to the voltage command values Vu′, Vv′, and Vw′ that are canceled by the change of the V-phase voltage Vv and the W-phase voltage Vw, and output. As a result, even in the direction of the current in this case, the neutral point potential Vc, which is the average of the phase voltages Vu, Vv, and Vw in the voltage vector V1, is always constant and does not change, so that common mode noise is eliminated. become.

(3-4) Voltage vector V2
Next, the generation of the voltage vector V2 in FIG. 2 will be described with reference to FIG. Also in FIG. 6, the uppermost stage shows the U-phase voltage command value Vu′, the V-phase voltage command value Vv′, the W-phase voltage command value Vw′ and the triangular carriers X1 to X4, and the second stage from the top shows each switching element 18A. 18F ON/OFF state, the second stage from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the bottom stage shows the neutral point potential Vc of the motor 8. There is.

Similarly, on the right side, the directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing in the motor 8 are shown. In the example of FIG. 6, the U-phase current iu and the V-phase current iv flow in the motor 8, the W-phase current iw flows out of the motor 8, or the U-phase current iu flows in the motor 8. , V-phase current iv and W-phase current iw are shown in the direction in which they flow out from the motor 8.

Also in this embodiment, when the U-phase current iu and the V-phase current iv flow in the motor 8 and the W-phase current iw flows in the motor 8, the upper arm switching element 18A is turned on in the U phase. The U-phase voltage Vu becomes "H" during the period when the upper arm switching element 18B is ON even in the V phase, and the V-phase voltage Vv becomes "H" during the period when the upper arm switching element 18B is ON, and the lower arm switching element 18F is OFF during the W phase. The W-phase voltage Vw becomes “H” during the period. When the U-phase current iu flows in the motor 8 and the V-phase current iv and the W-phase current iw flow in the motor 8, the upper arm switching element 18A is turned on in the U-phase. The U-phase voltage Vu is "H" during the V phase, the V-phase voltage Vv is "H" during the V phase while the lower arm switching element 18E is OFF, and the lower arm switching element 18F is OFF during the W phase. While the W-phase voltage Vw becomes “H” during the period, the V-phase voltage command value Vv′ is fixed at the maximum value, and therefore the V-phase voltage Vv does not change regardless of the direction of the current.

On the other hand, since the U-phase voltage command value Vu' and the W-phase voltage command value Vw' are fixed at low values, the U-phase voltage Vu and the W-phase voltage Vw change in a mutually canceling direction. .. The voltage vector V2 has a U-phase voltage Vu and a V-phase voltage Vv of “large” and a W-phase voltage Vw of “small”. As a result, even in the voltage vector V2, the neutral point potential Vc, which is the average of the phase voltages Vu, Vv, and Vw, is always constant and does not change, so that the common mode noise is eliminated.

(3-5) Voltage vector V3
Next, the generation of the voltage vector V3 shown in FIG. 2 will be described with reference to FIG. Also in FIG. 7, the uppermost stage shows the U-phase voltage command value Vu′, the V-phase voltage command value Vv′, the W-phase voltage command value Vw′ and the triangular carriers X1 to X4, and the second stage from the top shows each switching element 18A. 18F ON/OFF state, the second stage from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the bottom stage shows the neutral point potential Vc of the motor 8. There is.

Similarly, on the right side, the directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing in the motor 8 are shown. In the example of FIG. 7, the U-phase current iu and the V-phase current iv flow in the motor 8, the W-phase current iw flows out of the motor 8, or the U-phase current iu flows in the motor 8. , V-phase current iv and W-phase current iw are shown in the direction in which they flow out from the motor 8.

On the other hand, since the U-phase voltage command value Vu′ and the W-phase voltage command value Vw′ are fixed at medium values, the U-phase voltage Vu and the W-phase voltage Vw should change in a mutually canceling direction. become. The voltage vector V3 has a U-phase voltage Vu of “medium”, a V-phase voltage Vv of “large”, and a W-phase voltage Vw of “medium”. As a result, even in the voltage vector V3, the neutral point potential Vc, which is the average of the phase voltages Vu, Vv, and Vw, is always constant and does not change, so that the common mode noise is eliminated.

(3-6) Voltage vector V4
Next, generation of the voltage vector V4 of FIG. 2 will be described with reference to FIG. Also in FIG. 8, the uppermost stage shows the U-phase voltage command value Vu′, the V-phase voltage command value Vv′, the W-phase voltage command value Vw′, and the triangular carriers X1 to X4, and the second stage from the top shows each switching element 18A. 18F ON/OFF state, the second stage from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the bottom stage shows the neutral point potential Vc of the motor 8. There is.

In this embodiment, since the U-phase voltage command value Vu', the V-phase voltage command value Vv', and the W-phase voltage command value Vw' are all fixed at the highest values, the U-phase voltage Vu and the V-phase voltage Vv are irrespective of the direction of the current. , W-phase voltage Vw does not change. Then, the voltage vector V4 is such that the U-phase voltage Vu is “small” and the V-phase voltage Vv and the W-phase voltage Vw are “large”. Also in this case, the neutral point potential Vc, which is the average of the phase voltages Vu, Vv, and Vw, is always constant and does not change, so that the common mode noise is eliminated.

(3-7) Voltage vector V5
Next, generation of the voltage vector V5 of FIG. 2 will be described with reference to FIG. Also in FIG. 9, the uppermost stage shows the U-phase voltage command value Vu′, the V-phase voltage command value Vv′, the W-phase voltage command value Vw′, and the triangular carriers X1 to X4, and the second stage from the top shows each switching element 18A. 18F ON/OFF state, the second stage from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the bottom stage shows the neutral point potential Vc of the motor 8. There is.

Similarly, on the right side, the directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing in the motor 8 are shown. The example of FIG. 9 shows a case where the U-phase current iu and the V-phase current iv flow in the motor 8 and the W-phase current iw flows in the motor 8.

Also in this embodiment, when the U-phase current iu and the V-phase current iv flow in the motor 8 and the W-phase current iw flows in the motor 8, the upper arm switching element 18A is turned on in the U phase. The U-phase voltage Vu becomes "H" during the period when the upper arm switching element 18B is ON even in the V phase, and the V-phase voltage Vv becomes "H" during the period when the upper arm switching element 18B is ON, and the lower arm switching element 18F is OFF during the W phase. While the W-phase voltage Vw becomes “H” during the period, the W-phase voltage command value Vw′ is fixed at the maximum value, so that the W-phase voltage Vw does not change regardless of the direction of the current.

On the other hand, the U-phase voltage command value Vu' is fixed to a medium value, and the V-phase voltage command value Vv' is fixed to a medium value higher than the U-phase. These values are values in which the U-phase voltage Vu and the V-phase voltage Vw are synchronized with each other in consideration of the dead time and change in a direction in which they cancel each other. The voltage vector V5 has a U-phase voltage Vu of “medium”, a V-phase voltage Vv of “medium”, and a W-phase voltage Vw of “large”. As a result, even in the voltage vector V5, the neutral point potential Vc, which is the average of the phase voltages Vu, Vv, and Vw, is always constant and does not change, so that the common mode noise is eliminated.

(3-8) Voltage vector V6
Next, generation of the voltage vector V6 of FIG. 2 will be described with reference to FIG. Also in FIG. 10, the uppermost stage shows the U-phase voltage command value Vu′, the V-phase voltage command value Vv′, the W-phase voltage command value Vw′, and the triangular carriers X1 to X4, and the second stage from the top shows each switching element 18A. 18F ON/OFF state, the second stage from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the bottom stage shows the neutral point potential Vc of the motor 8. There is.

On the other hand, the U-phase voltage command value Vu' is fixed to a small value, and the V-phase voltage command value Vv' is a small value but fixed to a value higher than the U-phase. These values are values in which the U-phase voltage Vu and the V-phase voltage Vw are synchronized with each other in consideration of the dead time and change in a direction in which they cancel each other. The voltage vector V6 has a U-phase voltage Vu of “large”, a V-phase voltage Vv of “small”, and a W-phase voltage Vw of “large”. As a result, even in the voltage vector V6, the neutral point potential Vc, which is the average of the phase voltages Vu, Vv, and Vw, is always constant and does not change, so that the common mode noise is eliminated.

As described above in detail, in the present invention, the control device 21 synchronizes the switching timings of the upper and lower arm switching elements 18A to 18F for each phase, and changes the phase voltages Vu, Vv, Vw applied to the motor 8 to other values. Since the voltage command values Vu′, Vv′, and Vw′ that are canceled by the change in the phase voltage of are generated, the fluctuation of the neutral point potential Vc of the motor 8 is eliminated by the switching timing of the switching elements 18A to 18F. Alternatively, it becomes possible to remarkably suppress it. This makes it possible to effectively eliminate or suppress the occurrence of common mode noise.

Further, in the embodiment, the control device 21 synchronizes the switching timings of the upper and lower arm switching elements 18A to 18F according to the directions of the currents iu, iv, and iw flowing in the motor 8, and changes in the phase voltages Vu, Vv, Vw. , The voltage command values Vu′, Vv′, and Vw′ are changed so as to be canceled by the change in the other phase voltage, so that the fluctuation of the neutral point potential Vc can be eliminated without any problem regardless of the direction of the current flowing through the motor 8. Or, it becomes possible to suppress.

In the embodiment, the control device 21 turns on one of the lower arm switching elements (18D in the embodiment) of one phase and turns on the other upper arm switching elements of the two phases (18B and 18C in the embodiment). Since the specified section of switching is started from the state in which it is present, changes in each phase voltage Vu, Vv, Vw can be smoothly canceled by changes in other phase voltages.

Contrary to the embodiment, the control device 21 starts the specified section of switching from a state in which the lower arm switching element of any two phases is turned on and the upper arm switching element of another one phase is turned on. Even in this case, the change in each phase voltage Vu, Vv, Vw can be smoothly canceled by the change in the other phase voltage as in the embodiment.

Also, the delay time from the gate signal to the switching operation and the switching speed change depending on the magnitude of the flowing current and the characteristics of the switching element. Therefore, in order to eliminate or suppress the fluctuation of the neutral point potential Vc more accurately, the PWM signal generation unit 36 causes each of the half bridge circuits 19U to be different depending on the magnitude of the current flowing through the switching element and the characteristics of the switching element used. The output timing of the gate signal may be finely adjusted every 19W. The magnitude of the current flowing through the switching element used for the calculation for this fine adjustment can be obtained from the detected and estimated value of the current flowing through the motor 8.

Furthermore, the voltage vectors V0 to V6 shown in the embodiment are not limited to those, and can be changed without departing from the spirit of the present invention. Further, although the present invention is applied to the inverter device that drives and controls the motor of the electric compressor in the embodiment, the present invention is not limited to this, and the present invention is effective for drive control of the motor of various devices.

1 Inverter device 8 Motor 10 Upper arm power supply line 15 Lower arm power supply line 18A-18F Upper and lower arm switching element 19U U phase half bridge circuit 19V V phase half bridge circuit 19W W phase half bridge circuit 21

Control device

26A, 26B Current sensor 28 Three Phase inverter circuit 33 Phase voltage command calculator 36 PWM signal generator 37 Gate driver

Claims

An upper arm switching element and a lower arm switching element are connected in series for each phase between the upper arm power line and the lower arm power line, and the voltage at the connection point of the upper and lower arm switching elements for each phase is used as a three-phase AC output for the motor. An inverter circuit for applying to
In an inverter device comprising a control device for controlling switching of the upper and lower arm switching elements of each phase of the inverter circuit,
The said control apparatus synchronizes the switching timing of the upper-and-lower arm switching element of each said phase, and cancels the change of the phase voltage applied to the said motor by the change of another phase voltage, The inverter apparatus characterized by the above-mentioned.
The control device generates the voltage command value of each phase in which the switching timings of the upper and lower arm switching elements of each phase are synchronized, and the change in the phase voltage is canceled by the change in the other phase voltage. The inverter device according to claim 1, which controls an inverter circuit.
The control device synchronizes the switching timings of the upper and lower arm switching elements in accordance with the direction of the current flowing through the motor, and changes the phase voltage by canceling the change in the other phase voltage. The value is changed, The inverter apparatus of Claim 1 or Claim 2 characterized by the above-mentioned.
The control device starts a specified section of switching from a state in which the lower arm switching element of any one phase is turned on and the upper arm switching elements of the other two phases are turned on. The inverter device according to any one of claims 1 to 3.
The control device starts a specified section of switching from a state in which the lower arm switching element of any two phases is turned on and the upper arm switching element of another one phase is turned on. The inverter device according to any one of claims 1 to 3.