Inverter device

Abstract

The present invention provides an inverter device that can effectively eliminate or reduce common mode noise. The inverter device (1) includes: an inverter circuit (28) in which an upper bridge arm switching element (18A-18C) and a lower bridge arm switching element (18D-18F) are connected in series between an upper bridge arm power line (10) and a lower bridge arm power line (15) in each phase, and the voltage at the connection point of the upper and lower bridge arm switching elements of each phase is applied to the motor (8) as a three-phase AC output; and a control device (21). The control device synchronizes the switching timing of the upper and lower bridge arm switching elements of each phase, and uses the changes in the other phase voltages to offset the changes in the phase voltage applied to the motor.

Description

Technical Field

[0001] The present invention relates to an inverter device for driving a motor by applying an AC voltage to the motor using an inverter circuit. Background Art

[0002] Conventionally, in inverter devices for driving electric motors, a three-phase inverter circuit is formed using a plurality of switching elements, and PWM (Pulse Width Modulation) control is performed on the switching elements of each phase, UVW, so that a voltage waveform close to a sine wave is applied to the motor to drive it. However, common mode noise generated by changes in the neutral point potential of the motor becomes a problem.

[0003] For example, in the case of a motor constituting an electric compressor, the common mode noise is generated by a common mode current leaking through a parasitic capacitance between a housing of the compressor and the ground, but conventionally, a noise filter has been provided to satisfy the specification.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 4276097

[0007] Patent Document 2: Japanese Patent No. 5093452 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] However, the installation of the noise filter will lead to a larger device and a higher cost. On the other hand, the neutral point potential of the motor is obtained based on the average of the phase voltages, so the following method has been proposed: adjusting the change in phase voltage caused by the switching of the switching element to suppress the change in the neutral point potential of the motor (for example, refer to Patent Documents 1 and 2).

[0010] The present invention has been made in consideration of the above-mentioned existing situation, and an object of the present invention is to provide an inverter device that can effectively eliminate or suppress common mode noise.

[0011] Technical solutions adopted to solve technical problems

[0012] The inverter device of the first aspect of the present invention includes: an inverter circuit, in which an upper bridge arm switching element and a lower bridge arm switching element are connected in series between an upper bridge arm power line and a lower bridge arm power line in each phase, and the voltage at the connection point of the upper and lower bridge arm switching elements of each phase is applied to the motor as a three-phase AC output; and a control device, which controls the switching of the upper and lower bridge arm switching elements of each phase of the inverter circuit. The inverter device is characterized in that the control device synchronizes the switching timing of the upper and lower bridge arm switching elements of each phase, and uses the changes in other phase voltages to offset the changes in the phase voltage applied to the motor.

[0013] The inverter device of the second aspect of the present invention is characterized in that, in the above invention, the control device generates a voltage command value for each phase in which the switching timing of the upper and lower bridge arm switching elements of each phase is synchronized and the change of the phase voltage is offset by the change of other phase voltages to control the inverter circuit.

[0014] The inverter device of the third aspect of the present invention is characterized in that, in the above inventions, the control device changes the voltage command value so that the switching timing of the upper and lower bridge arm switching elements is synchronized according to the direction of the current flowing through the motor, and the change in phase voltage is offset by the change in other phase voltages.

[0015] The inverter device of the fourth aspect of the present invention is characterized in that in the above inventions, the control device starts the switching for a predetermined interval from a state in which the lower arm switching element of any phase is turned on and the upper arm switching elements of the other two phases are turned on.

[0016] The inverter device of the fifth aspect of the present invention is characterized in that, in the inventions of the first to third aspects of the present invention, the control device starts a specified switching interval from a state in which the lower arm switching elements of any two phases are turned on and the upper arm switching element of the other phase is turned on.

[0017] Effects of the Invention

[0018] According to the present invention, an inverter device includes: an inverter circuit, in which an upper bridge arm switching element and a lower bridge arm switching element are connected in series between an upper bridge arm power line and a lower bridge arm power line in each phase, and the voltage at the connection point of the upper and lower bridge arm switching elements of each phase is applied to the motor as a three-phase AC output; and a control device, which controls the switching of the upper and lower bridge arm switching elements of each phase of the inverter circuit. In the inverter device, the control device synchronizes the switching timing of the upper and lower bridge arm switching elements of each phase, and offsets the change of the phase voltage applied to the motor with the change of the other phase voltage, so that the change of the neutral point potential of the motor can be eliminated or significantly suppressed by the switching timing of the switching element. As a result, the generation of common mode noise can be effectively eliminated or suppressed.

[0019] In this case, as in the second aspect of the present invention, the control device actually generates voltage command values ​​for each phase so that the switching timings of the upper and lower arm switching elements of each phase are synchronized and the changes in phase voltage are offset by changes in other phase voltages to control the inverter circuit.

[0020] Here, the phase voltage in the dead time considered when switching the switching element changes according to the direction of the current flowing through the motor. Therefore, as in the third aspect of the present invention, if the control device changes the voltage command value so that the switching timing of the upper and lower bridge arm switching elements is synchronized according to the direction of the current flowing through the motor, and the change of the phase voltage is offset by the change of the other phase voltage, the change of the neutral point potential can be eliminated or suppressed without any obstacle regardless of the direction of the current flowing through the motor.

[0021] In addition, if, as in the fourth aspect of the invention, the control device starts the switching interval from the state where the lower bridge arm switching element of any phase is turned on and the upper bridge arm switching elements of the other two phases are turned on, or, as in the fifth aspect of the invention, the control device starts the switching interval from the state where the lower bridge arm switching elements of any two phases are turned on and the upper bridge arm switching element of the other phase is turned on, the changes in the phase voltage can be smoothly offset by the changes in the other phase voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a circuit diagram of an inverter device according to an embodiment of the present invention.

[0023] Figure 2 Yes Figure 1 A diagram showing a summary of voltage vectors V1 to V6 of the drive motor.

[0024] Figure 3 Yes Figure 1 A diagram for explaining generation of a voltage vector V0 performed by a control device of an inverter device.

[0025] Figure 4 Yes Figure 1 A diagram for explaining generation of a voltage vector V1 by a control device of an inverter device.

[0026] Figure 5 Yes Figure 1 A diagram for explaining generation of another voltage vector V1 performed by a control device of an inverter device.

[0027] Figure 6 Yes Figure 1 A diagram illustrating generation of a voltage vector V2 performed by a control device of an inverter device.

[0028] Figure 7 Yes Figure 1 A diagram for explaining generation of a voltage vector V3 performed by a control device of an inverter device.

[0029] Figure 8 Yes Figure 1 A diagram for explaining generation of a voltage vector V4 performed by a control device of an inverter device.

[0030] Fig. 9 Yes Figure 1 A diagram for explaining generation of a voltage vector V5 performed by a control device of an inverter device.

[0031] Fig.10 Yes Figure 1 A diagram for explaining generation of a voltage vector V6 performed by a control device of an inverter device. DETAILED DESCRIPTION

[0032] 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 an electric motor 8 , and the electric compressor constitutes a refrigerant circuit of a vehicle air conditioner, for example.

[0033] (1) Configuration of Inverter Device 1

[0034] Figure 1 In the embodiment, 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 the DC voltage of the DC power supply (vehicle battery: for example, 300V) 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 each phase half-bridge circuit 19U~19W has an upper arm switching element 18A~18C and a lower arm switching element 18D~18F. In addition, each switching element 18A~18F is respectively connected in reverse parallel with a freewheeling diode 31.

[0035] In addition, each of the switching elements 18A to 18F is constituted by an insulated gate bipolar transistor (IGBT) or the like in which a MOS structure is incorporated into a gate portion in the embodiment.

[0036] The upper end side of the upper arm switching elements 18A to 18C of the inverter circuit 28 is connected to the upper arm power supply line (positive side bus) 10 of the DC power supply 29 and the filter capacitor 32. On the other hand, the lower end side of the lower arm switching elements 18D to 18F of the inverter circuit 28 is connected to the DC power supply 29 and the lower arm power supply line (negative side bus) 15 of the filter capacitor 32.

[0037] 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, 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, and the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half-bridge circuit 19W are connected in series.

[0038] The connection point between the upper arm switch element 18A and the lower arm switch element 18D of the U-phase half-bridge circuit 19U is connected to the armature coil 2 of the U-phase of the motor 8, the connection point between the upper arm switch element 18B and the lower arm switch element 18E of the V-phase half-bridge circuit 19V is connected to the armature coil 3 of the V-phase of the motor 8, and the connection point between the upper arm switch element 18C and the lower arm switch element 18F of the W-phase half-bridge circuit 19W is connected to the armature coil 4 of the W-phase of the motor 8.

[0039] (2) Structure of the control device 21

[0040] The control device 21 is composed of a microcomputer having a processor, and in the embodiment, the rotation speed command value is input from the vehicle ECU, the 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 terminal of each switching element 18A to 18F is controlled.

[0041] The control device 21 of the embodiment has a phase voltage command operation unit 33, a PWM signal generation unit 36, a gate driver 37 and current sensors 26A, 26B, the current sensors 26A, 26B are composed of current transformers for measuring the motor current (phase current) flowing through each phase of the motor 8, namely, the U-phase current iu, the V-phase current iv, and the W-phase current iw, and each current sensor 26A, 26B is connected to the phase voltage command operation unit 33. In addition, the current sensor 26A measures the U-phase current iu, and the current sensor 26B measures the V-phase current iv. The W-phase current iw is calculated based on the above-mentioned U-phase current iu and V-phase current iv. In addition, in addition to measuring the motor current of each phase by the current sensors 26A, 26B as in the embodiment, there is no particular limitation on the method of detecting / estimating the current of each phase, such as detecting the current value of the lower arm power supply line 15 and estimating it by the phase voltage command operation unit 33 based on the current value and the operating state of the motor 8.

[0042] The phase voltage command calculation unit 33 calculates and generates three-phase modulated voltage command values ​​Vu' (hereinafter referred to as U-phase voltage command value Vu'), Vv' (hereinafter referred to as V-phase voltage command value Vv'), and Vw' (hereinafter referred to as W-phase voltage command value Vw'). The above-mentioned three-phase modulated voltage command values ​​are used to generate U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw applied to the armature coils 2 to 4 of each phase of the motor 8 based on the electrical angle, current command value and phase current of the motor 8.

[0043] The PWM signal generating unit 36 ​​compares the three-phase modulation voltage command values ​​Vu', Vv', Vw' calculated by the phase voltage command calculating unit 33 with the size of the triangular carrier (carrier triangular wave), thereby generating a PWM signal which serves as a driving command signal for the U-phase half-bridge circuit 19U, the V-phase half-bridge circuit 19V, and the W-phase half-bridge circuit 19W of the inverter circuit 28.

[0044] The gate driver 37 generates the gate voltage of the upper arm switch element 18A and the lower arm switch element 18D of the U-phase half-bridge circuit 19U, the gate voltage of the upper arm switch element 18B and the lower arm switch element 18E of the V-phase half-bridge circuit 19V, and the gate voltage of the upper arm switch element 18C and the lower arm switch element 18F of the W-phase half-bridge circuit 19W based on the PWM signal output from the PWM signal generating unit 36.

[0045] Then, each switching element 18A to 18F of the inverter circuit 28 is driven to be turned on / off based on the gate voltage output from the gate driver 37. That is, if the gate voltage becomes the on state (predetermined voltage value), the switching element is turned on, and if the gate voltage becomes the off state (zero), the switching element is turned off. In the case where the switching elements 18A to 18F are the above-mentioned IGBTs, the gate driver 37 is a circuit for applying the gate voltage to the IGBT based on the PWM signal, and is composed of a photocoupler, a logic IC, a transistor, etc.

[0046] 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) as the U-phase voltage Vu (phase voltage) to the armature coil 2 of the U-phase of the motor 8, 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) as the V-phase voltage Vv (phase voltage) to the armature coil 3 of the V-phase of the motor 8, and 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) as the W-phase voltage Vw (phase voltage) to the armature coil 4 of the W-phase of the motor 8.

[0047] (3) Operation of the control device 21

[0048] Next, refer to Figure 2 to Figure 10 The actual control action of the control device 21 is described below. The phase voltage command calculation unit 33 of the control device 21 of the inverter device 1 of the present invention calculates the U-phase voltage command value Vu', the V-phase voltage command value Vv' and the W-phase voltage command value Vw' (three-phase modulation voltage command value) to eliminate the change of the neutral point potential Vc of the motor 8 and generate the voltage vectors V0 to V6 (summarized in Figure 2 Then, any one of the voltage vectors V0 to V6 is selected according to the above-mentioned rotation speed command value to operate the motor 8.

[0049] (3-1) Voltage vector V0

[0050] First, use Figure 3 To illustrate Figure 2 Generation of the voltage vector V0. Figure 3 The top part shows the U-phase voltage command value Vu', V-phase voltage command value Vv', W-phase voltage command value Vw' and triangular carriers X1~X4 generated by the phase voltage command calculation unit 33 of the control device 21, the second part from the top shows the on / off state of each switching element 18A~18F, the second part 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 part shows the neutral point potential Vc of the motor 8.

[0051] The right side shows the directions of U-phase current iu, V-phase current iv, and W-phase current iw flowing through the motor 8. There are six combinations of directions of the phase currents, with the direction flowing into the motor 8 indicated by + and the direction flowing out of the motor 8 indicated by -. Figure 3 The example is the uppermost case, showing a 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 .

[0052] In addition, in the embodiment, in order to generate the dead time, the triangular carrier wave is composed of two uplinks X1 and X2 and two downlinks X3 and X4. The phase of the uplink X2 is ahead of the phase of the uplink X1, and the phase of the downlink X4 is ahead of the phase of the downlink X3. Then, in the first half of one carrier cycle, the PWM signal generating unit 36 ​​compares the uplink X1 of the triangular carrier wave with each voltage command value Vu', Vv', and Vw' to generate a PWM signal for turning on / off the lower arm switching element 18D of the U phase, the upper arm switching element 18B of the V phase, and the upper arm switching element 18C of the W phase, and compares the uplink X2 of the triangular carrier wave with each voltage command value Vu', Vv', and Vw' to generate a PWM signal for turning on / off the upper arm switching element 18A of the U phase, the lower arm switching element 18E of the V phase, and the lower arm switching element 18F of the W phase.

[0053] In the second half of one carrier cycle, the PWM signal generating unit 36 ​​compares the downlink X3 of the triangular carrier with each voltage command value Vu', Vv', Vw' to generate a PWM signal for turning on / off the upper arm switching element 18A of the U phase, the lower arm switching element 18E of the V phase, and the lower arm switching element 18F of the W phase, and compares the downlink X4 of the triangular carrier with each voltage command value Vu', Vv', Vw' to generate a PWM signal for turning on / off the lower arm switching element 18D of the U phase, the upper arm switching element 18B of the V phase, and the upper arm switching element 18C of the W phase.

[0054] In the embodiment, the phase voltage command calculation unit 33 starts the switching for the predetermined interval from the state where the lower arm switching element 18D of the U phase is turned on and the upper arm switching element 18B of the V phase and the upper arm switching element 18C of the W phase are turned on.

[0055] As in the embodiment, when 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 U-phase voltage Vu becomes "H" during the period when the upper arm switching element 18A is turned on in the U-phase, the V-phase voltage Vv also becomes "H" during the period when the upper arm switching element 18B is turned on in the V-phase, and the W-phase voltage Vw becomes "H" during the period when the lower arm switching element 18F is turned off in the W-phase. The sum of the widths of the "H" period becomes the magnitude of the voltage of each phase, and in the voltage vector V0, all three phases become "medium" magnitudes.

[0056] In addition, as is clear from the 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 generates voltage command values ​​Vu', Vv', and Vw' that cancel the change of the U phase voltage Vu by the change of the V phase voltage Vv and the W phase voltage Vw. As a result, the average of the phase voltages Vu, Vv, and Vw, that is, the neutral point potential Vc, is always constant and does not change, so common mode noise is eliminated.

[0057] (3-2) Voltage vector V1 (part 1)

[0058] Next, use Figure 4 To illustrate Figure 2 Generation of the voltage vector V1. Figure 4 In the figure, the uppermost part also 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~X4, the second part from the top shows the on / off state of each switching element 18A~18F, the second part from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the lowermost part shows the neutral point potential Vc of the motor 8.

[0059] Furthermore, similarly, the right side shows the directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing through the motor 8. Figure 4 The example of is also the uppermost case, showing a 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.

[0060] In addition, the operation of the PWM signal generating unit 36 ​​is the same as described above. In addition, similarly, in the embodiment, the phase voltage command calculation unit 33 starts the switching for a predetermined interval from the state where the lower bridge arm switching element 18D of the U phase is turned on, and the upper bridge arm switching element 18B of the V phase and the upper bridge arm switching element 18C of the W phase are turned on.

[0061] As in the embodiment, when the U-phase current iu and the V-phase current iv are flowing into the motor 8 and the W-phase current iw is flowing out of the motor 8, the U-phase voltage Vu becomes "H" during the period when the upper arm switching element 18A is turned on in the U-phase, the V-phase voltage Vv also becomes "H" during the period when the upper arm switching element 18B is turned on in the V-phase, and the W-phase voltage Vw becomes "H" during the period when the lower arm switching element 18F is turned off in the W-phase. The sum of the widths of the "H" period becomes 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" magnitudes in the voltage vector V1.

[0062] As is clear from the figure, even in the case of the voltage vector V1, 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 generates voltage command values ​​Vu', Vv', and Vw' that cancel the change in the U phase voltage Vu by the change in the V phase voltage Vv and the W phase voltage Vw. Thus, even in the case of the voltage vector V1, the average of the phase voltages Vu, Vv, and Vw, that is, the neutral point potential Vc, is always constant and does not change, so that common mode noise is eliminated.

[0063] (3-3) Voltage vector V1 (Part 2)

[0064] Next, use Figure 5 Let's explain the generation of another voltage vector V1. Figure 5 In the figure, the uppermost part also 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~X4, the second part from the top shows the on / off state of each switching element 18A~18F, the second part from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the lowermost part shows the neutral point potential Vc of the motor 8.

[0065] In addition, similarly, 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 shown on the right side, but Figure 5 In the case of , 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 .

[0066] In addition, the operation of the PWM signal generating unit 36 ​​is the same as described above. In addition, similarly, in the embodiment, the phase voltage command calculation unit 33 starts the switching for a predetermined interval from the state where the lower bridge arm switching element 18D of the U phase is turned on, and the upper bridge arm switching element 18B of the V phase and the upper bridge arm switching element 18C of the W phase are turned on.

[0067] As described above, when the upper arm switching element is turned on in the direction in which the phase current flows into the motor 8, the phase voltage becomes "H", and when the lower arm switching element is turned on in the direction in which the phase current flows out of the motor 8, the phase voltage becomes "H". Therefore, when 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, if the phase current iu flows into the motor 8, the V-phase current iv and the W-phase current iw flow out of the motor 8, the phase voltage becomes "H". Figure 4 The same timing is used to switch to generate the voltage vector V1. Since the V-phase current iv flows from the motor 8, the current flows through the freewheeling diode 31 connected to the upper-arm switching element 18B in the dead zone before the lower-arm switching element 18E of the V-phase is turned on. Figure 4 As shown by the dashed line Z1 in the middle, the V-phase voltage Vv is kept at "H", and Figure 4 As shown by the middle dotted line Z2, the neutral point potential Vc changes.

[0068] Therefore, in Figure 5 In the case of the current direction, the phase voltage command calculation unit 33 Figure 5 The voltage command values ​​Vu', Vv', and Vw' for switching the switching elements 18A to 18F are generated at such timing. Figure 5 In the case of , 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. Therefore, in the U-phase, the U-phase voltage Vu becomes "H" during the period when the upper arm switching element 18A is turned on, in the V-phase, the V-phase voltage Vv becomes "H" during the period when the lower arm switching element 18E is turned off, and in the W-phase, the W-phase voltage Vw also becomes "H" during the period when the lower arm switching element 18F is turned off. The sum of the widths of the "H" period becomes the magnitude of each phase voltage. In this case, the voltage vector V1 also becomes a magnitude in which the U-phase voltage Vu is "large" and the V-phase voltage Vv and the W-phase voltage Vw are "medium".

[0069] Then, according to the direction of the phase current 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", and changes to the voltage command values ​​Vu', Vv', and Vw' that cancel the change of the U phase voltage Vu by the change of the V phase voltage Vv and the W phase voltage Vw, and outputs them. As a result, even in the direction of the current in this case, the average of the phase voltages Vu, Vv, and Vw in the voltage vector V1, that is, the neutral point potential Vc, is always constant and does not change, so the common mode noise is eliminated.

[0070] (3-4) Voltage vector V2

[0071] Next, use Figure 6 To illustrate Figure 2 Generation of the voltage vector V2. Figure 6 In the figure, the uppermost part also 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~X4, the second part from the top shows the on / off state of each switching element 18A~18F, the second part from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the lowermost part shows the neutral point potential Vc of the motor 8.

[0072] Furthermore, similarly, the right side shows the directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing through the motor 8. Figure 6 The example shows the following situation: the U-phase current iu and the V-phase current iv are in the direction of flowing into the motor 8, and the W-phase current iw is in the direction of flowing out of the motor 8, or the U-phase current iu is in the direction of flowing into the motor 8, and the V-phase current iv and the W-phase current iw are in the direction of flowing out of the motor 8.

[0073] In addition, the operation of the PWM signal generating unit 36 ​​is the same as described above. In addition, similarly, in the embodiment, the phase voltage command calculation unit 33 starts the switching for a predetermined interval from the state where the lower bridge arm switching element 18D of the U phase is turned on, and the upper bridge arm switching element 18B of the V phase and the upper bridge arm switching element 18C of the W phase are turned on.

[0074] In the present embodiment, when the U-phase current iu and the V-phase current iv are flowing into the motor 8 and the W-phase current iw is flowing out of the motor 8, in the U-phase, the U-phase voltage Vu becomes "H" while the upper arm switch element 18A is turned on, and in the V-phase, the V-phase voltage Vv also becomes "H" while the upper arm switch element 18B is turned on, and in the W-phase, the W-phase voltage Vw becomes "H" while the lower arm switch element 18F is turned off. In addition, when the U-phase current iu is flowing into the motor 8 and the V-phase current iv and the W-phase current iw are flowing out of the motor 8, in the U-phase, the U-phase voltage Vu becomes "H" during the period when the upper bridge arm switching element 18A is turned on, and in the V-phase, the V-phase voltage Vv becomes "H" during the period when the lower bridge arm switching element 18E is turned off, and in the W-phase, the W-phase voltage Vw also becomes "H" during the period when the lower bridge arm switching element 18F is turned off, but the V-phase voltage command value Vv' is fixed at the maximum value, so regardless of the direction of the current, the V-phase voltage Vv does not change.

[0075] On the other hand, the U-phase voltage command value Vu' and the W-phase voltage command value Vw' are fixed at low values, so the U-phase voltage Vu and the W-phase voltage Vw are synchronized and change in the direction of canceling each other. In addition, the voltage vector V2 becomes a size in which the U-phase voltage Vu and the V-phase voltage Vv are "large" and the W-phase voltage Vw is "small". Therefore, even in the voltage vector V2, the average of the phase voltages Vu, Vv, and Vw, that is, the neutral point potential Vc, is always constant and does not change, so the common mode noise is eliminated.

[0076] (3-5) Voltage vector V3

[0077] Next, use Figure 7 To illustrate Figure 2 Generation of voltage vector V3. Figure 7 In the figure, the uppermost part also 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~X4, the second part from the top shows the on / off state of each switching element 18A~18F, the second part from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the lowermost part shows the neutral point potential Vc of the motor 8.

[0078] Furthermore, similarly, the right side shows the directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing through the motor 8. Figure 7 The example shows the following situation: the U-phase current iu and the V-phase current iv are in the direction of flowing into the motor 8, and the W-phase current iw is in the direction of flowing out of the motor 8, or the U-phase current iu is in the direction of flowing into the motor 8, and the V-phase current iv and the W-phase current iw are in the direction of flowing out of the motor 8.

[0079] In addition, the operation of the PWM signal generating unit 36 ​​is the same as described above. In addition, similarly, in the embodiment, the phase voltage command calculation unit 33 starts the switching for a predetermined interval from the state where the lower bridge arm switching element 18D of the U phase is turned on, and the upper bridge arm switching element 18B of the V phase and the upper bridge arm switching element 18C of the W phase are turned on.

[0080] In the present embodiment, when the U-phase current iu and the V-phase current iv are flowing into the motor 8 and the W-phase current iw is flowing out of the motor 8, in the U-phase, the U-phase voltage Vu becomes "H" while the upper arm switch element 18A is turned on, and in the V-phase, the V-phase voltage Vv also becomes "H" while the upper arm switch element 18B is turned on, and in the W-phase, the W-phase voltage Vw becomes "H" while the lower arm switch element 18F is turned off. In addition, when the U-phase current iu is flowing into the motor 8 and the V-phase current iv and the W-phase current iw are flowing out of the motor 8, in the U-phase, the U-phase voltage Vu becomes "H" during the period when the upper bridge arm switching element 18A is turned on, and in the V-phase, the V-phase voltage Vv becomes "H" during the period when the lower bridge arm switching element 18E is turned off, and in the W-phase, the W-phase voltage Vw also becomes "H" during the period when the lower bridge arm switching element 18F is turned off, but the V-phase voltage command value Vv' is fixed at the maximum value, so regardless of the direction of the current, the V-phase voltage Vv does not change.

[0081] On the other hand, the U-phase voltage command value Vu' and the W-phase voltage command value Vw' are fixed at medium values, so the U-phase voltage Vu and the W-phase voltage Vw are synchronized and change in the direction of canceling each other. In addition, the voltage vector V3 becomes the size of the U-phase voltage Vu being "medium", the V-phase voltage Vv being "large", and the W-phase voltage Vw being "medium". Therefore, even with the voltage vector V3, the average of the phase voltages Vu, Vv, and Vw, that is, the neutral point potential Vc, is always constant and does not change, so the common mode noise is eliminated.

[0082] (3-6) Voltage vector V4

[0083] Next, use Figure 8 To illustrate Figure 2 Generation of voltage vector V4. Figure 8 In the figure, the uppermost part also 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~X4, the second part from the top shows the on / off state of each switching element 18A~18F, the second part from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the lowermost part shows the neutral point potential Vc of the motor 8.

[0084] In addition, the operation of the PWM signal generating unit 36 ​​is the same as described above. In addition, similarly, in the embodiment, the phase voltage command calculation unit 33 starts the switching for a predetermined interval from the state where the lower bridge arm switching element 18D of the U phase is turned on, and the upper bridge arm switching element 18B of the V phase and the upper bridge arm switching element 18C of the W phase are turned on.

[0085] In this embodiment, 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 maximum value. Therefore, regardless of the direction of the current, the U-phase voltage Vu, the V-phase voltage Vv, and the W-phase voltage Vw do not change. The voltage vector V4 becomes a size in which the U-phase voltage Vu is "small" and the V-phase voltage Vv and the W-phase voltage Vw are "large". In this case, the average of the phase voltages Vu, Vv, and Vw, that is, the neutral point potential Vc, is always constant and does not change, so the common mode noise is eliminated.

[0086] (3-7) Voltage vector V5

[0087] Next, use Fig. 9 To illustrate Figure 2 Generation of the voltage vector V5. Fig. 9 In the figure, the uppermost part also 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~X4, the second part from the top shows the on / off state of each switching element 18A~18F, the second part from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the lowermost part shows the neutral point potential Vc of the motor 8.

[0088] Furthermore, similarly, the right side shows the directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing through the motor 8. Fig. 9 The example shows a 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 .

[0089] In addition, the operation of the PWM signal generating unit 36 ​​is the same as described above. In addition, similarly, in the embodiment, the phase voltage command calculation unit 33 starts the switching for a predetermined interval from the state where the lower bridge arm switching element 18D of the U phase is turned on, and the upper bridge arm switching element 18B of the V phase and the upper bridge arm switching element 18C of the W phase are turned on.

[0090] In the present embodiment, when the U-phase current iu and the V-phase current iv are flowing into the motor 8 and the W-phase current iw is flowing out of the motor 8, in the U-phase, the U-phase voltage Vu becomes "H" while the upper arm switch element 18A is turned on, and in the V-phase, the V-phase voltage Vv also becomes "H" while the upper arm switch element 18B is turned on, and in the W-phase, the W-phase voltage Vw becomes "H" while the lower arm switch element 18F is turned off, but the W-phase voltage command value Vw' is fixed at the maximum value, so the W-phase voltage Vw does not change regardless of the direction of the current.

[0091] On the other hand, the U-phase voltage command value Vu' is fixed at a medium value, and the V-phase voltage command value Vv' is fixed at a medium value higher than the U-phase. These values ​​are set to values ​​that are synchronized with the V-phase voltage Vw and change in the direction of canceling each other when considering the dead time. In addition, the voltage vector V5 becomes a size in which the U-phase voltage Vu is "medium", the V-phase voltage Vv is "medium", and the W-phase voltage Vw is "large". Therefore, even with the voltage vector V5, the average of the phase voltages Vu, Vv, and Vw, that is, the neutral point potential Vc, is always constant and does not change, so the common mode noise is eliminated.

[0092] (3-8) Voltage vector V6

[0093] Next, use Fig.10 To illustrate Figure 2 Generation of the voltage vector V6. Fig.10 In the figure, the uppermost part also 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~X4, the second part from the top shows the on / off state of each switching element 18A~18F, the second part from the bottom shows the U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw applied to the motor 8, and the lowermost part shows the neutral point potential Vc of the motor 8.

[0094] Furthermore, similarly, the right side shows the directions of the U-phase current iu, the V-phase current iv, and the W-phase current iw flowing through the motor 8. Fig. 9 The example shows a 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 .

[0095] In addition, the operation of the PWM signal generating unit 36 ​​is the same as described above. In addition, similarly, in the embodiment, the phase voltage command calculation unit 33 starts the switching for a predetermined interval from the state where the lower bridge arm switching element 18D of the U phase is turned on, and the upper bridge arm switching element 18B of the V phase and the upper bridge arm switching element 18C of the W phase are turned on.

[0096] In the present embodiment, when the U-phase current iu and the V-phase current iv are flowing into the motor 8 and the W-phase current iw is flowing out of the motor 8, in the U-phase, the U-phase voltage Vu becomes "H" while the upper arm switch element 18A is turned on, and in the V-phase, the V-phase voltage Vv also becomes "H" while the upper arm switch element 18B is turned on, and in the W-phase, the W-phase voltage Vw becomes "H" while the lower arm switch element 18F is turned off, but the W-phase voltage command value Vw' is fixed at the maximum value, so the W-phase voltage Vw does not change regardless of the direction of the current.

[0097] On the other hand, the U-phase voltage command value Vu' is fixed at a smaller value, and the V-phase voltage command value Vv' is a smaller value, but fixed at a higher value than the U-phase. These values ​​are set to values ​​that are synchronized with the V-phase voltage Vw and change in the direction of canceling each other when considering the dead time. In addition, the voltage vector V6 becomes a size in which the U-phase voltage Vu is "large", the V-phase voltage Vv is "small", and the W-phase voltage Vw is "large". Therefore, even in the case of the voltage vector V6, the average of the phase voltages Vu, Vv, and Vw, that is, the neutral point potential Vc, is always constant and does not change, so the common mode noise is eliminated.

[0098] As described in detail above, in the present invention, the control device 21 synchronizes the switching timing of the upper and lower arm switching elements 18A to 18F of each phase, and generates voltage command values ​​Vu', Vv', and Vw' that cancel the changes in the phase voltages Vu, Vv, and Vw applied to the motor 8 by the changes in the other phase voltages. Therefore, the change in the neutral point potential Vc of the motor 8 can be eliminated or significantly suppressed by the switching timing of the switching elements 18A to 18F. As a result, the generation of common mode noise can be effectively eliminated or suppressed.

[0099] In addition, in the embodiment, the control device 21 changes the voltage command values ​​Vu', Vv', Vw' so that the switching timing of the upper and lower bridge arm switching elements 18A~18F is synchronized according to the direction of the current iu, iv, iw flowing through the motor 8, and the changes in the phase voltages Vu, Vv, Vw are offset by the changes in other phase voltages. Therefore, regardless of the direction of the current flowing through the motor 8, the change in the neutral point potential Vc can be eliminated or suppressed without hindrance.

[0100] In addition, in the embodiment, the control device 21 starts the switching interval from the state where the lower bridge arm switching element of any phase (in the embodiment, 18D) is turned on and the upper bridge arm switching elements of the other two phases (in the embodiment, 18B and 18C) are turned on. Therefore, the changes in the voltages of other phases can be used to smoothly offset the changes in the voltages Vu, Vv, and Vw of each phase.

[0101] In addition, contrary to the embodiment, even if the control device 21 starts the switching interval from the state where the lower arm switching elements of any two phases are turned on and the upper arm switching element of the other phase is turned on, the changes in the voltages of each phase Vu, Vv, and Vw can be smoothly offset by the changes in the voltages of other phases, as in the embodiment.

[0102] In addition, the delay time from the gate signal to the switching operation and the switching speed vary according to the magnitude of the current flowing and the characteristics of the switching element. Therefore, in order to more accurately eliminate or suppress the change of the neutral point potential Vc, the PWM signal generation unit 36 ​​can fine-tune the output timing of the gate signal for each of the half-bridge circuits 19U to 19W according to the magnitude of the current flowing through the switching element and the characteristics of the switching element used. The magnitude of the current flowing through the switching element used in the calculation for this fine adjustment can be obtained by detecting and estimating the value of the current flowing through the motor 8.

[0103] In addition, the voltage vectors V0 to V6 shown in the embodiment are not limited thereto, and can be changed within the scope of the present invention. In addition, in the embodiment, the present invention is applied to an inverter device for driving and controlling the motor of an electric compressor, but it is not limited thereto, and the present invention is effective in driving and controlling the motors of various devices.

[0104] Description of symbols

[0105] 1Inverter device

[0106] 8 Electric Motor

[0107] 10 Upper bridge arm power line

[0108] 15 Lower bridge arm power line

[0109] 18A~18F Upper and lower bridge switch elements

[0110] 19U U-phase half-bridge circuit

[0111] 19V V-phase half-bridge circuit

[0112] 19W W-phase half-bridge circuit

[0113] 21 Control device

[0114] 26A, 26B Current Sensor

[0115] 28 Three-phase inverter circuit

[0116] 33-phase voltage command calculation unit

[0117] 36PWM signal generation unit

[0118] 37Gate Driver

Claims

1. An inverter device, comprising: An inverter circuit in which an upper bridge arm switching element and a lower bridge arm switching element are connected in series between an upper bridge arm power line and a lower bridge arm power line in each phase, and a voltage at a connection point of the upper and lower bridge arm switching elements of each phase is applied to the motor as a three-phase AC output; as well as A control device, which controls the switching of the upper and lower bridge arm switching elements of each phase of the inverter circuit, wherein the inverter device is characterized in that: The control device generates a switch timing synchronization for the upper and lower bridge arm switch elements of each phase, The inverter circuit is controlled by using the voltage command value of each phase so that a change in the phase voltage applied to the motor is offset by a change in the voltage of another phase. The control device changes the voltage command value according to whether the current flowing through the respective phases of the motor flows into the motor or flows out of the motor.

2. The inverter device according to claim 1, characterized in that: The control device starts a switching period in a predetermined 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.

3. The inverter device according to claim 1, characterized in that: The control device starts a switching period for a predetermined period from a state in which the lower arm switching elements of any two phases are turned on and the upper arm switching element of the other one phase is turned on.

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