Inverter device

Abstract

The present application provides an inverter device that is based on two-phase modulation and that strives to further reduce common-mode noise. A control device (21) has a phase voltage command calculation section (33) that calculates three-phase modulation voltage command values, an interline modulation calculation section (34) that calculates two-phase modulation voltage command values that fix the on / off states of the switching elements of one phase of an inverter circuit (28) and that modulate the on / off states of the switching elements of the other two phases, and a PWM signal generation section (36) that PWM-controls the inverter circuit, synchronizes the switching timings of the switching elements of the two phases whose on / off states are modulated, and offsets the changes in the phase voltages applied to the motor (8) with changes in the other phase voltages.

Description

Technical Field

[0001] This invention relates to an inverter device that applies a three-phase AC output to and drives a motor through an inverter circuit. Background Technology

[0002] Previously, inverter devices used to drive motors used multiple switching elements to form a three-phase inverter circuit, and PWM (Pulse Width Modulation) control was applied to the switching elements of each phase (UVW) to apply a near-sinusoidal voltage waveform to drive the motor. However, common-mode noise caused by the fluctuation of the neutral point potential of the motor became a problem.

[0003] For example, in the case of the electric motor constituting an electric compressor, the common-mode noise is generated by the common-mode current leaking through the parasitic capacitance between the compressor casing and ground, which has traditionally been met by installing noise filters. However, installing such noise filters leads to larger device sizes and increased costs.

[0004] In response, the following method is proposed: by correcting the three-phase modulation voltage command values ​​(U-phase voltage command value Vu', V-phase voltage command value Vv', and W-phase voltage command value Vw') to match the switching timing of the upper and lower arm switching elements of each phase, thereby eliminating the generation of common-mode noise caused by the fluctuation of the neutral point potential (for example, see Patent Document 1).

[0005] then, Figure 10 This diagram illustrates the following parameters in the inverter device described above: the U-phase voltage command correction value Cu' (corrected for the U-phase voltage command value Vu'), the V-phase voltage command correction value Cv' (corrected for the V-phase voltage command value Vv'), the W-phase voltage command correction value Cw' (corrected for the W-phase voltage command value Vw'), the carrier signal, the phase voltages (PWM signals) of the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw, and the neutral point potential Vc of the motor. Additionally, Figure 10 Each value is a value normalized (corrected to -1 to 1) to the DC voltage Vdc.

[0006] In this scenario, due to the use of a sawtooth wave carrier signal (solid line), the U-phase voltage command correction value Cu' has a rising command value Cu'up (thin dashed line, same below) and a falling command value Cu'down (wide dashed line, same below) within one carrier cycle. Similarly, the V-phase voltage command correction value Cv' also has a rising command value Cv'up and a falling command value Cv'down within one carrier cycle, and the W-phase voltage command correction value Cw' also has a rising command value Cw'up and a falling command value Cw'down within one carrier cycle.

[0007] Then, by comparing the rising command value Cu'up and falling command value Cu'down of the U-phase voltage command correction value Cu', the rising command value Cv'up and falling command value Cv'down of the V-phase voltage command correction value Cv', the rising command value Cw'up and falling command value Cw'down of the W-phase voltage command correction value Cw', and the magnitude of the carrier signal, a PWM signal is generated as the drive command signal for the inverter circuit. This PWM signal is the normalized phase voltages of the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw.

[0008] Then, the neutral point potential Vc of the motor is calculated by the average value of each phase voltage (Vu+Vv+Vw) / 3, as in the method of Patent Document 1, such as Figure 11 As shown, the switching timing of the upper and lower arm switching elements of each phase is synchronized by voltage command correction values ​​Cu', Cv', and Cw', and the changes in the phase voltage of other phases are used to offset the changes in the phase voltage applied to the motor, thereby suppressing the fluctuation of the neutral point potential Vc. Furthermore, Figure 11 yes Figure 10 An enlarged view of section Z1. Furthermore, the conditions at this time are, for example, a carrier frequency of 20kHz and a DC voltage of 350V. Also, in each figure, to compare the variation in the neutral point potential Vc using integers, it is represented by Vc = (Vu + Vv + Vw) instead of an average value.

[0009] In addition, such as Figure 11 As shown, the specified switching range begins when the upper arm switching element of phase U is turned on, and the lower arm switching elements of phases V and W are turned on. For example, in Figure 11 Phases t9 (45°) and t11 (slightly past 52°) generate a rise command value Cu'up, causing the V-phase voltage Vv to rise in a timing match with the U-phase voltage Vu's decline. Conversely, phases t10 (46.5°) and t12 (slightly before 54°) generate a fall command value Cw'down, causing the W-phase voltage Vw to fall in a timing match with the U-phase voltage Vu's rise. Thus, the variation in the neutral point potential Vc at each phase t9 to t12 is eliminated. Furthermore, the variation range of the neutral point potential Vc is -1 to 1 / 2 (…). Figure 10 , Figure 11 ).

[0010] Therefore, the common-mode noise generated in one carrier cycle can theoretically be reduced to 1 / 3. Figure 12 The spectrum (FFT result) of the neutral point potential in the inverter device described above is shown. Figure 13The figures show the spectrum of the neutral point potential in a typical three-phase modulation inverter. It is clear from the figures that, according to the above method, the variation of the neutral point potential Vc is suppressed compared to typical three-phase modulation.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: WO2019 / 180763A1

[0014] Patent Document 2: Japanese Patent Application Publication No. 2019-115158 Summary of the Invention

[0015] The technical problem that the invention aims to solve

[0016] However, when the rising timing of the V-phase voltage and the falling timing of the W-phase voltage are matched to the falling timing (t9, t11) and rising timing (t10, t12) of the U-phase voltage respectively, as described above, the modulation amplitude becomes narrow and a high modulation rate cannot be achieved, resulting in a problem that the area that the motor can drive becomes very narrow.

[0017] In recent years, to reduce losses and heat generation from switching elements, an inverter device employing a method known as two-phase modulation has been proposed. This two-phase modulation inverter device controls the switching by fixing the on / off state of any one phase of the UVW circuit while modulating the on / off states of the other two phases. Compared to three-phase modulation, this reduces the number of switching operations, thus reducing switching losses and heat generation, while simultaneously performing PWM control (see, for example, Patent Document 2). Furthermore, because the number of switching operations is reduced, the number of neutral point potential fluctuations naturally decreases, thereby reliably reducing common-mode noise to 2 / 3.

[0018] Figure 14 U, V, and W represent the two-phase modulated voltage command values ​​generated from the three-phase modulated voltage command values ​​(U-phase voltage command value Vu', V-phase voltage command value Vv', and W-phase voltage command value Vw') in a typical two-phase modulation inverter device, namely, the U-phase voltage command value, the V-phase voltage command value, and the W-phase voltage command value. Furthermore, in this case, each value is also normalized (corrected to -1 to 1) using the DC voltage Vdc.

[0019] Furthermore, in this case, since a sawtooth wave carrier signal (solid line) is also used, the biphase modulated U-phase voltage command value U has a rising command value Uup and a falling command value Udown within one carrier cycle. Similarly, the biphase modulated V-phase voltage command value V also has a rising command value Vup and a falling command value Vdown within one carrier cycle, and the biphase modulated W-phase voltage command correction value W also has a rising command value Wup and a falling command value Wdown within one carrier cycle.

[0020] Then, by comparing the rising command value Uup and falling command value Udown of the U-phase voltage command value Cu, the rising command value Vup and falling command value Vdown of the V-phase voltage command value V, the rising command value Wup and falling command value Wdown of the W-phase voltage command value W, and the magnitude of the carrier signal, a PWM signal is generated as the drive command signal for the inverter circuit. This PWM signal is the normalized phase voltages of the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw.

[0021] like Figure 14 As shown, the lower arm switching element of phase W is fixed in the on state during the phase from 0° to 120°, while the lower arm switching element of phase U is fixed in the on state during the phase from 120° to 240°. Additionally, the lower arm switching element of phase V is fixed in the on state during the phase from 240° to 360°.

[0022] Furthermore, the neutral point potential Vc of the motor is also calculated using the average value of each phase voltage (Vu+Vv+Vw) / 3, but in the method of Patent Document 2, as... Figure 15 As shown, by utilizing the voltage command values ​​U, V, and W of two-phase modulation, the switching frequency of the upper and lower arm switching elements in each phase is reduced to 2 / 3. Therefore, the common-mode noise generated by the fluctuation of the neutral point potential Vc is also reduced to 2 / 3 compared to the general three-phase modulation method. Furthermore, the fluctuation range of the neutral point potential Vc is 4 (-3 to 1). Figure 15 yes Figure 14 An enlarged view of section Z2. Additionally, the conditions at this time are a carrier frequency of 20kHz and a DC voltage of 350V.

[0023] Figure 16 The spectrum of the neutral point potential in the inverter device using the two-phase modulation scheme is shown. This figure clearly demonstrates that, based on the two-phase modulation scheme, while maintaining a high modulation rate, it differs from typical three-phase modulation (…). Figure 13 Compared to the previous method, the change in neutral point potential Vc was suppressed.

[0024] The present invention was made in view of the existing situation and its object is to provide an inverter device based on a two-phase modulation method that can further reduce common-mode noise.

[0025] Technical means for solving technical problems

[0026] The inverter device of the first invention includes: an inverter circuit that connects upper arm switching elements and lower arm switching elements in series between upper arm power lines and lower arm power lines in each phase, and applies the phase voltage of the connection points of the upper and lower arm switching elements in each phase as a three-phase AC output to the motor; and a control device that controls the switching of the upper and lower arm switching elements in each phase of the inverter circuit. The inverter device is characterized in that the control device has: a phase voltage command calculation unit that calculates and outputs three-phase modulated voltage command values ​​for generating the voltages applied to each phase of the motor; and an inter-line modulation calculation unit. The line-to-line modulation calculation unit calculates a two-phase modulation voltage command value based on the three-phase modulation voltage command value. This two-phase modulation voltage command value fixes the on / off state of the upper and lower arm switching elements of one phase of the inverter circuit and modulates the on / off state of the upper and lower arm switching elements of the other two phases. The PWM signal generation unit generates a PWM signal for PWM control of the inverter circuit based on the two-phase modulation voltage command value. The control device synchronizes the switching timing of the upper and lower arm switching elements of the two phases whose on / off states are modulated, and uses changes in the voltage of other phases to offset changes in the phase voltage applied to the motor.

[0027] The inverter device of the second invention is characterized in that, in the above invention, the control device starts switching within a predetermined range from a state in which the upper arm switching element of one of the two phases, which is modulated by the on / off state, is turned on and the lower arm switching element of the other is turned on.

[0028] The inverter device of the third invention is characterized in that, in the above inventions, the control device synchronizes only one of the timing of the decrease of the phase voltage of one of the two phases whose on / off states are modulated and the timing of the increase of the phase voltage of the other, and the timing of the increase of the phase voltage of one phase and the timing of the decrease of the phase voltage of the other.

[0029] The inverter device of the fourth invention is characterized in that, in the above invention, the control device selects and synchronizes the timing of the switch with the larger surge voltage.

[0030] The inverter device of the fifth invention is characterized in that, in the above inventions, the control device modulates the on / off state of the upper and lower arm switching elements of a specific phase, and fixes the on / off state of the upper and lower arm switching elements of one of the remaining two phases.

[0031] The inverter device of the sixth invention is characterized in that, in the above invention, the upper and lower arm switching elements of a specific phase are configured to exchange heat with the lowest temperature part of the electric compressor.

[0032] The inverter device of the seventh invention is characterized in that, in the above inventions, the inter-line modulation calculation unit outputs a two-phase modulation voltage command value, which causes the on / off state of the upper and lower arm switching elements of a specific phase to be always modulated, and the on / off state of the upper and lower arm switching elements of one of the remaining two phases is fixed, and the PWM signal generation unit corrects the two-phase modulation voltage command value output by the inter-line modulation calculation unit, thereby using the change in the phase voltage of other phases to offset the change in the phase voltage applied to the motor.

[0033] Invention Effects

[0034] According to the present invention, an inverter device is provided, comprising: an inverter circuit that connects upper arm switching elements and lower arm switching elements in series between upper arm power lines and lower arm power lines in each phase, and applies the phase voltages at the connection points of the upper and lower arm switching elements in each phase as a three-phase AC output to a motor; and a control device that controls the switching of the upper and lower arm switching elements in each phase of the inverter circuit. In the inverter device, the control device includes: a phase voltage command calculation unit that calculates and outputs three-phase modulated voltage command values ​​for generating the voltages applied to each phase of the motor; and inter-line modulation... The inverter circuit includes a modulation calculation unit that calculates a two-phase modulation voltage command value based on the three-phase modulation voltage command value. This two-phase modulation voltage command value fixes the on / off state of the upper and lower arm switching elements of one phase of the inverter circuit and modulates the on / off state of the upper and lower arm switching elements of the other two phases. It also includes a PWM signal generation unit that generates a PWM signal for PWM control of the inverter circuit based on the two-phase modulation voltage command value. Therefore, by using two-phase modulation, the number of switching operations of the upper and lower arm switching elements can be reduced, switching losses and heat generation can be reduced, and the fluctuation of the neutral point potential of the motor can also be reduced.

[0035] In addition, the control device synchronizes the switching timing of the upper and lower arm switching elements of the two phases whose on / off states are modulated, and uses the changes in other phase voltages to offset the changes in the phase voltage applied to the motor. Therefore, the switching timing of the switching elements further suppresses the fluctuations in the neutral point potential of the motor, thereby significantly suppressing the generation of common-mode noise.

[0036] Furthermore, even in the event of errors in the synchronization of the switching timing, the noise suppression effect brought about by reducing the fluctuation of the neutral point potential through the above two-phase modulation can be enjoyed to a minimum, thus enabling a relatively stable inverter device with low noise overall.

[0037] In this case, if a control device such as the second invention starts a predetermined interval of switching from a state in which the upper arm switching element of one of the two phases modulated by the on / off state is turned on and the lower arm switching element of the other is turned on, then the changes in the phase voltage can be smoothly offset by the changes in the other phase voltages.

[0038] In particular, if a control device such as the third invention synchronizes only one of the timing of the decrease of the phase voltage of one of the two phases modulated by the on / off state and the timing of the increase of the phase voltage of the other, and the timing of the increase of the phase voltage of one phase and the decrease of the phase voltage of the other, the adverse situation of narrowing of the modulation amplitude can be eliminated or suppressed, thereby enabling the motor to be driven with a high modulation rate.

[0039] In this case, if a control device such as the fourth invention selects a switch with a large surge voltage and synchronizes it, the surge voltage generated in the circuit can be effectively suppressed.

[0040] Furthermore, if a control device such as the fifth invention keeps the on / off state of the upper and lower arm switching elements of a specific phase modulated and fixes the on / off state of the upper and lower arm switching elements of one of the remaining two phases, then two-phase modulation and switching timing synchronization can be easily and smoothly achieved.

[0041] In this case, by configuring the upper and lower arm switching elements of a specific phase to exchange heat with the lowest-temperature part of the electric compressor, as in the sixth invention, the upper and lower arm switching elements of the specific phase that are always switching on and off without a fixed on / off state that would cause the temperature to rise can be effectively cooled, thus preventing adverse situations such as the electric compressor being forced to stop.

[0042] Furthermore, if, as in the seventh invention, the inter-line modulation calculation unit outputs a two-phase modulation voltage command value, which modulates the on / off state of the upper and lower arm switching elements of a specific phase to be constantly modulated, and fixes the on / off state of the upper and lower arm switching elements of one of the remaining two phases, and the PWM signal generation unit corrects the two-phase modulation voltage command value output by the inter-line modulation calculation unit, thereby using the changes in other phase voltages to offset the changes in the phase voltage applied to the motor, then the inter-line modulation calculation unit does not need to output a two-phase modulation voltage command value that uses the changes in other phase voltages to offset the changes in phase voltage, thereby simplifying the calculation. Attached Figure Description

[0043] Figure 1 This is a circuit diagram of an inverter device according to an embodiment of the present invention.

[0044] Figure 2 It has Figure 1A longitudinal sectional side view of an electric compressor according to an embodiment of an inverter device.

[0045] Figure 3 Viewed from the inverter housing side Figure 2 The side view of the electric compressor without the cover and base plate is shown.

[0046] Figure 4 It is shown Figure 1 A graph showing the two-phase modulated voltage command correction value of the inverter device versus the carrier signal, phase voltage, and neutral point potential of the motor.

[0047] Figure 5 yes Figure 4 An enlarged view of the Z3 section of the frame.

[0048] Figure 6 yes Figure 4 An enlarged view of the Z4 section of the frame.

[0049] Figure 7 yes Figure 4 An enlarged view of the Z5 section of the frame.

[0050] Figure 8 yes Figure 4 An enlarged view of section Z6 of the frame.

[0051] Figure 9 It is shown Figure 1 A graph showing the spectrum of the neutral point potential in an inverter device.

[0052] Figure 10 This is a graph showing the voltage command correction value of the three-phase modulation of an inverter device with conventional three-phase modulation matching the switching timing, relative to the carrier signal, phase voltage, and neutral point potential of the motor.

[0053] Figure 11 yes Figure 10 An enlarged view of the Z1 section of the frame.

[0054] Figure 12 It is shown Figure 10 A graph showing the spectrum of the neutral point potential in an inverter device.

[0055] Figure 13 This is a graph showing the spectrum of the neutral point potential in a typical three-phase modulation inverter device.

[0056] Figure 14 This is a diagram showing the voltage command value of a conventional two-phase modulation inverter device relative to the carrier signal, phase voltage, and neutral point potential of the motor.

[0057] Figure 15 yes Figure 14 An enlarged view of the Z2 section of the frame.

[0058] Figure 16 It is shown Figure 14 A graph showing the spectrum of the neutral point potential in an inverter device. Detailed Implementation

[0059] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, refer to... Figure 2 and Figure 3 The electric compressor (so-called inverter-integrated electric compressor) 16 of an embodiment integrated with the inverter device 1 of the present invention is described. Furthermore, the electric compressor 16 of this embodiment forms part of the refrigerant circuit of a vehicle air conditioning system installed in vehicles such as engine-driven automobiles, hybrid automobiles, or electric vehicles.

[0060] (1) Structure of electric compressor 16

[0061] exist Figure 2 In this case, the metallic cylindrical housing 2 of the electric compressor 16 is divided into a compression mechanism housing 4 and an inverter housing 6 by a partition wall 3 intersecting the axial direction of the housing 2. The compression mechanism housing 4 houses, for example, a scroll compressor 7 and an electric motor 8 that drives the compressor 7. In this case, the electric motor 8 is an IPMSM (Interior Permanent Magnet Synchronous Motor), which consists of a stator 9 fixed to the housing 2 and a rotor 11 rotating inside the stator 9.

[0062] A bearing portion 12 is formed at the center of the compression mechanism housing portion 4 on the partition wall 3. One end of the drive shaft 13 of the rotor 11 is supported by the bearing portion 12, and the other end of the drive shaft 13 is connected to the compression mechanism 7. An intake port 14 is formed near the partition wall 3 at a position corresponding to the compression mechanism housing portion 4 of the housing 2. When the rotor 11 (drive shaft 13) of the motor 8 rotates to drive the compression mechanism 7, the cryogenic refrigerant, which is the working fluid, flows into the compression mechanism housing portion 4 of the housing 2 from the intake port 14 and is attracted and compressed by the compression mechanism 7.

[0063] Then, the refrigerant, compressed by the compression mechanism 7 to a high temperature and high pressure, is discharged from the outlet (not shown) to the outside of the housing 2 in the aforementioned refrigerant circuit. Furthermore, since the low-temperature refrigerant flowing in from the suction port 14 passes near the partition wall 3 and around the motor 8, and is attracted by the compression mechanism 7, the partition wall 3 is also cooled.

[0064] The inverter device 1 of the present invention, which is used to drive and control the motor 8, is housed in the inverter housing 6, which is separated from the compression mechanism housing 4 by the partition wall 3. In this case, the inverter device 1 supplies power to the motor 8 through sealed terminals and leads that pass through the partition wall 3.

[0065] (2) Structure of inverter device 1 (configuration of switching elements 18A to 18F)

[0066] In this embodiment, the inverter device 1 comprises a substrate 17, six switching elements (upper arm switching elements 18A, 18B, 18C and lower arm switching elements 18D, 18E, 18F) wired on one surface of the substrate 17, a control device 21 wired on the other surface of the substrate 17, and HV connectors, LV connectors (not shown in the figure). In this embodiment, each of the upper and lower arm switching elements 18A to 18F is constructed from an insulated-gate bipolar transistor (IGBT) obtained by assembling a MOS structure into the gate portion.

[0067] In this case, in the embodiment, the upper arm switching element 18A and lower arm switching element 18D of the U-phase half-bridge circuit 19U, the upper arm switching element 18B and lower arm switching element 18E of the V-phase half-bridge circuit 19V, and the upper arm switching element 18C and lower arm switching element 18F of the W-phase half-bridge circuit 19W are arranged in pairs, as follows: Figure 3 As shown, the upper and lower arm switching elements 18A and 18D, upper and lower arm switching elements 18B and 18E, and upper and lower arm switching elements 18C and 18F arranged in a group are radially arranged around the center of the substrate 17.

[0068] Additionally, in this embodiment, the upper and lower arm switching elements 18A and 18D of the U-phase half-bridge circuit 19U are located on the suction port 14 side, while the upper and lower arm switching elements 18B and 18E of the V-phase half-bridge circuit 19V are arranged on... Figure 3 After rotating 90° counterclockwise, the upper and lower arm switching elements 18C and 18F of the W-phase half-bridge circuit 19W are positioned on opposite sides of the intake port 14. Then, as... Figure 3 As shown by the dashed arrow, the refrigerant drawn in from the suction port 14 rotates counterclockwise around the axis of the housing 2. Therefore, the upper and lower arm switching elements 18A and 18D of the U-phase half-bridge circuit 19U are located on the upstream side relative to the flow of the drawn refrigerant (the lowest temperature position in the electric compressor 16), the upper and lower arm switching elements 18B and 18E of the V-phase half-bridge circuit 19V are located on its downstream side, and the switching elements 18C and 18F of the W-phase half-bridge circuit 19W are arranged on the downstream side.

[0069] Furthermore, the terminal portions 22 of each switching element 18A to 18F are connected to the substrate 17 with the terminal portion 22 positioned at the center of the substrate 17. The inverter device 1 assembled in this manner is housed within the inverter housing 6 with the surface of each switching element 18A to 18F positioned on the spacer wall 3, mounted on the spacer wall 3, and sealed by the cover 23. In this case, the substrate 17 is fixed to the spacer wall 3 by a protrusion 24 extending from the spacer wall 3.

[0070] Therefore, with the inverter unit 1 mounted on the partition wall 3, each switching element 18A to 18F is in close contact with the partition wall 3 directly or through a specified insulating and heat-conducting material, thereby forming a heat exchange relationship with the partition wall 3 of the housing 2. At this time, each switching element 18A to 18F is arranged in a manner that avoids the positions corresponding to the bearing portion 12 and the drive shaft 13, and is arranged around them. Figure 3 ).

[0071] As described above, since the partition wall 3 is cooled by the refrigerant drawn into the compressor housing 4, each switching element 18A to 18F forms a heat exchange relationship with the drawn refrigerant through the partition wall 3. The refrigerant drawn into the compressor housing 4 is cooled by the thickness of the partition wall 3, and each switching element 18A to 18F dissipates heat to the refrigerant through the partition wall 3.

[0072] (3) Circuit structure of inverter device 1

[0073] then, Figure 1 In this embodiment, the inverter device 1 includes the aforementioned three-phase inverter circuit 28 and control device 21. The inverter circuit 28 is a circuit that converts the DC voltage of the DC power supply (vehicle battery: for example, 350V) 29 into a three-phase AC voltage (three-phase AC output) and applies it to the motor 8. This 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. Each phase half-bridge circuit 19U to 19W independently has upper arm switching elements 18A to 18C and lower arm switching elements 18D to 18F. Furthermore, each switching element 18A to 18F is connected in reverse parallel with a freewheeling diode 31.

[0074] The upper ends of the upper arm switching elements 18A to 18C of the inverter circuit 28 are 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 ends of the lower arm switching elements 18D to 18F of the inverter circuit 28 are connected to the lower arm power supply line (negative side bus) 15 of the DC power supply 29 and the filter capacitor 32.

[0075] 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.

[0076] The connection point (U-phase voltage Vu) 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 armature coil 41 of the U-phase of the motor 8. The connection point (V-phase voltage Vv) between the upper arm switching element 18B and the lower arm switching element 18E of the V-phase half-bridge circuit 19V is connected to the armature coil 42 of the V-phase of the motor 8. The connection point (W-phase voltage Vw) between the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half-bridge circuit 19W is connected to the armature coil 43 of the W-phase of the motor 8.

[0077] (4) Structure of control device 21

[0078] Next, the control device 21 is composed of a microprocessor with a processor. In this embodiment, a speed command value is input from the vehicle ECU, and a motor current (phase current) is input from the motor 8. 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.

[0079] The control device 21 of the embodiment includes a phase voltage command calculation unit 33, an inter-line modulation calculation unit 34, a PWM signal generation unit 36, a gate driver 37, and current sensors 26A and 26B. The current sensors 26A and 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. Each current sensor 26A and 26B is connected to the phase voltage command calculation unit 33.

[0080] In addition, current sensor 26A measures the U-phase current iu, and current sensor 26B measures the V-phase current iv. The W-phase current iw is calculated based on the aforementioned U-phase current iu and V-phase current iv. Furthermore, regarding the method for detecting the motor current of each phase, besides measuring it using current sensors 26A and 26B as in the embodiment, there are also methods such as detecting the current value of the lower arm power line 15 and estimating it using the phase voltage command calculation unit 33 based on that current value and the operating state of the motor 8. Therefore, there are no particular limitations on the method for detecting and estimating the current of each phase.

[0081] The phase voltage command calculation unit 33 calculates and generates three-phase modulation voltage command values ​​Vu' (hereinafter, U-phase voltage command value Vu'), Vv' (hereinafter, V-phase voltage command value Vv'), and Vw' (hereinafter, W-phase voltage command value Vw'). These three-phase modulation voltage command values ​​are used to generate the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw applied to the armature coils 41-43 of each phase of the motor 8 by vector control based on the electrical angle, current command value, and phase current of the motor 8. These three-phase modulation voltage command values ​​Vu', Vv', and Vw' are the voltage command values ​​when performing three-phase modulation control of the motor 8.

[0082] The inter-line modulation calculation unit 34 calculates the two-phase modulation voltage command values ​​U (U-phase voltage command value), V (V-phase voltage command value), and W (W-phase voltage command value) based on the three-phase modulation voltage command values ​​Vu', Vv', and Vw' calculated by the phase voltage command calculation unit 33. The operation of the inter-line modulation calculation unit 34 will be described later.

[0083] The PWM signal generation unit 36 ​​inputs the two-phase modulation voltage command values ​​U, V, and W calculated by the inter-line modulation calculation unit 34. After correcting these two-phase modulation voltage command values ​​U, V, and W as described later, it generates and outputs PWM signals as drive command signals 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 by comparing them with the magnitude of the carrier signal.

[0084] The gate driver 37 generates the gate voltages of the switching elements 18A and 18D of the U-phase half-bridge circuit 19U, the gate voltages of the switching elements 18B and 18E of the V-phase half-bridge circuit 19V, and the gate voltages of the switching elements 18C and 18F of the W-phase half-bridge circuit 19W based on the PWM signal output from the PWM signal generation unit 36.

[0085] Then, the switching elements 18A to 18F of the inverter circuit 28 are turned on / off based on the gate voltage output from the gate driver 37. That is, if the gate voltage is in the on state (a specified voltage value), the switching element turns on; if the gate voltage is in the off state (zero), the switching element turns off. In the case where the switching elements 18A to 18F are the aforementioned IGBTs, the gate driver 37 is a circuit for applying the gate voltage to the IGBT based on a PWM signal, and is composed of an optocoupler, a logic IC, a transistor, etc.

[0086] The voltage at the connection point of 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 to the armature coil 41 of the U-phase of the motor 8. The voltage at the connection point of 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 to the armature coil 42 of the V-phase of the motor 8. The voltage at the connection point of 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 to the armature coil 43 of the W-phase of the motor 8.

[0087] (5) Operation of control device 21

[0088] Next, refer to Figures 4-9 To explain the operation of control device 21.

[0089] (5-1) Operation of the line modulation calculation unit 34

[0090] In the embodiment, the inter-line modulation calculation unit 34 of the control device 21 always modulates the on / off state of the upper and lower arm switching elements 18A and 18D of a specific phase, in the embodiment U phase. For the remaining two phases, namely V phase and W phase, it compares the three-phase modulation voltage command values ​​calculated by the phase voltage command calculation unit 33, namely the V phase voltage command value Vv' and the W phase voltage command value Vw', calculates and outputs the two-phase modulation voltage command values ​​that fix the on / off state of the switching elements 18B, 18E, 18C, and 18F of the phase with the largest absolute value to the on or off state, namely the U phase voltage command value U, the V phase voltage command value V, and the W phase voltage command value W. Thus, compared with the case of performing three-phase modulation control, it performs two-phase modulation control that reduces the number of switching elements 18A to 18F.

[0091] In the two-phase modulation control involved, the switching frequency of each phase switching element 18A to 18F is reduced to 2 / 3. Therefore, compared with three-phase modulation control, the switching losses and resulting heat generation in each switching element 18A to 18F are suppressed. In addition, due to the reduction in the number of switching, the fluctuation of the neutral point potential Vc can also be reliably suppressed to 2 / 3 by two-phase modulation control.

[0092] (5-2) Operation of PWM signal generation unit 36

[0093] Next, the operation of the PWM signal generation unit 36 ​​of the control device 21 in the embodiment will be explained. Figure 4This is a graph representing the two-phase modulated voltage command correction values ​​obtained after correcting the two-phase modulated voltage command values ​​of inverter device 1, namely U-phase voltage command value U, V-phase voltage command value V, and W-phase voltage command value W, as well as the carrier signal, phase voltages Vu, Vv, Vw, and the neutral point potential Vc of motor 8. Figure 5 yes Figure 4 An enlarged view of the Z3 section of the frame. Figure 6 yes Figure 4 An enlarged view of the Z4 section of the frame. Figure 7 yes Figure 4 An enlarged view of the Z5 section of the frame. Figure 8 yes Figure 4 An enlarged view of section Z6 of the frame.

[0094] Furthermore, each value in each graph is a value normalized (corrected to -1 to 1) to the DC voltage Vdc. Additionally, the conditions at this time are a carrier frequency of 20kHz and a DC voltage of 350V. Figure 4 In the circuit, the lower arm switch element 18F of phase W is fixed in the conducting state during the phase from 0° to 120°, the upper arm switch element 18B of phase V is fixed in the conducting state during the phase from 120° to 180°, the upper arm switch element 18C of phase W is fixed in the conducting state during the phase from 180° to 240°, and the lower arm switch element 18E of phase V is fixed in the conducting state during the phase from 240° to 360°.

[0095] In this embodiment, the PWM signal generation unit 36 ​​corrects the two-phase modulation voltage command values ​​output by the inter-line modulation calculation unit 34, namely the U-phase voltage command value U, the V-phase voltage command value V, and the W-phase voltage command value W, to obtain the two-phase modulation U-phase voltage command correction value Cu, the V-phase voltage command correction value Cv, and the W-phase voltage command correction value Cw. It then performs control to synchronize the switching timing of the upper and lower arm switching elements 18A to 18F of each phase, and uses the changes in other phase voltages to offset the changes in the phase voltages Vu, Vv, and Vw applied to the motor 8, thereby suppressing the fluctuation of the neutral point potential Vc.

[0096] The operation of the PWM signal generation unit 36 ​​will be explained in detail below with reference to the figures. In this case, a sawtooth wave carrier signal (solid line) is also used. Therefore, the U-phase voltage command correction value Cu has a rising command value Cuup (thin dashed line, the same below) and a falling command value Cudown (wide dashed line, the same below) within one carrier cycle. Similarly, the V-phase voltage command correction value Cv also has a rising command value Cvup and a falling command value Cvdown within one carrier cycle, and the W-phase voltage command correction value Cw also has a rising command value Cwup and a falling command value Cwdown within one carrier cycle.

[0097] Then, by comparing the rising command value Cuup and falling command value Cudown of the U-phase voltage command correction value Cu, the rising command value Cvup and falling command value Cvdown of the V-phase voltage command correction value Cv, the rising command value Cwup and falling command value Cwdown of the W-phase voltage command correction value Cw, and the magnitude of the carrier signal, a PWM signal is generated as the drive command signal for the inverter circuit 28. This PWM signal is the normalized phase voltages of the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw.

[0098] exist Figure 4 In the phase of the Z3 portion of the frame, such as Figure 5 As shown in the enlarged view, the inter-line modulation calculation unit 34 starts the predetermined switching period from a state where the upper arm switching element 18A of the U phase, which is always modulated in the on / off state, is turned on, and the lower arm switching elements 18E and 18F of the remaining V and W phases are turned on. In addition, the upper arm switching element 18C of the W phase is fixed to the off state, and the lower arm switching element 18F is fixed to the on state.

[0099] In this state, the PWM signal generation unit 36 ​​generates a V-phase voltage command correction value Cv, so that in Figure 5 In the example, the timing of the drop in phase U voltage Vu is synchronized with the timing of the rise in phase V voltage Vv (see [reference]). Figure 5 Phase t1 is near 44° and phase t2 is near 51°. Therefore, the variation of the neutral point potential Vc in each phase t1 and t2 is eliminated. In addition, the variation amplitude of the neutral point potential Vc is 2 of -3 to -1. Figure 4 , Figure 5 ).

[0100] However, the timing of the rise of phase U voltage Vu is not synchronized with the timing of the fall of phase V voltage Vv (see [link]). Figure 5 (The phases around 49.5° and 57°). Additionally, the timing of the U-phase voltage Vu decreasing and the timing of the V-phase voltage Vv increasing can be desynchronized, while the timing of the U-phase voltage Vu increasing and the timing of the V-phase voltage Vv decreasing can be synchronized.

[0101] That is, the PWM signal generation unit 36 ​​synchronizes only one of the timings: the timing of the U-phase voltage Vu decreasing and the timing of the V-phase voltage Vv increasing, or the timing of the U-phase voltage Vu increasing and the timing of the V-phase voltage Vv decreasing. In this case, regarding whether to synchronize the timing of the U-phase voltage Vu decreasing with the timing of the V-phase voltage Vv increasing, or to synchronize the timing of the U-phase voltage Vu increasing with the timing of the V-phase voltage Vv decreasing, the PWM signal generation unit 36 ​​selects the timing with the larger surge voltage during switching and synchronizes them. The surge voltage is calculated based on the motor current (U-phase current iu, V-phase current iv, W-phase current iw) obtained from the detection values ​​of current sensors 26A and 26B and the parasitic inductance of the circuit.

[0102] Next, in Figure 4 In the phase of the Z4 portion of the frame, such as Figure 6 As shown in the enlarged view, the inter-line modulation calculation unit 34 starts a predetermined switching period from a state where the upper arm switching element 18A of phase U, which is always modulated in the on / off state, is turned on, and the upper arm switching element 18B of phase V and the lower arm switching element 18F of phase W are turned on. In addition, the upper arm switching element 18B of phase V is fixed to be turned on, and the lower arm switching element 18E is fixed to be turned off.

[0103] In this state, the PWM signal generation unit 36 ​​generates a W-phase voltage command correction value Cw, so that in Figure 6 In the example, the timing of the drop in phase U voltage Vu is synchronized with the timing of the rise in phase W voltage Vw (see [reference]). Figure 6 Phase t3 is near 144.5° and phase t4 is near 152°. Therefore, the variation of the neutral point potential Vc at each phase t3 and t4 is eliminated. In addition, the variation amplitude of the neutral point potential Vc is 2 of 1 to 3. Figure 4 , Figure 6 ).

[0104] However, in this case, the timing of the rise of the U-phase voltage Vu is not synchronized with the timing of the fall of the W-phase voltage Vw (see [reference]). Figure 6 (The phases around 146.5° and 153.5°). Additionally, the timing of the U-phase voltage Vu decreasing and the timing of the W-phase voltage Vw increasing can be made asynchronous, while the timing of the U-phase voltage Vu increasing and the timing of the W-phase voltage Vw decreasing can be synchronized.

[0105] That is, in this case, the PWM signal generation unit 36 ​​synchronizes only one of the timing of the U-phase voltage Vu decreasing and the timing of the W-phase voltage Vw increasing, or the timing of the U-phase voltage Vu increasing and the timing of the W-phase voltage Vw decreasing. In this case, regarding whether to synchronize the timing of the U-phase voltage Vu decreasing and the timing of the W-phase voltage Vw increasing, or the timing of the U-phase voltage Vu increasing and the timing of the W-phase voltage Vw decreasing, the PWM signal generation unit 36 ​​selects the timing with the larger surge voltage during switching and synchronizes them.

[0106] Next, in Figure 4 In the phase of the Z5 portion of the frame, such as Figure 7 As shown in the enlarged view, the inter-line modulation calculation unit 34 starts a predetermined switching period from a state where the upper arm switching element 18A of phase U, which is always modulated in the on / off state, is turned on, and the lower arm switching element 18E of phase V and the upper arm switching element 18C of phase W are turned on. In addition, the upper arm switching element 18C of phase W is fixed to be turned on, and the lower arm switching element 18F is fixed to be turned off.

[0107] In this state, the PWM signal generation unit 36 ​​generates a V-phase voltage command correction value Cv, so that in Figure 7 In the example, the timing of the drop in phase U voltage Vu is synchronized with the timing of the rise in phase V voltage Vv (see [reference]). Figure 7 Phase t5 is near 216.5° and phase t6 is near 224°. Therefore, the variation of the neutral point potential Vc at each phase t5 and t6 is eliminated. In addition, the variation amplitude of the neutral point potential Vc is 2 of 1 to 3. Figure 4 , Figure 7 ).

[0108] However, in this case, the timing of the rise of phase U voltage Vu is not synchronized with the timing of the fall of phase V voltage Vv (see [reference]). Figure 6 (The phases near 218° and 226°). Additionally, the timing of the U-phase voltage Vu decreasing and the timing of the V-phase voltage Vv increasing can be made asynchronous, while the timing of the U-phase voltage Vu increasing and the timing of the V-phase voltage Vv decreasing can be synchronized.

[0109] That is, in this case, the PWM signal generation unit 36 ​​synchronizes only one of the timing of the U-phase voltage Vu decreasing and the timing of the V-phase voltage Vv increasing, or the timing of the U-phase voltage Vu increasing and the timing of the V-phase voltage Vv decreasing. In this case, regarding whether to synchronize the timing of the U-phase voltage Vu decreasing and the timing of the V-phase voltage Vv increasing, or to synchronize the timing of the U-phase voltage Vu increasing and the timing of the V-phase voltage Vv decreasing, the PWM signal generation unit 36 ​​selects the timing with the larger surge voltage during switching and synchronizes them.

[0110] Next, in Figure 4In the phase of the Z6 portion of the frame, such as Figure 8 As shown in the enlarged view, the inter-line modulation calculation unit 34 starts the predetermined switching period from a state where the upper arm switching element 18A of the U phase, which is always modulated in the on / off state, is turned on, and the lower arm switching elements 18E and 18F of the remaining V and W phases are turned on. In addition, the upper arm switching element 18B of the V phase is fixed to the off state, and the lower arm switching element 18E is fixed to the on state.

[0111] In this state, the PWM signal generation unit 36 ​​generates a W-phase voltage command correction value Cw, so that in Figure 8 In the example, the timing of the drop in phase U voltage Vu is synchronized with the timing of the rise in phase W voltage Vw (see [reference]). Figure 8 Phase t7 near 303° and phase t8 near 310.5°. Therefore, the variation of the neutral point potential Vc at each phase t7 and t8 is eliminated. In addition, the variation amplitude of the neutral point potential Vc is 2 ( ) from -3 to -1. Figure 4 , Figure 8 ).

[0112] However, in this case, the timing of the rise of the U-phase voltage Vu is not synchronized with the timing of the fall of the W-phase voltage Vw (see...). Figure 8 (The phases slightly ahead of 309° and slightly ahead of 316°). Additionally, the timing of the U-phase voltage Vu's decrease and the timing of the W-phase voltage Vw's increase can be made asynchronous, while the timing of the U-phase voltage Vu's increase and the timing of the W-phase voltage Vw's decrease can be synchronized.

[0113] That is, in this case, the PWM signal generation unit 36 ​​synchronizes only one of the timing of the U-phase voltage Vu decreasing and the timing of the W-phase voltage Vw increasing, or the timing of the U-phase voltage Vu increasing and the timing of the W-phase voltage Vw decreasing. In this case, regarding whether to synchronize the timing of the U-phase voltage Vu decreasing and the timing of the W-phase voltage Vw increasing, or the timing of the U-phase voltage Vu increasing and the timing of the W-phase voltage Vw decreasing, the PWM signal generation unit 36 ​​also selects the timing with the larger surge voltage during switching and synchronizes it accordingly.

[0114] Therefore, the common-mode noise generated in one carrier cycle can be reduced to 1 / 3. Figure 9 The spectrum (FFT result) of the neutral point potential Vc in the inverter device 1 of the embodiment is shown. As can be clearly seen from this figure, according to the present invention, compared with... Figure 12 , Figure 13 The method shown or Figure 16 Compared to the typical two-phase modulation method shown, the fluctuation of the neutral point potential Vc is more effectively suppressed.

[0115] As described above, according to the present invention, the control device 21 includes: a phase voltage command calculation unit 33 that calculates and outputs three-phase modulation voltage command values ​​to generate voltages applied to each phase of the motor 8; an inter-line modulation calculation unit 34 that calculates two-phase modulation voltage command values ​​based on the three-phase modulation voltage command values ​​to fix the on / off state of the upper and lower arm switching elements of one phase of the inverter circuit 28, and modulates the on / off state of the upper and lower arm switching elements of the other two phases; and a PWM signal generation unit 36 ​​that generates a PWM signal for PWM control of the inverter circuit 28 based on the two-phase modulation voltage command values. Therefore, the number of switching operations of the upper and lower arm switching elements 18A to 18F can be reduced by two-phase modulation, thereby reducing switching losses and heat generation, and also reducing the fluctuation of the neutral point potential of the motor 8.

[0116] Furthermore, in this invention, the control device 21 synchronizes the switching timing of the upper and lower arm switching elements of the two phases whose on / off states are modulated, and uses the changes in the phase voltage of other phases to offset the changes in the phase voltage applied to the motor 8. Therefore, the switching timing of the switching elements 18A to 18F further suppresses the fluctuation of the neutral point potential of the motor 8, thereby significantly suppressing the generation of common-mode noise.

[0117] Furthermore, even in the event of errors in the synchronization of the switching timing, the noise suppression effect brought about by reducing the fluctuation of the neutral point potential through the above two-phase modulation can be enjoyed to a minimum, thus enabling the overall stable realization of an inverter device 1 with less noise.

[0118] In this case, the control device 21 of the embodiment starts switching within a predetermined range from a state in which the upper arm switching element of one of the two phases, which is modulated by the on / off state, is on while the lower arm switching element of the other is on. Therefore, the changes in the phase voltage can be smoothly offset by the changes in the other phase voltage.

[0119] In particular, the control device 21 of the embodiment synchronizes only one of the timing of the decrease of the phase voltage of one of the two phases in the on / off state and the timing of the increase of the phase voltage of the other, and the timing of the increase of the phase voltage of one phase and the decrease of the phase voltage of the other. Therefore, it can eliminate or suppress the adverse situation of narrowing of the modulation amplitude when the timing of the two phases is synchronized, thereby enabling the motor 8 to be driven with a high modulation rate.

[0120] In this case, the control device 21 of the embodiment selects a time when the surge voltage is large during the switching and synchronizes it, thus effectively suppressing the surge voltage generated in the circuit.

[0121] In addition, the control device 21 in the embodiment ensures that the on / off state of the upper and lower arm switching elements of a specific phase (U phase in the embodiment) is always modulated, and the on / off state of the upper and lower arm switching elements of one of the remaining two phases is fixed. Therefore, it is possible to easily and smoothly achieve both two-phase modulation and switching timing synchronization.

[0122] In this case, in the embodiment, the upper and lower arm switching elements 18A, 18D of this particular phase (U phase) are configured to exchange heat with the lowest temperature part of the electric compressor 16. Figure 3 Therefore, the upper and lower arm switching elements 18A and 18D of a specific phase (U phase) that are always switching on and off without a fixed on / off state, which would cause the temperature to rise, can be effectively cooled, thereby avoiding adverse situations such as the electric compressor 16 being forced to stop.

[0123] In addition, in this embodiment, the PWM signal generation unit 36 ​​corrects the two-phase modulation voltage command value output by the inter-line modulation calculation unit 34, thereby using the change of other phase voltage to offset the change of phase voltage applied to the motor 8. Therefore, the inter-line modulation calculation unit 34 does not need to output a two-phase modulation voltage command value that offsets the change of phase voltage with the change of other phase voltage, thereby simplifying the calculation.

[0124] In addition, in this embodiment, the upper and lower arm switching elements 18A and 18D of the U phase are always switched, but the upper and lower arm switching elements of another phase (either the V phase or the W phase) can also be used. Furthermore, in this embodiment, the invention is applied to the inverter device 1 for driving and controlling the motor 8 of the electric compressor 16, but the invention is not limited to this except for the sixth item. The invention is effective for driving and controlling the motors of various devices.

[0125] In addition, Figure 4 As described above, through two-phase modulation, the lower arm switching element 18F of phase W is fixed in the conducting state during the phase interval of 0° to 120°, the upper arm switching element 18B of phase V is fixed in the conducting state during the phase interval of 120° to 180°, the upper arm switching element 18C of phase W is fixed in the conducting state during the phase interval of 180° to 240°, and the lower arm switching element 18E of phase V is fixed in the conducting state during the phase interval of 240° to 360°. However, the upper arm switching element 18B of phase V can also be... Figure 4 The upper arm switching element 18C of phase W can be fixed in the on state during the phase of 60° to 120°, and similarly, the upper arm switching element 18C of phase W can be fixed in the on state during the phase of 240° to 300°.

[0126] Label Explanation

[0127] 1 Inverter unit

[0128] 8 Electric motors

[0129] 16 Electric compressor

[0130] 18A~18F Upper and lower arm switching elements

[0131] 19U U-phase half-bridge circuit

[0132] 19V V-phase half-bridge circuit

[0133] 19W half-bridge circuit

[0134] 21 Control device

[0135] 28 Inverter Circuit

[0136] 33-phase voltage command processing unit

[0137] 34-line modulation arithmetic unit

[0138] 36 PWM signal generation unit

[0139] 37 Gate driver.

Claims

1. An inverter device, comprising: The inverter circuit connects the upper arm switching elements and the lower arm switching elements in series between the upper arm power line and the lower arm power line according to each phase, and applies the phase voltage of the connection point of the upper and lower arm switching elements of each phase as a three-phase AC output to the motor. as well as A control device that controls the switching of the upper and lower arm switching elements of each phase of the inverter circuit, characterized in that the inverter device... The control device has: A phase voltage command calculation unit calculates and outputs three-phase modulated voltage command values ​​for generating the voltages applied to each phase of the motor. The line-to-line modulation calculation unit calculates a two-phase modulation voltage command value based on the three-phase modulation voltage command value. The two-phase modulation voltage command value fixes the on / off state of the upper and lower arm switching elements of one phase of the inverter circuit and modulates the on / off state of the upper and lower arm switching elements of the other two phases. as well as The PWM signal generation unit generates a PWM signal for PWM control of the inverter circuit based on the two-phase modulation voltage command value. The control device modulates the on / off state of the upper and lower arm switching elements of a specified phase at all times, and fixes the on / off state of the upper and lower arm switching elements of one of the remaining two phases. The switching timing of the upper and lower arm switching elements of the two phases, whose on / off states are modulated, is synchronized, and the changes in the phase voltage applied to the motor are offset by changes in the voltage of other phases.

2. An inverter device, comprising: The inverter circuit connects the upper arm switching elements and the lower arm switching elements in series between the upper arm power line and the lower arm power line according to each phase, and applies the phase voltage of the connection point of the upper and lower arm switching elements of each phase as a three-phase AC output to the motor. as well as A control device that controls the switching of the upper and lower arm switching elements of each phase of the inverter circuit, characterized in that the inverter device... The control device has: A phase voltage command calculation unit calculates and outputs three-phase modulated voltage command values ​​for generating the voltages applied to each phase of the motor. The line-to-line modulation calculation unit calculates a two-phase modulation voltage command value based on the three-phase modulation voltage command value. The two-phase modulation voltage command value fixes the on / off state of the upper and lower arm switching elements of one phase of the inverter circuit and modulates the on / off state of the upper and lower arm switching elements of the other two phases. as well as The PWM signal generation unit generates a PWM signal for PWM control of the inverter circuit based on the two-phase modulation voltage command value. The inter-line modulation calculation unit outputs the two-phase modulation voltage command value, which causes the on / off state of the upper and lower arm switching elements of a specified phase to be constantly modulated, and fixes the on / off state of the upper and lower arm switching elements of one of the remaining two phases. The PWM signal generation unit corrects the two-phase modulation voltage command value output by the inter-line modulation calculation unit, thereby synchronizing the switching timing of the upper and lower arm switching elements of the two phases whose on / off states are modulated, and using changes in other phase voltages to offset changes in the phase voltage applied to the motor.

3. The inverter device as described in claim 1 or 2, characterized in that, The control device starts switching within a specified range from a state where the upper arm switching element of one of the two phases, which is modulated by the on / off state, is on and the lower arm switching element of the other is on.

4. The inverter device as described in claim 1 or 2, characterized in that, The control device synchronizes only one of the timings of the decrease in phase voltage of one phase and the increase in phase voltage of the other phase in the two phases modulated by the on / off state.

5. The inverter device as described in claim 4, characterized in that, The control device selects the timing of the switch with the larger surge voltage and synchronizes them.

6. The inverter device as described in claim 1 or 2, characterized in that, The upper and lower arm switching elements of the specified phase are configured to exchange heat with the lowest temperature part of the electric compressor.

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