Inverter control device and motor drive device

Abstract

The purpose of the present disclosure is to provide an inverter control device and a motor drive device that are capable of simplifying software processing for generating a PWM signal while suppressing pulsation of a drive current.　In order to achieve the purpose, the present disclosure provides, as a solution, an inverter control device for controlling an inverter that converts a DC voltage into an AC voltage and outputs the AC voltage to a motor, the inverter control device comprising: a carrier wave generation unit that generates a carrier wave; and a PWM control unit that generates a PWM pulse signal for controlling the operation of the inverter by pulse-width modulating a voltage command by using the carrier wave and a plurality of types of modulation signals corresponding to the number of pulses of the PWM pulse signal, wherein the PWM control unit switches the number of pulses of the PWM pulse signal while maintaining the frequency ratio of the carrier wave and the modulation signal by setting the frequency of the carrier wave to be constant and switching the plurality of types of modulation signals in a predetermined rotation speed region of the motor.

Description

Inverter control device and motor drive device

[0001] The present disclosure relates to an inverter control device and a motor drive device.

[0002] Patent Document 1 below discloses a motor control device that suppresses large currents from flowing to the motor when switching the synchronization number. This motor control device PWM controls an inverter that drives a motor and includes a synchronization control unit that performs synchronous PWM control to synchronize the phase of a carrier wave with the phase of a voltage command value. When switching the number of carrier waves (synchronization number) in one cycle of the voltage command value from a first synchronization number to a second synchronization number, the synchronization control unit provides a third period in which the frequency of the carrier wave gradually changes to a predetermined target value between a first period in which the synchronization number is controlled to the first synchronization number and a second period in which the synchronization number is controlled to the second synchronization number.

[0003] Japanese Patent Application Publication No. 2021-112010

[0004] The motor control device described above switches the number of synchronizations by switching the frequency of the carrier wave in synchronous PWM control. That is, in this motor control device, the carrier frequency of the carrier wave (triangular wave) is switched to switch the number of pulses of the PWM signal, which is the inverter control signal (the number of pulses in one period of the voltage command value).

[0005] However, in this type of pulse number switching method in synchronous PWM control, pulsation occurs in the drive current supplied from the inverter to the motor, and additional processing (software processing) is required to suppress this pulsation. In other words, the conventional pulse number switching method in synchronous PWM control has the problem that the software processing for generating the PWM signal becomes complicated.

[0006] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide an inverter control device and a motor drive device that are capable of simplifying software processing for generating a PWM signal while suppressing pulsation in the drive current.

[0007] An inverter control device of a first aspect of the present disclosure is an inverter control device that controls an inverter that converts DC voltage into AC voltage and outputs it to a motor, and includes: a carrier wave generation unit that generates a carrier wave; multiple types of modulation signals according to the number of pulses of a PWM pulse signal; and a PWM control unit that pulse-width modulates a voltage command using the carrier wave and the modulation signal to generate a PWM pulse signal for controlling the operation of the inverter, wherein the PWM control unit keeps the frequency of the carrier wave constant in a predetermined rotation speed range of the motor, and switches between multiple types of the modulation signals to switch the number of pulses of the PWM pulse signal while maintaining the frequency ratio between the carrier wave and the modulation signal.

[0008] In a second aspect of the inverter control device of the present disclosure, in the first aspect, when the inverter is subjected to synchronous PWM control, the modulation signal is a trapezoidal wave signal or a modified trapezoidal wave signal in which a square wave is superimposed on the trapezoidal wave signal.

[0009] The inverter control device of a third aspect of the present disclosure is the first or second aspect, in which, when the inverter fundamental frequency becomes high, the modulation signal is switched to reduce the number of pulses, thereby performing synchronous PWM control of the inverter.

[0010] The inverter control device of a fourth aspect of the present disclosure is the third aspect, and reduces the number of pulses in the order of 9, 5, and 1.

[0011] A motor drive device according to a first aspect of the present disclosure includes the inverter control device according to any one of the first to fourth aspects, and an inverter controlled by the inverter control device and outputting a drive signal to a motor.

[0012] According to the present disclosure, it is possible to provide an inverter control device and a motor drive device that can simplify software processing for generating a PWM signal while suppressing pulsation in the drive current.

[0013] FIG. 1 is a block diagram showing a configuration of an inverter control device and a motor drive device according to an embodiment of the present disclosure. FIG. 2 is a block diagram showing a detailed configuration of the inverter control device according to an embodiment of the present disclosure. FIG. 3 is a characteristic diagram showing the operation of the inverter control device and the motor drive device according to an embodiment of the present disclosure. FIG. 4 is a first waveform diagram showing the operation of the inverter control device and the motor drive device according to an embodiment of the present disclosure. FIG. 5 is a fifth waveform diagram showing the operation of the inverter control device and the motor drive device according to an embodiment of the present disclosure. FIG. 6 is a sixth waveform diagram showing the operation of the inverter control device and the motor drive device according to an embodiment of the present disclosure.

[0014] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. As shown in FIG. 1 , a motor drive device A according to this embodiment includes an inverter control device B according to this embodiment and an inverter C controlled by the inverter control device B.

[0015] This motor drive device A is an electric device that outputs three-phase drive signals, i.e., a U-phase drive signal Ku, a V-phase drive signal Kv, and a W-phase drive signal Kw, to a motor D to drive and rotate the motor D. This motor drive device A is also an in-vehicle device that is mounted on an electrically powered vehicle such as an electric car or a hybrid car, and drives the motor D as a traction motor (travel power source) that generates travel power.

[0016] First, the inverter C will be described. This inverter C is, for example, a three-phase inverter, and has three switching legs corresponding to the three phases (U phase, V phase, W phase) of the motor D, namely, a U-phase switching leg, a V-phase switching leg, and a W-phase switching leg.

[0017] The U-phase switching leg is a series circuit of a U-phase upper arm switching transistor and a U-phase lower arm switching transistor. The V-phase switching leg is a series circuit of a V-phase upper arm switching transistor and a V-phase lower arm switching transistor. The W-phase switching leg is a series circuit of a W-phase upper arm switching transistor and a W-phase lower arm switching transistor.

[0018] The six switching transistors are controlled to be ON (conductive) or OFF (non-conductive) by six PWM signals input from the inverter control device B. That is, the U-phase upper arm switching transistor is controlled to be ON (conductive) or OFF (non-conductive) by a first PWM signal Gu, and the U-phase lower arm switching transistor is controlled to be ON (conductive) or OFF (non-conductive) by a second PWM signal Gx.

[0019] The V-phase upper arm switching transistor is controlled to be ON (conductive) or OFF (non-conductive) by a third PWM signal Gv, the V-phase lower arm switching transistor is controlled to be ON (conductive) or OFF (non-conductive) by a fourth PWM signal Gy, the W-phase upper arm switching transistor is controlled to be ON (conductive) or OFF (non-conductive) by a fifth PWM signal Gw, and the W-phase lower arm switching transistor is controlled to be ON (conductive) or OFF (non-conductive) by a sixth PWM signal Gz.

[0020] The inverter C generates the three-phase drive currents Ku, Kv, and Kw by converting DC power supplied from a battery pack (high-voltage power supply) (not shown) into AC power using three switching legs. That is, the inverter C generates three-phase drive signals, i.e., a U-phase drive signal Ku, a V-phase drive signal Kv, and a W-phase drive signal Kw, based on the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz, thereby driving the motor D to rotate.

[0021] The battery pack is, for example, a lithium-ion battery, and includes a plurality of battery cells electrically connected in series. Of a pair of output terminals of this battery pack, a low-potential output terminal (negative terminal) is connected to one of a pair of input terminals provided on the inverter C, and a high-potential output terminal (positive terminal) is connected to the other of the pair of input terminals provided on the inverter C.

[0022] That is, one input terminal of the inverter C is connected to the negative terminal of the battery pack, one terminal of the first contactor C, and the other input terminal is connected to the positive terminal of the battery pack. A switch such as a contactor (not shown) is provided between the inverter C and the battery pack. This switch is an electrical device that turns on and off the supply of DC power from the battery pack to the inverter C.

[0023] The inverter C also has a total of six control terminals corresponding to the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz. That is, the first control terminal is connected to a first output terminal of the inverter control device B that outputs the first PWM signal Gu, and the second control terminal is connected to a second output terminal of the inverter control device B that outputs the second PWM signal Gx.

[0024] The third control terminal is connected to a third output terminal in the inverter control device B that outputs a third PWM signal Gv, and the fourth control terminal is connected to a fourth output terminal in the inverter control device B that outputs a fourth PWM signal Gy. The fifth control terminal is connected to a fifth output terminal in the inverter control device B that outputs a fifth PWM signal Gw, and the sixth control terminal is connected to a sixth output terminal in the inverter control device B that outputs a sixth PWM signal Gz.

[0025] Furthermore, the inverter C has three output terminals corresponding to the three phases (U phase, V phase, W phase) of the motor D, namely, a U-phase output terminal, a V-phase output terminal, and a W-phase output terminal. In the inverter C, the U-phase output terminal is connected to the U-phase winding of the motor D and outputs a U-phase drive signal Ku to the motor D. The V-phase output terminal is connected to the V-phase winding of the motor D and outputs a V-phase drive signal Kv to the motor D. Furthermore, the W-phase output terminal is connected to the W-phase winding of the motor D and outputs a W-phase drive signal Kw to the motor D.

[0026] Next, the inverter control device B according to this embodiment will be described. The inverter control device B controls the target torque T ０ and inverter fundamental frequency f ０ The first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz are generated based on the above.

[0027] That is, the inverter control device B has two input terminals connected to the upper control device in addition to the first to sixth output terminals described above. One of the two input terminals is connected to the upper control device via a target torque T ０ The other input terminal is connected to a first output terminal that outputs an inverter fundamental frequency f ０ is connected to a second output terminal that outputs

[0028] This inverter control device B controls the target torque T ０ and inverter fundamental frequency f ０ In other words, the inverter control device B according to this embodiment is configured as a software control device including a CPU (Central Processing Unit), semiconductor memories such as ROM (Read Only Memory) and RAM (Random Access Memory), input / output circuits, etc.

[0029] Such an inverter control device B has the functional components shown in Fig. 2. Each of these functional components is realized by the cooperation of hardware and software resources in the inverter control device B, and each has a predetermined number of input terminals and output terminals.

[0030] That is, the inverter control device B according to this embodiment includes a command value generator 1, a first modulation signal generator 2, a second modulation signal generator 3, a modulation signal switcher 4, a carrier wave generator 5, and a PWM signal generator 6.

[0031] The command value generator 1 calculates the target torque T ０ and inverter fundamental frequency f ０ One of the input terminals of this command value generator 1 is one of the input terminals of the inverter control device B described above, and is connected to a first output terminal of the upper control device, and receives the target torque T ０ The other input terminal of this command value generator 1 is the other input terminal of the inverter control device B described above, and is connected to the second output terminal of the upper control device, and receives the inverter fundamental frequency f ０ Accept.

[0032] Such a command value generator 1 calculates the target torque T ０ and inverter fundamental frequency f ０ Based on this, five command values, namely, a modulation signal frequency command f, a modulation factor M, a square wave superposition rate γ, a frequency domain command Z, and a carrier wave command fc, are generated, and the five command values ​​are output from five output terminals, respectively.

[0033] Of the five output terminals of this command value generator 1, the first output terminal is connected to the first input terminal of the first modulation signal generator 2 and the first input terminal of the second modulation signal generator 3, and outputs the modulation signal frequency command f to the first modulation signal generator 2 and the second modulation signal generator 3.

[0034] A second output terminal of the command value generator 1 is connected to a second input terminal of the first modulation signal generator 2 and a second input terminal of the second modulation signal generator 3, and outputs the modulation factor M to the first modulation signal generator 2 and the second modulation signal generator 3. A third output terminal of the command value generator 1 is connected to a third input terminal of the second modulation signal generator 3, and outputs the square wave superposition factor γ to the second modulation signal generator 3.

[0035] A fourth output terminal of the command value generator 1 is connected to the control terminal of the modulation signal switch 4, and outputs the frequency domain command Z to the modulation signal switch 4. A fifth output terminal of the command value generator 1 is connected to the input terminal of the carrier wave generator 5, and outputs the carrier wave command fc to the carrier wave generator 5.

[0036] Here, the target torque T ０ (torque generated by motor C) and inverter fundamental frequency f ０ For example, there is a relationship between the maximum torque at each frequency as shown in Figure 3. This relationship is set to suppress the operating loss of inverter C, i.e., the switching loss of the six switching transistors that make up inverter C, during PWM control of inverter C. Note that, for example, if the torque command from the higher-level source is very small, the torque may remain constant across the entire range. Even in this case, the system may change from asynchronous to synchronous depending on the frequency, reducing the number of pulses.

[0037] As shown in FIG. 3, the inverter fundamental frequency f ０ is the target torque T ０ In the region where the inverter fundamental frequency f is relatively large, the inverter fundamental frequency f is set relatively low. ０ is set relatively high in a region where the target torque T0 is relatively small.

[0038] Also, as shown in FIG. 3, the target torque T ０ is relatively large, and the inverter fundamental frequency f ０ The regions 1 and 2 where the target torque T ０ is relatively small, and the inverter fundamental frequency f０ Regions 3, 4, 5 and 6 where the voltage Vcc is relatively high are operating regions in which the inverter control device B controls the inverter C in synchronous PWM mode.

[0039] The first modulation signal generator 2 generates three modulation signals to be used in regions 1, 2, and 3, based on the modulation signal frequency command f and modulation factor M input from the command value generator 1. That is, the first modulation signal generator 2 generates a U-phase element modulation signal Su1, a V-phase element modulation signal Sv1, and a W-phase element modulation signal Sw1 corresponding to the three operating regions, i.e., regions 1, 2, and 3.

[0040] The U-phase element modulation signal Su1, V-phase element modulation signal Sv1, and W-phase element modulation signal Sw1, which correspond to regions 1 and 2, are two-phase modulation signals for asynchronous PWM control, as shown in Figure 4A. In contrast, the U-phase element modulation signal Su1, V-phase element modulation signal Sv1, and W-phase element modulation signal Sw1, which correspond to region 3, are two-phase modulation signals for synchronous PWM control, as shown in Figure 4B. Such two-phase modulation signals for asynchronous PWM control and two-phase modulation signals for synchronous PWM control are commonly used in PWM control.

[0041] The first modulation signal generator 2 has three output terminals in addition to the first and second input terminals described above. Of the three output terminals of the first modulation signal generator 2, the first output terminal is connected to the first input terminal of the modulation signal switch 4 and outputs a U-phase element modulation signal Su1 to the modulation signal switch 4. The second output terminal of the first modulation signal generator 2 is connected to the second input terminal of the modulation signal switch 4 and outputs a V-phase element modulation signal Sv1 to the modulation signal switch 4. Furthermore, the third output terminal of the first modulation signal generator 2 is connected to the third input terminal of the modulation signal switch 4 and outputs a W-phase element modulation signal Sw1 to the modulation signal switch 4.

[0042] The second modulation signal generator 3 generates three modulation signals to be used in regions 4, 5, and 6, based on the modulation signal frequency command f, modulation factor M, and square wave superposition factor γ input from the command value generator 1. That is, the second modulation signal generator 3 generates a U-phase element modulation signal Su2, a V-phase element modulation signal Sv2, and a W-phase element modulation signal Sw2 corresponding to the three operating regions, i.e., regions 4, 5, and 6.

[0043] The U-phase element modulation signal Su2, V-phase element modulation signal Sv2, and W-phase element modulation signal Sw2 corresponding to region 4 are trapezoidal wave modulation signals for synchronous PWM control, as shown in Fig. 4C. As will be described in detail later, this trapezoidal wave modulation signal sets the number of pulses of the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz in one cycle to 9 pulses (9 pulses).

[0044] In contrast, U-phase element modulation signal Su2, V-phase element modulation signal Sv2, and W-phase element modulation signal Sw2, which correspond to region 5, are modified trapezoidal wave modulation signals for synchronous PWM control, as shown in Fig. 4D. As will be described in detail later, this modified trapezoidal wave modulation signal sets the number of pulses of the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz in one cycle to five pulses (five pulses).

[0045] 4E, the U-phase element modulation signal Su2, V-phase element modulation signal Sv2, and W-phase element modulation signal Sw2 corresponding to region 6 are trapezoidal wave modulation signals for synchronous PWM control. As will be described in detail later, these trapezoidal wave modulation signals set the number of pulses of the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz in one cycle to one pulse (one pulse).

[0046] The second modulation signal generator 3 has three output terminals in addition to the first and second input terminals described above. Of the three output terminals of the second modulation signal generator 3, the first output terminal is connected to the fourth input terminal of the modulation signal switcher 4 and outputs the U-phase element modulation signal Su2 to the modulation signal switcher 4. The second output terminal of the second modulation signal generator 3 is connected to the fifth input terminal of the modulation signal switcher 4 and outputs the V-phase element modulation signal Sv2 to the modulation signal switcher 4. The third output terminal of the second modulation signal generator 3 is connected to the sixth input terminal of the modulation signal switcher 4 and outputs the W-phase element modulation signal Sw2 to the modulation signal switcher 4.

[0047] The modulation signal switch 4 is a multiplexer that selects a modulation signal based on the frequency domain command Z. That is, this modulation signal switch 4 alternatively selects one of a plurality of element modulation signals, namely, U-phase element modulation signal Su1, V-phase element modulation signal Sv1, and W-phase element modulation signal Sw1 generated by the first modulation signal generator 2, and U-phase element modulation signal Su2, V-phase element modulation signal Sv2, and W-phase element modulation signal Sw2 generated by the second modulation signal generator 3, and outputs it as the U-phase modulation signal Su, the V-phase modulation signal Sv, and the W-phase modulation signal Sw.

[0048] The modulation signal switch 4 has three output terminals in addition to the first to sixth input terminals described above. Of the three output terminals of the modulation signal switch 4, the first output terminal is connected to the first input terminal of the PWM signal generator 6 and outputs the U-phase modulation signal Su to the PWM signal generator 6.

[0049] The second output terminal of the modulation signal switch 4 is connected to the second input terminal of the PWM signal generator 6, and outputs the V-phase modulation signal Sv to the PWM signal generator 6. The third output terminal of the modulation signal switch 4 is connected to the third input terminal of the PWM signal generator 6, and outputs the W-phase modulation signal Sw to the PWM signal generator 6.

[0050] The carrier wave generator 5 generates a carrier wave Sc of a predetermined frequency (predetermined period) based on the carrier wave command fc. This carrier wave Sc is, for example, a triangular wave of a predetermined frequency (predetermined period). The carrier wave generator 5 has an output terminal in addition to the input terminal described above. The output terminal of the carrier wave generator 5 is connected to the fourth input terminal of the PWM signal generator 6 and outputs the carrier wave Sc to the PWM signal generator 6.

[0051] The PWM signal generator 6 generates first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz by comparing the U-phase modulated signal Su, V-phase modulated signal Sv, and W-phase modulated signal Sw with the carrier wave Sc. This PWM signal generator 6 has six output terminals in addition to the first to fourth input terminals described above. These six output terminals are the first to sixth output terminals of the inverter control device B described above.

[0052] That is, the PWM signal generator 6 outputs a first PWM signal Gu from a first output terminal to the inverter C, outputs a second PWM signal Gv from a second output terminal to the inverter C, and outputs a third PWM signal Gw from a third output terminal to the inverter C. Furthermore, the PWM signal generator 6 outputs a fourth PWM signal Gx from a fourth output terminal to the inverter C, outputs a fifth PWM signal Gy from a fifth output terminal to the inverter C, and outputs a sixth PWM signal Gz from a sixth output terminal to the inverter C.

[0053] Next, the operations of the motor drive device A and the inverter control device B according to this embodiment will be described.

[0054] First, an outline of the overall operation of the motor drive device A and the inverter control device B will be described. In the motor drive device A, the inverter control device B controls the target torque T ０ and inverter fundamental frequency f ０ The first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz are generated based on the above.

[0055] Then, the inverter control device B outputs the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz to the inverter C. The inverter C generates a U-phase drive signal Ku, a V-phase drive signal Kv, and a W-phase drive signal Kw by converting DC power supplied from the battery pack into AC power based on the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz.

[0056] The inverter C outputs a U-phase drive signal Ku, a V-phase drive signal Kv, and a W-phase drive signal Kw to the motor D, thereby driving the motor D to rotate. That is, the motor D generates a target torque T ０ It rotates with a torque according to the

[0057] Here, the target torque T ０ (torque generated by motor D) and inverter fundamental frequency f ０ The relationship between the target torque T ０ and inverter fundamental frequency f ０ The operating region (frequency region) of the inverter control device B, that is, one of the regions 1 to 6, is selected by the above.

[0058] That is, in the inverter control device B, the command value generator 1 calculates the target torque T ０ and inverter fundamental frequency f ０ The command value generator 1 generates a frequency domain command Z that specifies one of the regions 1 to 6 based on the above. Then, the command value generator 1 outputs this frequency domain command Z to the modulation signal switcher 4.

[0059] The command value generator 1 also calculates the target torque T ０ and inverter fundamental frequency f ０ The command value generator 1 generates a modulating signal frequency command f and a modulation factor M based on the above and outputs them to the first modulating signal generator 2 and the second modulating signal generator 3, and similarly generates a square wave superposition factor γ and outputs it to the second modulating signal generator 3. Furthermore, the command value generator 1 similarly generates a carrier wave command fc and outputs it to the carrier wave generator 5.

[0060] On the other hand, in the inverter control device B, the first modulation signal generator 2 generates a U-phase element modulation signal Su1, a V-phase element modulation signal Sv1, and a W-phase element modulation signal Sw1 (see FIGS. 4(a) and 4(b)) for asynchronous PWM control or synchronous PWM control corresponding to any one of regions 1 to 3 based on the modulation signal frequency command f and the modulation factor M in addition to the frequency domain command Z, and outputs these to the modulation signal switcher 4.

[0061] Furthermore, the second modulation signal generator 3 generates a U-phase element modulation signal Su2, a V-phase element modulation signal Sv2, and a W-phase element modulation signal Sw2 (see Figures 4(c) to 4(d)) for synchronous PWM control corresponding to any one of regions 4 to 6 based on the modulation signal frequency command f, modulation factor M, and square wave superposition rate γ in addition to the frequency domain command Z, and outputs these to the modulation signal switcher 4.

[0062] Then, the modulation signal switcher 4 generates a U-phase element modulation signal Su1, a V-phase element modulation signal Sv1, and a W-phase element modulation signal Sw1 or a U-phase element modulation signal Su2, a V-phase element modulation signal Sv2, and a W-phase element modulation signal Sw2 based on the frequency domain command Z, and outputs the U-phase modulation signal Su, V-phase modulation signal Sv, and W-phase modulation signal Sw corresponding to any of regions 1 to 6 to the PWM signal generator 6 by selecting the modulation signal switcher 4.

[0063] On the other hand, the carrier wave generator 5 generates a carrier wave Sc based on the carrier wave command fc and outputs it to the PWM signal generator 6. Then, the PWM signal generator 6 generates first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz based on comparison of the U-phase modulated signal Su, the V-phase modulated signal Sv, and the W-phase modulated signal Sw with the carrier wave Sc.

[0064] Here, if the frequency domain command Z specifies region 4, the U-phase modulation signal Su, V-phase modulation signal Sv, and W-phase modulation signal Sw input to the PWM signal generator 6 are trapezoidal wave modulation signals as shown in Fig. 4C. As shown in Fig. 5A, the PWM signal generator 6 generates first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz by comparing the trapezoidal wave modulation signals with the carrier wave Sc (triangular wave).

[0065] In this case, the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz contain nine pulses in one period of the trapezoidal wave modulation signal, as shown in FIG. ０ is relatively small, and the inverter fundamental frequency f ０ In a region 4 where the amplitude is relatively high, the inverter C is synchronously PWM controlled by the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz of nine pulses generated by comparing the trapezoidal wave modulation signal with the triangular wave.

[0066] This trapezoidal wave modulation signal has a shape in which the central portion (corresponding to 120 degrees) in a half cycle is a flat portion of the DC voltage Ed, and the portions in front of the central portion (corresponding to 30 degrees) and the front portions (corresponding to 30 degrees) are linearly inclined. ｕｖｍ is expressed by the following equation (1) with DC voltage Ed and modulation factor M as variables. Note that modulation factor M is a value smaller than "1". ｕｖｍ　 = 1.05ME ｄ (1)

[0067] Furthermore, when the frequency domain command Z specifies region 5, the U-phase modulation signal Su, V-phase modulation signal Sv, and W-phase modulation signal Sw input to the PWM signal generator 6 are modified trapezoidal wave modulation signals as shown in Fig. 4D. As shown in Fig. 5B, the PWM signal generator 6 generates first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz by comparing the modified trapezoidal wave modulation signal with the carrier wave Sc (triangular wave).

[0068] In this case, the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz contain five pulses in one period of the modified trapezoidal wave modulation signal, as shown in FIG. ０ is smaller than that in region 4, and the inverter fundamental frequency f ０ In region 5 where is higher than region 4, inverter C is synchronously PWM controlled by first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz of five pulses generated by comparing the modified trapezoidal wave modulated signal with a triangular wave.

[0069] This modified trapezoidal wave modulated signal has a central portion in which a square wave of an amplitude according to the square wave superposition rate γ is superimposed on a 120 degree equivalent portion (DC voltage Ed) in one half cycle of the trapezoidal wave modulated signal described above, and the front portion (30 degree equivalent portion) and the front portion (30 degree equivalent portion) of the central portion have a linearly inclined shape.

[0070] The three-phase AC line voltage amplitude V corresponding to such a modified trapezoidal wave modulation signal is ｕｖｍ is expressed by the following equation (2) with DC voltage Ed, modulation factor M, and square wave superposition factor γ as variables. In this case, the modulation factor M is "1", and the number of pulses is set to 5 pulses by the square wave superposition factor γ.

[0071]

[0072] Furthermore, when the frequency domain command Z specifies region 6, the U-phase modulation signal Su, V-phase modulation signal Sv, and W-phase modulation signal Sw input to the PWM signal generator 6 are trapezoidal wave modulation signals as shown in Fig. 4E. As shown in Fig. 5C, the PWM signal generator 6 generates first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz by comparing the trapezoidal wave modulation signals with the carrier wave Sc (triangular wave).

[0073] In this case, the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz contain one pulse per period of the trapezoidal wave modulation signal, as shown in FIG. ０ In region 6 where is higher than region 5, the inverter C is synchronously PWM controlled by first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz, each of which has one pulse and is generated by comparing the trapezoidal wave modulation signal with a triangular wave.

[0074] This trapezoidal wave modulation signal is the same as that in the case of the above-mentioned region 4, and the central portion (corresponding to 120 degrees) in the half cycle is a flat portion of the DC voltage Ed, and the front portions (corresponding to 30 degrees) and the front portions (corresponding to 30 degrees) of the central portion have a linearly inclined shape. ｕｖｍ is expressed by the above equation (1) with the DC voltage Ed and the modulation factor M as variables, and the number of pulses is set to one pulse by the modulation factor M.

[0075] The inverter control device B of this embodiment generates first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz that PWM control the inverter C based on a comparison of the U-phase modulated signal Su, the V-phase modulated signal Sv, and the W-phase modulated signal Sw with the carrier wave Sc.

[0076] The inverter control device B according to this embodiment also includes a first modulation signal generator 2 and a second modulation signal generator 3 that generate a plurality of U-phase element modulation signals Su1, V-phase element modulation signals Sv1, W-phase element modulation signals Sw1, U-phase element modulation signals Su2, V-phase element modulation signals Sv2, and W-phase element modulation signals Sw2 that set the modulation factor M and the number of pulses of the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz; 2. A modulation signal switch 4 that alternatively selects the V-phase element modulation signal Sv2 and the W-phase element modulation signal Sw2 and outputs them as the U-phase modulation signal Su, the V-phase modulation signal Sv, and the W-phase modulation signal Sw, a carrier wave generator 5 that generates a carrier wave Sc, and a PWM signal generator 6 that generates the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz based on the U-phase modulation signal Su, the V-phase modulation signal Sv, and the W-phase modulation signal Sw input from the modulation signal switch 4 and the carrier wave Sc input from the carrier wave generator 5.

[0077] According to this embodiment, the number of pulses of the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz is set by selecting one of a plurality of U-phase element modulation signal Su1, V-phase element modulation signal Sv1, W-phase element modulation signal Sw1, U-phase element modulation signal Su2, V-phase element modulation signal Sv2, and W-phase element modulation signal Sw2. Therefore, according to this embodiment, it is possible to provide an inverter control device B that can simplify software processing for generating the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz while suppressing pulsation in the drive current of the motor C.

[0078] In the inverter control device B according to this embodiment, the element modulation signal used in synchronous PWM control of the inverter C is a trapezoidal wave signal or a modified trapezoidal wave signal in which a square wave is superimposed on the trapezoidal wave signal. According to this embodiment, by using the trapezoidal wave signal or the trapezoidal wave signal, it is possible to achieve synchronous PWM control of the inverter C while suppressing pulsation in the drive current of the motor C, even with simplified software processing.

[0079] In addition, the inverter control device B according to this embodiment is configured to control the target torque T ０ decreases, U-phase element modulation signal Su1, V-phase element modulation signal Sv1, W-phase element modulation signal Sw1, U-phase element modulation signal Su2, V-phase element modulation signal Sv2, and W-phase element modulation signal Sw2 are switched to reduce the number of pulses of the fourth to sixth PWM signals Gx, Gy, and Gz, thereby performing synchronous PWM control of the inverter C. According to this embodiment, it is possible to perform synchronous PWM control of the inverter C while suppressing pulsation of the drive current of the motor C and suppressing loss (switching loss) of the inverter C.

[0080] Furthermore, the inverter control device B according to this embodiment reduces the number of pulses of the fourth to sixth PWM signals Gx, Gy, and Gz in the order of 9, 5, and 1. According to this embodiment, it is possible to more accurately suppress pulsation in the drive current of the motor C, and also to perform synchronous PWM control of the inverter C while suppressing loss (switching loss) in the inverter C. Note that instead of reducing the number of pulses in the order of 9 pulses → 5 pulses → 1 pulse as described above, the number of pulses may be reduced in the order of 9 pulses → 7 pulses → 5 pulses → 1 pulse, or in the order of 9 pulses → 7 pulses → 1 pulse, for example.

[0081] Furthermore, the motor drive device A according to this embodiment includes an inverter control device B, and an inverter C that is controlled by the inverter control device B and outputs a U-phase drive signal Ku, a V-phase drive signal Kv, and a W-phase drive signal Kw to the motor D. According to this embodiment, it is possible to provide a motor drive device A that can simplify the software processing for generating the first to sixth PWM signals Gu, Gv, Gw, Gx, Gy, and Gz while suppressing pulsation in the drive current of the motor C.

[0082] The present disclosure can be used in an inverter control device B that controls an inverter C, and a motor drive device A that includes the inverter control device B and the inverter C.

[0083] A Motor drive device B Inverter control device C Inverter D Motor Gu, Gv, Gw, Gx, Gy, Gz PWM signals Ku, Kv, Kw Drive signals 1 Command value generator 2 First modulation signal generator 3 Second modulation signal generator 4 Modulation signal switcher 5 Carrier wave generator 6 PWM signal generator

Claims

1. An inverter control device that controls an inverter that converts DC voltage to AC voltage and outputs it to a motor, comprising: a carrier wave generation unit that generates a carrier wave; multiple types of modulation signals according to the number of pulses of a PWM pulse signal; and a PWM control unit that pulse-width modulates a voltage command using the carrier wave and the modulation signal to generate a PWM pulse signal for controlling the operation of the inverter, wherein the PWM control unit keeps the frequency of the carrier wave constant in a predetermined rotation speed range of the motor, and switches between multiple types of modulation signals to switch the number of pulses of the PWM pulse signal while maintaining the frequency ratio between the carrier wave and the modulation signal.

2. The inverter control device according to claim 1, wherein the modulating signal when the inverter is subjected to synchronous PWM control is a trapezoidal wave signal or a modified trapezoidal wave signal in which a square wave is superimposed on the trapezoidal wave signal.

3. An inverter control device according to claim 1 or 2, wherein when the inverter fundamental frequency becomes high, the number of pulses is reduced by switching the modulation signal, thereby performing synchronous PWM control of the inverter.

4. The inverter control device according to claim 3, wherein the number of pulses is decreased in the order of 9, 5, and 1.

5. A motor drive device comprising the inverter control device according to claim 1 or 2, and an inverter controlled by the inverter control device and outputting a drive signal to a motor.

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