JP2008271617A - Power conversion device and control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion device wherein it is possible to maintain the same waveform characteristic as conventional three-phase modulation types even in the low-speed range of a load motor 2 and to achieve stable driving and reduce electromagnetic waves. <P>SOLUTION: Triangular-wave carriers are independently generated on a phase-by-phase basis by U- to W-phase triangular wave generation units 6u to 6w independent on a phase-by-phase basis, and a phase difference is provided therebetween. Using a microcomputer or the like as a computing device 3, operation of temporarily updating and setting buffers 9u to 9w is carried out with timing different from phase to phase to compare the voltage command values Vu* to Vw* of the respective phases with a triangular wave. The frequency of the carrier of each phase is individually adjusted based on information such as the output voltage of the power conversion device and acceleration. Switching driving is carried out so that changes in the PWM pulses of output voltage do not overlap. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power converter and a control method thereof, and more particularly to a power converter and a control method thereof that reduce electromagnetic noise generated by a power converter.

  There are concerns about adverse effects such as malfunction of peripheral devices due to electromagnetic interference (EMI) generated by the power converter. As a countermeasure against this, a method such as attaching a passive component such as a common mode choke is generally implemented, but an increase in the size and cost of the apparatus cannot be avoided. Electromagnetic interference increases particularly when the load motor is driven at an extremely low speed, that is, when the output voltage amplitude of the power converter is close to zero. This is because all the switches of the three-phase inverter are turned ON / OFF almost simultaneously, so that the zero-phase voltage is remarkably increased.

  On the other hand, in the two-phase modulation type inverter device disclosed in Patent Document 1, the number of simultaneously switched phases is reduced to 2/3 by adopting a two-phase modulation method in which only two of the three phases are switched. Reduce noise to reduce noise. Further, in Patent Document 1, taking advantage of the characteristics of the two-phase modulation type, a two-phase command value to be switched with respect to the same triangular wave carrier when generating a PWM pulse is set to ON when one is larger than the triangular wave, The other is set to ON when it is small. This shifts the center point of the PWM pulse, avoids simultaneous switching of a plurality of phases, and reduces noise even outside the extremely low speed range.

  Patent Documents 2-5 disclose a method of shifting the phase of the output voltage as a capacitor ripple reduction technique, a motor loss reduction technique, and a conversion efficiency improvement measure.

JP 2003-33042 A JP 2004-187386 A JP 2002-27763 A JP 2004-248419 A JP 2005-224070 A

  However, in the two-phase modulation method of Patent Document 1, since the width of a PWM (Pulse Width Modulation) pulse is extremely narrow in the low speed region of the load motor, the device may not react and the waveform distortion may increase. is there. In particular, in systems such as elevators that require low-speed and high-torque drive characteristics, waveform characteristic deterioration due to waveform distortion has a significant effect on ride comfort. In addition, when a narrow PWM pulse is repeatedly applied to the device, the device may be damaged.

  On the other hand, in Patent Document 2-5, a PWM pulse equivalent to the conventional three-phase modulation method can be output, but there is a possibility of malfunction, and in practical use, in order to ensure its stable operation, Ingenuity is necessary. Further, depending on the magnitude of the voltage command value, a plurality of phases may be switched at the same time to cause electromagnetic wave interference.

  An object of the present invention is to provide a power conversion device capable of reducing electromagnetic waves with stable driving and a control method thereof while maintaining waveform characteristics equivalent to those of a conventional three-phase modulation method.

  In one aspect of the present invention, as an arithmetic unit that transmits a pulse-width-modulated PWM signal to a drive circuit that drives a switching element in a power converter, the voltage command value to the power converter is set to a phase difference for each phase. A comparison unit that compares the triangular wave with the triangular wave, and the update timing of the voltage command value to be compared with the triangular wave is configured to be executed at a timing for each phase corresponding to the phase of the triangular wave for each phase. Features.

  In a preferred embodiment of the present invention, the voltage command is temporarily stored for comparison with a primary storage unit for each phase for temporarily storing the voltage command value and the triangular wave independent for each phase. A primary storage unit for each phase, and command transfer for transferring the voltage command value stored in the primary storage unit to the primary storage unit at a timing for each phase corresponding to the phase of the triangular wave for each phase A processing unit is provided.

  In a more specific embodiment, a triangular wave carrier used for PWM pulse generation is provided independently for each phase, and a phase difference is provided for each triangular wave carrier.

  Further, a digital arithmetic device such as a microcomputer is used as the arithmetic device, and in order to compare the command value of each phase with a triangular wave, a buffer to be temporarily stored is set at a different timing.

  Furthermore, the frequency of the carrier of each phase is individually adjusted based on information such as the output voltage and acceleration of the power converter, and driving is performed so as to avoid simultaneous switching of PWM pulses of the output voltage.

  According to a preferred embodiment of the present invention, a sufficient width of a PWM pulse can be secured in a low speed region, so that waveform characteristics equivalent to those of a conventional three-phase modulation method can be secured, and electromagnetic waves can be reduced. In particular, it is effective in a power conversion device that has a switching device that can be driven at a high speed and is driven at a high switching frequency.

  Other objects and features of the present invention will become apparent in the description of the embodiments described below.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a main circuit and a control system of a power conversion device according to an embodiment of the present invention. The main circuit includes an inverter main circuit unit 1 constituted by switching elements, and an AC motor 2 as a load driven by the main circuit unit 1 supplied with AC of variable voltage and variable frequency. As a control system, the main circuit unit 1 is calculated based on a calculation device 3 for calculating a signal for driving the main circuit unit 1 to cause the load 2 to perform a desired operation, and a signal output from the calculation device 3. And a drive circuit 4 for driving the. The arithmetic device 3 is constituted by an arithmetic processing device such as a microcomputer, an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit). The inside includes a voltage command value generation unit 5 that generates output voltage command values Vu * to Vw * for each phase of U to W from a current flowing through the load 2, a triangular wave generation unit 6u to 6w that generates a triangular wave carrier, and And comparison processing units 7u to 7w that generate PWM pulses Vupwm to Vwpwm by comparing the command values Vu * to Vw * with the triangular wave signals Tru to Trw.

  In the conventional system, the components of the power converter are almost the same as those in the embodiment of FIG. However, in the arithmetic unit 3, a single triangular wave generation unit is used for generating a triangular wave carrier, and a single triangular wave signal Tr1 generated by the triangular wave generation unit 61 in the comparison processing units 7u to 7w of each phase The voltage command values Vu * to Vw * were compared.

  Next, a specific configuration of the voltage command value generation unit 5 in the embodiment of FIG. 1 will be described.

  FIG. 2 is a functional explanatory diagram of the arithmetic device 3 showing an example of data transfer in the voltage command value generation unit 5 according to one embodiment of the present invention. First, a voltage command value calculation unit 8 that calculates voltage command values Vu * to Vw * of each phase is provided, and buffer registers 9u to 9w that temporarily store the calculated voltage command values Vu * to Vw * are provided. Yes. Then, the command transfer processing units 10u to 10w that transfer the voltage command values stored in these buffer registers at predetermined timings, and the voltage command values transferred from these are stored, and are compared with the triangular wave. It consists of set registers 11u to 11w for giving voltage command values.

  The voltage command value stored in the set register and the triangular wave signals Tru to Trw output from the triangular wave generating units 6u to 6w are compared in the comparison processing units 7u to 7w, and PWM pulses Vupwm to Vwpwm are generated.

  Here, since the arithmetic device 3 is a digital arithmetic processing device such as a microcomputer, FPGA, or ASIC, a signal to be handled is also a discrete signal. For this reason, the timing of the change of the discrete signal becomes important. Details of the operation will be described later.

  FIG. 3 is an example of an output PWM waveform and a zero-phase voltage waveform in the conventional method. FIG. 3A is a schematic diagram of a triangular wave comparison method, and FIG. 3B is an output PWM waveform and a zero-phase voltage waveform. For example, when attention is paid to the U-phase output voltage command value Vu * in FIG. 3A, the U-phase output voltage Vu is in the Hi state (Vu = Ed) when the formula (1) is established in the one-dot chain line portion. .

Vu * ≧ Tr1 ………………………………………………………………………… (1)
Further, when the expression (2) is satisfied, a PWM pulse is generated so that Vu is in the Lo state (Vu = 0).

Vu * <Tr1 ………………………………………………………………………… (2)
On the other hand, the zero-phase voltage Vo that affects the electromagnetic wave is given as equation (3), and the amount of noise increases in proportion to the change width of the zero-phase voltage Vo.

Vo = (Vu + Vv + Vw) / 3 …………………………………………………… (3)
Here, Vu to Vw are U to W phase output voltages.

  That is, in the normal switching state, from equation (3), the zero-phase voltage Vo varies by Ed / 3 every time each phase switch is switched, but a plurality of phases as shown by the broken-line ellipse in FIG. When fluctuates simultaneously, the fluctuation range of the zero-phase voltage Vo increases and the amount of noise increases.

  FIG. 4 is an example of an output PWM waveform and a zero-phase voltage waveform when a zero voltage is output in the conventional method. FIG. 4A is a schematic diagram of a triangular voltage comparison method for zero voltage output, and FIG. 4B shows an output PWM waveform and a zero phase voltage waveform. When the load is driven at an extremely low speed, the state is close to a zero voltage output state. As shown in FIG. 4B, the output voltages Vu to Vw of each phase have almost the same waveform. As a result, the line voltage on the output side of the power converter becomes zero. However, the zero-phase voltage Vo in this case is expressed by equation (4) by the dotted line portion in FIG.

Vo = Ed ……………………………………………………………………………… (4)
For this reason, compared with the case where a single phase switches, a noise amount increases about 3 times.

  The above is the case of three-phase modulation, but in the two-phase modulation method, one of the three phases is always fixed to the ON state or OFF state, and only two phases are switched. The voltage Vo is expressed by equation (5), and the amount of noise can be reduced as compared with the case of three-phase modulation.

Vo = 2 ・ Ed / 3 …………………………………………………………………… (5)
However, when paying attention to the waveform at the time of zero voltage output, in the case of three-phase modulation, the duty ratio (ratio of ON time to OFF time) is about 50% as shown in FIG. In the case of two-phase modulation, the duty ratio becomes extremely small and the device cannot respond completely. As a result, the waveform distortion may increase. Particularly in systems such as elevators that require low-speed and high-torque drive characteristics, waveform characteristic deterioration due to waveform distortion has a significant effect on ride comfort. In addition, when a narrow PWM pulse is repeatedly applied to the device, the device may be damaged.

  On the other hand, in one embodiment of the present invention shown in FIG. 1, triangular wave generators 6u to 6w for generating triangular wave carriers are provided independently for each phase, and furthermore, for the triangular wave signals Tru to Trw to be output respectively. A phase difference is provided.

  FIG. 5 is an example of an output PWM waveform and a zero-phase voltage waveform in the embodiment of the present invention shown in FIGS. 1 and 2, and FIG. 5A is a schematic diagram of a triangular wave comparison method, and FIG. Are the output PWM waveform and the zero-phase voltage waveform. FIG. 5A shows an example in which a phase difference of 120 degrees is provided for each phase triangular wave signal. In this case, the duty ratio of the output voltage waveform is substantially the same as in FIG. 3, and the change width of the zero-phase voltage Vo is approximately expressed by the equation (6).

Vo = Ed / 3 …………………………………………………………………… (6)
On the other hand, FIG. 6 shows an example of an output PWM waveform and a zero-phase voltage waveform at the time of zero voltage output in the embodiment. FIG. 6A is a schematic diagram of a triangular voltage comparison method for zero voltage output, and FIG. 6B shows an output PWM waveform and a zero phase voltage waveform. In this case, the duty ratio of the output voltage waveform is about 50% as in the case of FIG. Further, due to the effect of providing a phase to the triangular wave signal, the change width of the zero-phase voltage Vo becomes the expression (7), and noise can be reduced even when the zero voltage is output.

Vo = Ed / 3 ………………………………………………………………………… (7)
In FIG. 6, when viewed on the time axis of the carrier cycle level, the output line voltage fluctuates instead of zero. However, when viewed on the time axis of the tens of ms level that is the output frequency level of the load, the duty ratio is approximately 50%, so the output line voltage becomes zero on average. In particular, in a power converter having a switching device that can be driven at high speed, the waveform is extremely accurate when the frequency of the triangular wave carrier is high.

  FIG. 7 is an example of a case where a malfunction may occur in the comparison process when the comparison between the U-phase command value Vu * and the U-phase triangular wave signal Tru is taken as an example. 7, the U-phase voltage command value Vu * is changing at a timing overlapping with the change of the U-phase triangular wave signal Tru. In other words, the voltage command value is not stable at the timing (between peaks and valleys) at which it should be detected that the magnitude relationship between the voltage command value and the triangular wave signal is reversed (changed), and the magnitude relationship between the two is discriminated. May become difficult and may cause malfunction.

  FIG. 8 is a waveform diagram for explaining the operation for updating the voltage command value for comparison in accordance with the vicinity of the peaks and valleys of the triangular wave signal in one embodiment of the present invention. This process corresponds to the timing of transfer by the command transfer processing units 10u to 10w being set near the peaks and valleys of the triangular wave signal.

  In the conventional arithmetic unit, since it is compared with a single triangular wave, the voltage command values stored in the buffer registers of all phases are converted to a peak of the triangular wave signal as shown in FIG. It was transferred according to the position of the valley.

  On the other hand, in the case of one embodiment of the present invention, each phase has triangular wave generation units 6u to 6w, and each phase is different, so that processing is performed by a single command transfer processing unit. Is in a state as shown in FIG. 7 in any phase, and may cause malfunction. Therefore, in this embodiment, the command transfer processing units 10u to 10w are provided in each phase, and the command transfer processing units 10u to 10w of each phase are different, that is, near the peaks and valleys of the triangular wave signal of each phase. Command transfer is executed at the individual position. As a result, each phase has a relationship as shown in FIG. 8, and it is possible to prevent a malfunction from occurring during the triangular wave comparison.

  Further, in FIGS. 5 and 6, the phase difference between the triangular wave signals Tru to Trw of each phase is 120 degrees. However, the purpose of simultaneous switching in the zero voltage state is not limited to 120 degrees. That is, the phase difference of the triangular wave signal of each phase may be non-uniformly spaced. In particular, the common mode current generated due to the change in the zero-phase voltage, that is, the current that directly causes electromagnetic interference is a waveform that dampens at a frequency of several tens of kHz to several MHz. If the phase is only shifted, it can be said that there is a sufficient noise reduction effect.

  The embodiment of the present invention as described above is summarized as follows.

  First, a power converter in which the main circuit 1 is configured using a semiconductor switching element, a drive circuit 4 that drives the switching element in the power converter, and a PWM signal Vupwm that is pulse-width modulated in the drive circuit 4 ˜Vwpwm is provided. As shown in FIG. 1, the arithmetic device 3 includes a voltage command value generation unit 5 that generates voltage command values Vu * to Vw * to the power converter, and each of the voltage command values Vu * to Vw *. Comparing units 7u to 7w for comparing with triangular waves Tru to Trw having a phase difference for each phase are provided. Here, as shown in FIG. 2, the arithmetic device 3 first stores the buffer command 9u-9w for each phase for temporarily storing the voltage command values Vu * -Vw * calculated by the voltage command value calculation unit 8. It has. In addition, in order to compare with the triangular waves Tru to Trw for each phase, there are provided set registers 11u to 11w for each phase for temporarily storing the voltage command values Vu * to Vw *. Further, as shown in FIG. 8, the latest values of the voltage commands Vu * to Vw * stored in the buffer registers 9u to 9w are set according to the phases near the peaks and valleys of the triangular wave for each phase. Command transfer for transferring to the set registers 11u to 11w at the timing of each phase and updating the voltage command values Vu * to Vw * in the set registers 11u to 11w to be compared with the triangular waves Tru to Trw Processing units 10u to 10w are provided.

  As a result, the set registers 11u to be compared with the triangular wave carriers Tru to Trw of each phase as described with reference to FIG. 8 even though the triangular wave carriers Tru to Trw of each phase have a phase shift. The voltage commands Vu * to Vw * in ˜11w are updated only in the vicinity of the peaks and valleys of the triangular wave carriers Tru to Trw of each phase. Therefore, at the timing (between peaks and valleys) at which the magnitudes of the triangular wave carriers Tru to Trw of each phase and the magnitudes of the voltage commands Vu * to Vw * are reversed (changed), the voltage commands Vu * to Vw * are always set. The size is stable. Therefore, the operations of the comparison units 7u to 7w are also stable, and PWM modulation without fear of malfunction can be realized.

  Next, the operation of the triangular wave generators 6u to 6W in the embodiment of FIGS. 1 and 2 will be described.

  With the processing of FIG. 2, even when driving with the same frequency and driving with the same phase difference in the triangular wave signal generated by the triangular wave generating section of each phase, the generated noise is small and stable driving can be achieved particularly in the zero voltage region. However, there may be a phase that switches at the same time as the voltage command value increases. In order to avoid this, in this embodiment, the phase of the triangular wave signal of each phase is changed in preparation for the voltage value in the case of simultaneous switching based on the magnitude of the commanded output voltage and the acceleration information of the load motor. . Generally, since a power converter outputs a balanced voltage, it is possible to know in advance the voltage value of each phase when switching simultaneously. Furthermore, when the load acceleration and operation pattern can be grasped to some extent, such as in an elevator, it is possible to avoid simultaneous switching in all output voltage regions by performing a feedforward change in the phase of the triangular wave signal. This is effective in reducing noise.

  FIG. 9 is a diagram showing a carrier state when the carrier phase is changed in one embodiment of the present invention. While the U-phase triangular wave signal Tru is a triangular wave signal having the same frequency, the V-phase triangular wave signal Trv temporarily increases the triangular wave frequency in the phase fluctuation section and has a phase higher than that of the U-phase triangular wave signal Tru. Proceed. On the other hand, the triangular wave signal Trw for the W phase is delayed in phase with respect to the triangular wave signal Tru for the U phase by temporarily lowering the triangular wave frequency in the phase fluctuation section. When a triangular wave signal is generated by a microcomputer or the like, generally, a process of counting up the clock signal and counting down when the turn-up level trn1 is reached is taken. Therefore, the triangular wave frequency can be increased by lowering the level value like the folding level trn2, and the triangular wave frequency can be lowered by raising the level value like the folding level trn3.

  FIG. 10 is a diagram showing the relationship between the output value and the carrier amplitude in FIG. When the amplitude of the triangular wave is changed as in the broken line ellipse of the triangular wave signal in FIG. 9, the voltage command value needs to be adjusted accordingly. In the case where the DC voltage value of the main circuit unit 1 in FIG. 1 is Ed and the number of clocks of the triangular wave half cycle is A as shown in FIG. The voltage command value can be adjusted by multiplying the gain and adjusting the offset by A / 2 [digit].

Ed [V] = A [digit] ... ……………………………………………… (8)
Although one embodiment of the present invention has been described by taking a three-phase inverter as an example, the same effect can be obtained even in the case of a three-phase PWM rectifier or a bridge-type single-phase power converter. Needless to say.

  As mentioned above, although one Example of this invention was described, this invention is not limited to said Example, It cannot be overemphasized that it can implement variously within the range which does not change the summary.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the main circuit and control system of the power converter device by one Example of this invention. It is function explanatory drawing of the arithmetic unit 3 which shows the example of the data transfer in the command value generation part by one Example of this invention. The example of the output PWM waveform and zero phase voltage waveform in a conventional system. The example of the output PWM waveform and zero phase voltage waveform at the time of zero voltage output by the conventional system. The example of the output PWM waveform and zero phase voltage waveform in one Example of this invention. The output PWM waveform and zero phase voltage waveform at the time of the zero voltage output in one Example of this invention. An example in which a malfunction may occur in the comparison process when the comparison between the U-phase command value Vu * and the U-phase triangular wave signal Tru is taken as an example. The waveform diagram for operation | movement description which updates a command value according to the position of the peak or trough of the triangular wave signal in one Example of this invention. The figure which shows the carrier state in the case of changing a carrier phase in one Example of this invention. The figure which shows the relationship between the output value and carrier amplitude in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Main circuit part, 2 ... Load (motor), 3 ... Arithmetic unit, 4 ... Drive circuit, 5 ... Voltage command value generation part, 6u-6w ... Triangle wave generation part for U-W phase, 61 ... Triangle wave generation part, 7u-7w ... U-W phase comparison processing unit, 8 ... Voltage command value calculation unit, 9u-9w ... U-W phase buffer register, 10u-10w ... U-W phase command transfer processing unit, 10u-10w ... U to W phase command transfer unit, 11u to 11w ... U to W phase set register, Vu to Vw ... U to W phase output voltage, Vo ... Zero phase voltage, Vu * to Vw * ... U to W phase output Voltage command value, Vupwm-Vwpwm ... U-W phase PWM pulse, Tr1 ... Triangular wave signal, Tru-Trw ... U-W phase triangular wave signal.

Claims (18)

  A power converter having a main circuit using a semiconductor switching element, a drive circuit for driving the switching element in the power converter, and an arithmetic unit for transmitting a pulse width modulated PWM signal to the drive circuit The arithmetic device includes a voltage command value generation unit that generates a voltage command value for the power converter, and a comparison unit that compares the voltage command value with a triangular wave having a phase difference for each phase. In the power converter, the arithmetic unit is configured to execute the update timing of the voltage command value to be compared with the triangular wave at a timing for each phase corresponding to the phase of the triangular wave for each phase. A power conversion device.   A power converter having a main circuit using a semiconductor switching element, a drive circuit for driving the switching element in the power converter, and an arithmetic unit for transmitting a pulse width modulated PWM signal to the drive circuit The arithmetic device includes a voltage command value generation unit that generates a voltage command value for the power converter, and a comparison unit that compares the voltage command value with a triangular wave having a phase difference for each phase. In the power converter, the arithmetic unit temporarily stores the voltage command value for comparison with a primary storage unit for each phase that temporarily stores the voltage command value and the triangular wave for each phase. A primary storage unit for each phase to be stored, and a command for transferring the voltage command value stored in the primary storage unit to the primary storage unit at a timing for each phase corresponding to the phase of the triangular wave for each phase Equipped with a transfer processing unit Power converter, wherein the door.   3. The power conversion device according to claim 1, wherein the arithmetic device is a digital arithmetic processing device such as a microcomputer, FPGA, or ASIC.   4. The power conversion device according to claim 2, wherein the primary storage unit includes a buffer register.   The power converter according to claim 2, wherein the primary storage unit includes a set register.   The calculation device according to any one of claims 2 to 5, further comprising a triangular wave generation unit for each phase that generates a triangular wave for each phase each having a phase difference, and the command transfer processing unit includes: A power converter configured to generate a transfer command at different timings independently of each other.   7. The power conversion device according to claim 2, wherein the command transfer processing unit is configured to transfer a command value near a peak or valley of a triangular wave signal of each phase.   The frequency setting unit that sets the frequency of the triangular wave signal generated by the triangular wave generation unit of each phase independently for each phase and the phase difference between the triangular wave signals of each phase according to any one of claims 1 to 7 A power conversion device comprising a phase adjustment unit.   9. The power converter according to claim 1, further comprising a phase difference adjustment unit that adjusts the phase difference so that all of the PWM signals change at different timings.   10. The on / off ratio according to any one of claims 1 to 9, wherein the PWM signals of each phase are substantially 50% of the voltage command values at which the voltage command values of all phases are substantially zero. And the phase of each phase PWM signal is different from each other.   A power converter having a main circuit using a semiconductor switching element, a drive circuit for driving the switching element in the power converter, and an arithmetic unit for transmitting a pulse width modulated PWM signal to the drive circuit The arithmetic device includes a voltage command value generation unit that generates a voltage command value for the power converter, and a comparison unit that compares the voltage command value with a triangular wave having a phase difference for each phase. In the power converter, the arithmetic unit temporarily stores the voltage command value for comparison with a buffer register for each phase that temporarily stores the voltage command value and the triangular wave for each phase. The latest value of the voltage command stored in the set register for each phase and the buffer register is set at the timing for each phase according to the phase near the peak and the valley of the triangular wave for each phase. And transferred to the register, a power conversion apparatus characterized by comprising a command transfer processing unit for updating the voltage command value in the set register to be compared with the triangular wave.   A power converter having a main circuit using a semiconductor switching element, a drive circuit for driving the switching element in the power converter, and an arithmetic unit for transmitting a pulse width modulated PWM signal to the drive circuit A voltage command value generation step for generating a voltage command value for the power converter, and a comparison step for comparing the voltage command value with a triangular wave having a phase difference for each phase. In the control method, the update method of the voltage command value to be compared with the triangular wave is executed at a timing for each phase corresponding to the phase of the triangular wave for each phase.   A power converter having a main circuit using a semiconductor switching element, a drive circuit for driving the switching element in the power converter, and an arithmetic unit for transmitting a pulse width modulated PWM signal to the drive circuit A voltage command value generation step for generating a voltage command value for the power converter, and a comparison step for comparing the voltage command value with a triangular wave having a phase difference for each phase. In the control method, a step of generating a triangular wave for each phase, a primary storage step for each phase for temporarily storing a voltage command value, and the voltage command value for comparison with the triangular wave for each phase The voltage command value stored in the primary storage step is stored in the primary storage step for each phase temporarily stored and the timing for each phase according to the phase of the triangular wave for each phase. The method of the power conversion apparatus characterized by comprising a command transfer process steps for each phase to be transferred for storage in storage step.   14. The step of generating a triangular wave for each phase, each generating a triangular wave for each phase having a phase difference, and a voltage command for the comparison independently for each phase at different timings. And a step of transferring the value. A method for controlling the power converter.   15. The method of controlling a power converter according to claim 12, further comprising a step of transferring the voltage command value for the comparison in the vicinity of a peak or valley of a triangular wave signal of each phase. .   16. The method according to claim 12, further comprising: a frequency setting step that sets the frequency of the triangular wave signal of each phase independently for each phase; and a phase adjustment step that adjusts a phase difference between the triangular wave signals of each phase. A method for controlling a power conversion apparatus, comprising:   17. The method of controlling a power converter according to claim 12, further comprising a phase difference adjustment step of adjusting the phase difference so that all of the PWM signals change at different timings.   18. The on / off ratio according to any one of claims 12 to 17, wherein the PWM signals of each phase are substantially 50% of the voltage command value at which the voltage command values of all phases are substantially zero. And the phase of each phase PWM signal is different from each other.

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