JP2013042591A - Power converter control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a phase difference among a plurality of carriers at a predetermined value by modulating the phase of the carriers with changing frequency of the carriers in generating gate pulse signals to be input into power converters.SOLUTION: In a power converter control device for inputting gate pulse signals generated by comparison of output voltage command values with carriers into a plurality of power converters for converting an AC voltage supplied from a power supply to DC voltages and converting the DC voltages to AC voltages of a desired frequency, and controlling the AC voltages output from the plurality of power converters to an AC motor, the plurality of power converters are provided for respective phases, and the phase of at least one of the plurality of carriers is modulated so as to maintain at a predetermined value a phase difference among the plurality of carriers to the plurality of power converters in phase when output voltages of the respective phases computed from the plurality of AC voltages output from the plurality of power converters of the respective phases are output to the AC motor.

Description

  The present invention relates to a power converter control device that controls an AC motor by pulse width modulation (PWM) control for a power converter that converts a DC voltage into an AC voltage having a desired frequency based on an output voltage command value. About.

  In AC motor drive using a power conversion device, AC power supplied from various commercial or non-commercial power sources is rectified by a diode inside the power conversion device, and is smoothed by a smoothing capacitor to be converted to a DC voltage. . After that, it is converted into an arbitrary AC voltage by an inverter and output to an electric motor for variable speed control. Specifically, by switching the inverter according to the PWM control based on the magnitude comparison between the output voltage command value and the carrier wave, the magnitude of the sinusoidal output voltage command value is converted into an output pulse, and the voltage is applied to the AC motor. To do. This PWM control is roughly classified into asynchronous PWM control and synchronous PWM control.

Asynchronous PWM control frequency f _c of the carrier wave, regardless of the value of the frequency f _t of the output voltage command value, is always a method of constant, universal inverters are used in the rolling mill drive inverter or the like.

On the other hand, synchronous PWM control, K times the frequency f _t always output voltage command value frequency f _c of the carrier wave: a (K 3 multiples) that method is used in electric vehicles and reactive power compensator, etc. Yes. In this case, to change the frequency f _c and the ratio of their carrier in accordance with the change in the frequency f _t of the output voltage command value.

In the asynchronous PWM control is regarded as approximately constant output voltage command value in the cycle of the carrier wave, to reduce the error in the output voltage command value and the output pulse with respect to the frequency f _t of the output voltage command value frequency f _c of the carrier wave Te is large enough (f _c / f _t: 10 or higher) is required. If the ratio of the frequency f _t of frequency f _c and the output voltage command value of the carrier is small, the output voltage command value in the cycle of the carrier wave changes greatly. For this reason, the error between the output voltage command value and the output pulse increases, problems such as a beat phenomenon occur, and pulsation (ripple) occurs in the motor output torque when the AC motor is driven.

Therefore, suppressing PWM control the beat phenomenon occurs when the ratio of the frequency f _t of frequency f _c and the output voltage command value of the carrier is small is described in Patent Document 1. Patent Document 1 describes a control method in which an average value of output voltage command values during a half cycle of a carrier wave that determines the width of an output pulse is estimated, and an output pulse is generated in accordance with the estimated value.

On the other hand, in the voltage applied to the AC motor, a sideband component f _b shown in the following formula (1) is generated by PWM control.

f _b = m · f _c + n · f _c (1)
m, n: order becomes constant frequency f _c of the carrier wave is an integer asynchronous PWM control, the sideband component f _b is changed by the basic wave frequency f _t of the output voltage command value. Furthermore, the sideband component f _b can be generated in the vicinity of the fundamental frequency f _t of the output voltage command value, the motor output torque ripple components of the low order component of several Hz~ tens Hz. When this motor output torque ripple component coincides with a low mechanical system natural frequency such as several tens of Hz, mechanical vibration is generated. The patent document 1 cannot sufficiently suppress this phenomenon.

In synchronous PWM control, K times the fundamental frequency f _t always output voltage command value frequency f _c of the carrier wave: for the (K multiple of 3), outputs the sideband component f _b shown in equation (1) It can be an integral multiple of the fundamental frequency f _t of the voltage command value. Therefore, it is possible to prevent the generation of a motor output torque ripple component having a fundamental wave frequency f _t or less of the output voltage command value. By using the synchronous PWM control, a low-order motor output torque ripple component that coincides with a mechanical natural frequency of several tens of Hz is not generated, so that the mechanical vibration described above can be prevented.

In the synchronous PWM control described above, changing the frequency f _c of the carrier wave in the AC motor driving. Therefore, as a means for suppressing the distortion of the voltage waveform applied to the AC motor at the time of switching, there has conventionally been a method of changing the carrier wave and the voltage command value synchronously at the same timing (Patent Document 2).

Japanese Patent No. 3259571 JP 2009-118599 A

15, when the division number of the control cycle in one period of the carrier wave and 4, in which said changing the frequency f _c of the carrier during operation of the AC motor as the synchronous PWM control, conventional the carrier C _A is a diagram showing the waveform of C _B. In Figure 15, have changed the value of the frequency f _c of the carrier when changing from f _c1 to f _c2, the carrier wave by the time of the timing 26 C _A, in common upper peak value Ca ₂ of C _B . Said carrier C _A, the lower the peak value of C _B is always a constant value regardless of the frequency f _c of the carrier wave.

In the case the frequency f _c of the carrier wave is f _c1 the phase difference Φ of the two carriers is 360 ° / 4 = 90 ° is a predetermined value. However, changing the frequency f _c of the carrier wave f _c2, the phase difference Φ is no longer 90 °.

Thus the phase difference Φ is a predetermined value 360 ° / L: In the case different from (L division number of the control cycle in one period of the carrier wave), the phase mismatch of the phase and the output voltage command value of the carrier C _B It becomes. According to Patent Document 1, in such a state, an output voltage error occurs in the pulse width modulation voltage, and the output voltage error becomes a beat component and pulsation (ripple) occurs in the motor output torque. When the motor output torque ripple component coincides with the mechanical natural frequency, mechanical vibration is generated.

  Further, in the method of synchronously changing the carrier wave and the voltage command value described in Patent Document 2 at the same timing, in the PWM control in the 5-level inverter as in the present invention, the phase difference Φ of the two carrier waves is the frequency of the carrier wave. Therefore, even if the above method is used, the phase difference cannot be maintained at a predetermined value, and a motor output torque ripple is generated due to an output voltage error.

  Therefore, in order to suppress the pulsation (ripple) generated in the motor output torque, which is a problem in Patent Documents 1 and 2, the problem of the present invention is to modulate the phase of the carrier wave with a change in the frequency of the carrier wave, It is an object to keep a phase difference between a plurality of carrier waves at a predetermined value.

  AC voltage command value to be output from the plurality of power converters for a plurality of power converters that convert AC voltage supplied from a power source into DC voltage and convert the DC voltage to AC voltage of a desired frequency Generating a gate pulse signal from a comparison of an output voltage command value and a carrier wave for transmitting information related to the output voltage command value, and inputting the gate pulse signal to the plurality of power converters, In the power converter controller for controlling the AC voltage to be output from the power converter to the AC motor, the plurality of power converters are provided in each phase, and the plurality of AC voltages output from the plurality of power converters in each phase When the output voltage of each phase obtained from the above is output to the AC motor, the plurality of carrier waves for the plurality of power converters in the same phase are maintained at a predetermined value so that the phase difference of the plurality of carriers is maintained at a predetermined value. Wherein the modulating at least one of the phase of the carrier out of the carrier.

  According to the present invention, when the frequency of the carrier wave is changed during the operation of the AC motor, the phase of the carrier wave can be modulated and the phase difference between the plurality of carrier waves can be maintained at a predetermined value. By matching the phases, the output voltage error of the pulse width modulation voltage can be suppressed, and the motor output torque ripple can be suppressed.

It is a figure explaining the system of this invention about the carrier wave production system of Example 1. FIG. It is a simulation result at the time of using the conventional system about the carrier wave preparation system of Example 1. FIG. It is a simulation result at the time of using this invention system about the carrier wave preparation system of Example 1. FIG. It is a figure explaining the system of this invention in case the carrier wave is a sawtooth wave about the carrier wave preparation system of Example 1. FIG. It is a figure explaining the system of this invention about the carrier wave preparation system of Example 2. FIG. It is a figure explaining the system which added the offset value to the carrier wave about the carrier wave preparation system of Example 2. FIG. It is a figure explaining the system of this invention about the carrier wave preparation system of Example 3. FIG. It is a block diagram of the serial multiple type | mold power converter device of Example 4. FIG. It is a figure explaining the system of this invention about the carrier wave preparation system of Example 4. FIG. It is a figure explaining the system of this invention about the carrier wave preparation system of Example 5. FIG. It is a figure explaining the system of this invention about the carrier wave preparation system of Example 6. FIG. It is a figure explaining the system of this invention about the carrier wave preparation system of Example 7. FIG. It is a block diagram of the 5 level power converter device which connected two single phase 3 level power converters in series. It is a block diagram of the control apparatus in FIG. It is a figure explaining a conventional system about a carrier wave preparation system. It is a figure explaining the example of the production | generation method of the gate pulse signal in a comparator. It is a figure shown about the output waveform example of the output voltage for every unit in a 5-phase inverter circuit of U phase, and the output voltage of U phase.

  A large-capacity power converter such as a multi-level power converter used in the high-voltage industrial field has N (N: natural number) single-phase power converters connected. Therefore, the control device that controls the pulse width modulation voltage applied to the AC motor based on the comparison between the output voltage command value and the carrier wave has M carrier waves (M is a natural number of 2 or more).

FIG. 13 shows a five-level power converter in which N = 2 and M = 2 and the single-phase power converter is a single-phase three-level power converter. In FIG. 13, the AC voltage supplied from the three-phase AC power supply 101 is transformed by the transformer 102, rectified by the U-phase rectifier diode 103U, the V-phase rectifier diode 103V, and the W-phase rectifier diode 103W, and U-phase smoothed. Smoothing is performed by the capacitor 104U, the V-phase smoothing capacitor 104V, and the W-phase smoothing capacitor 104W to obtain a DC voltage. Single-phase three-level power converter in U-phase five-level power converter 105V, U-phase five-level power converter 105U in which single-phase three-level power converters 201A and 201B in U-phase five-level power converter 105U are connected in series The V-phase five-level power converter 105V in which 202A and 202B are connected in series, and the W-phase five-level power converter 105W in which single-phase three-level power converters 203A and 203B in the W-phase five-level power converter 105W are connected in series. The direct current voltage is converted into alternating current having an arbitrary frequency and phase, and supplied to the alternating current motor 106 to control the alternating current motor at a variable speed. Single-phase three-level power converters 201A and 201B in the U-phase five-level power converter 105U, single-phase three-level power converters 202A and 202B in the V-phase five-level power converter 105V, and W-phase five-level power converter 105W single-phase three-level power converter 203A of the inner gate pulse signal G _{U_A} to _{203B, G U_B, G V_A,} G V_B, G W_A, G W_B the speed command value generated from the speed command generating unit 107 omega _r Calculation is performed by the control device 108 using the value of ^* .

FIG. 14 is a diagram specifically showing the configuration of the control device 108 in FIG. In FIG. 14, the multiplier 109 multiplies Pole / 2 (Pole: the number of poles) from the speed command value ω _r ^* to calculate a primary angular frequency ω ₁ . From the primary angular frequency ω ₁ , the voltage command calculator 110 calculates the d-axis voltage command value V _d ^* and the q-axis voltage command value V _q ^* . Further, the primary angular frequency ω ₁ is integrated by the integrator 111 to calculate the phase θ. Using the q-axis voltage command value V _q ^* , the d-axis voltage command value V _d ^* , and the phase θ, the output voltage command value coordinate conversion 112 outputs the output voltage command values V _U ^* , V _V ^* , V Calculate _W ^* . The carrier generator 113 calculates carrier waves C _A and C _B from the primary angular frequency ω ₁ . In the unit output voltage command converter 115U of the single-phase three-level power converters 201A and 201B from the U-phase output voltage command value V _U ^* , the output voltage command value for each U-phase single-phase three-level power converter V _{U ′} ^* is calculated, the value is multiplied by −1, and the output voltage command value −V _{U ′} ^{* obtained} by reversing the positive and negative values and the carrier waveforms of the carriers C _A and C _B are converted into a single-phase three-level power converter. The comparator 114UA connected to 201A and the comparator 114UB connected to the single-phase three-level power converter 201B compare the magnitudes to generate the PWM-modulated gate pulse signals _{GU_A} and _{GU_B} . Similarly, the output voltage command values V _{V ′} ^* and V _{W ′} ^* for each of the V-phase and W-phase single-phase three-level power converters are used as unit output voltage command converters for the single-phase three-level power converters 202A and 202B. 115V and 203A, 203B unit output voltage command converter 115W respectively calculated, multiplied by −1, and output voltage command values −V _{V ′} ^* , −V _{W ′} ^{* obtained} by reversing positive and negative, The carrier waveforms of the carrier waves C _A and C _B are PWM-modulated by comparing the carrier waveforms in the comparators 114VA, 114VB, 114WA, and 114WB connected to the single-phase three-level power converters 202A, 202B, 203A, and 203B. U-phase five-level power converters 105U, V which generate gate pulse signals G _{U_A} , G _{U_B} , G _{V_A} , G _{V_B} , G _{W_A} , G _{W_B} and connect the single-phase three-level power converters in series. The switching elements of the phase 5 level power converter 105V and the W phase 5 level power converter 105W are controlled on and off.

  FIG. 16 is a diagram illustrating how the gate pulse signal that is actually input to the single-phase three-level power converter is generated.

Here, the magnitude relationship between the carrier waveform and the output voltage command value is compared by a comparator. When the output voltage command value is low and the output voltage command value is positive with respect to the carrier waveform, FIG. at the timing of T _a, generates a gate pulse signal for switching the switching elements a and b in the left view of FIG. 17, the single-phase three-level power converter 201A or 201B is output at a voltage of 3000 V. Meanwhile, wherein the output voltage command value to the carrier wave is low and when the output voltage command value is negative, the timing of T _b in FIG. 16, by switching the switching elements c and d in the left side of FIG. 17 A gate pulse signal is generated and output to the single-phase three-level power converter 201A or 201B at a voltage of −3000V. At other timings of T _c , gate pulse signals for switching the switching elements b and c in the left diagram of FIG. 17 are generated, and the single-phase three-level power converter 201A or 201B outputs a voltage of 0V.

These switching operations are _performed by inputting the gate pulse signals G _{U_A} and G _{U_B} to the single-phase three-level power converter 201A and the single-phase three-level power converter 201B in the U phase in the left diagram of FIG. Done.

The right diagram of FIG. 17 shows an example of a waveform when the gate pulse signals G _{U_A} and G _{U_B} are inputted to the U-phase five-level power converter 105U and switched. The figure shows the configuration of the U-phase five-level power converter 105U, the output voltage waveform of the A unit, the output voltage waveform of the B unit, and the output voltage waveform of the U phase. The difference between the output voltage of the A unit and the output voltage of the B unit is taken. In each unit, what is a three-level stepped voltage value is multiplexed to obtain a five-level stepped voltage value, which is output in a waveform closer to a sine wave. ing.

  The same control is performed for the V-phase 5-level power converter 105V and the W-phase 5-level power converter 105W.

A first embodiment of the present invention is shown in FIG. FIG. 1 shows the carrier waves C _A and C _B in a five-level power converter (FIG. 11) in which N = 2, M = 2, and L = 4, and the single-phase power converter is a single-phase three-level power converter. It is the figure which showed these waveforms. Wherein the carrier wave C _A, if the value of the frequency f _c of the carrier wave is varied from f _c1 to f _c2, changes the upper peak value from Ca ₁ to Ca _2. Lower peak value regardless of the frequency f _c of the carrier wave is always constant.

On the other hand, the said carrier C _B, if the value of the frequency f _c of the carrier wave is varied from f _c1 to f _c2, a lower peak value C _ND, the upper peak value C _NU, the following equation (2), Change individually as shown in (3).

C _ND = (Ca ₁ -Ca ₂ ) / 2 (2)
C _NU = (Ca ₁ + Ca ₂ ) / 2 (3)
Said carrier C _A, C above the peak value of _B, the timing of change of the lower peak value is first up to the time of the carrier C timing 10 _{which B} is a mountain, the carrier C lower peak value C _ND of _B To change. Then by the time of the timing 11 the carrier C _A is a valley, changes the upper peak value Ca ₂ of the carrier C _A. Then by the time of the timing 12 the carrier C _B becomes a valley, changes the upper peak value C _NU of the carrier C _B. Later, when the frequency f _c of the carrier wave is changed, the same operation is repeated.

As described above, the upper peak value of the carrier C _A, and the upper peak value of the carrier C _B, by respectively changing individually the lower peak value, the carrier wave C _A, a phase difference Φ of C _B It can always be kept at a predetermined value of 360 ° / 4 = 90 °. Thereby, the output voltage error of the pulse width modulation voltage can be suppressed, and the pulsation (ripple) of the motor output torque can be suppressed.

To show the effect of the present invention, as a condition for the frequency f _c of the carrier wave changes continuously, K times (K of the fundamental wave frequency f _t always output voltage command value frequency f _c of the carrier wave: a multiple of 3 FIG. 2 and FIG. 3 show the results of simulation of fluctuations in the motor output torque of the AC motor during acceleration operation during synchronous PWM control. Compared with the conventional method of calculating the upper peak value and the lower peak value of the carrier wave (FIG. 2), the pulsation of the motor output torque can be suppressed by using the present invention (FIG. 3).

  Although the present embodiment shows a case where the carrier wave is a triangular wave, as shown in FIG. 4, even when L = 2 and the carrier wave is a sawtooth wave, the phase difference Φ between the two carrier waves is obtained in the same manner. Can always be kept at a predetermined value of 360 ° / 2 = 180 °.

Next, a difference between the second embodiment of the present invention and the first embodiment will be described. In the first embodiment, although the lower peak value of the carrier C _A was set to be always constant regardless of the frequency f _c of the carrier wave, as shown in FIG. 5, even always constant upper peak value of the carrier wave C _A Good.

Setting the upper peak value for said carrier C _A as in this example constant, the value of the frequency f _c of the carrier when changing from f _c1 to f _c2, a lower peak value from -Ca ₁ - Change to Ca ₂ .

On the other hand, the said carrier C _B, if the value of the frequency f _c of the carrier wave is varied from f _c1 to f _c2, the upper peak value C _NU, a lower peak value C _ND, the following equation (4), Change individually as shown in (5).

C _NU = (Ca ₂ −Ca ₁ ) / 2 (4)
C _ND = − (Ca ₁ + Ca ₂ ) / 2 (5)
Said carrier C _A, the upper peak value of C _B, the timing of the change of the lower peak value, firstly by the time of the carrier C timing _{13 B} is a valley, the upper peak value C _NU of the carrier C _B change. Next, the lower peak value −Ca ₂ of the carrier C _A is changed by the timing 14 when the carrier C _A becomes a peak. Next, the lower peak value C _ND of the carrier wave C _B is changed by the time point 15 when the carrier wave C _B becomes a peak. Later, when the frequency f _c of the carrier wave is changed, the same operation is repeated.

As described above, the lower the peak value of the carrier C _A, and the upper peak value of the carrier C _B, by changing the lower peak value respectively separately, the carrier C _A, the phase difference between the C _B [Phi Can always be kept at a predetermined value of 90 °. Thereby, the output voltage error of the pulse width modulation voltage can be suppressed, and the pulsation (ripple) of the motor output torque can be suppressed.

In Example 1, always upon constant regardless the lower peak value of the carrier C _A frequency f _c of the carrier, the upper peak value of the carrier C _A, the upper peak value of the carrier C _B, lower shows the case of changing the peak value individually, as in the present embodiment, the above-always constant upper peak value of the carrier wave C _a, the lower the peak value of the carrier C _a, the upper peak of the carrier wave C _B Even when the value and the lower peak value are individually changed, the same effect as in the first embodiment can be obtained.

In the embodiment 1, and this embodiment, the upper peak value of the carrier C _A, the lower the peak value, the upper peak value of the carrier C _B, is shown for the case of changing individually the lower peak value as shown in FIG. 6, even in the case of adding the offset value to the carrier C _B, it is possible to maintain two carriers of the phase difference Φ is always 90 ° is a predetermined value.

Next, a difference between the third embodiment of the present invention and the first embodiment will be described. In Example 1, always upon constant regardless the lower peak value of the carrier C _A frequency f _c of the carrier, the upper peak value of the carrier C _A, the upper peak value of the carrier C _B, lower While the peak value was changed individually, the carrier C _a, the upper peak value of C _B as shown in FIG. 7, the lower the peak value is always kept constant, the carrier C at the time of change of the frequency f _c of the carrier wave _a, it may be changed inclination of C _B.

Said carrier C _A, the timing of changing the inclination of C _B, the carrier C _A from the point of time 16 that the trough is changed to a new inclination. Later, when the frequency f _c of the carrier wave is changed, the same operation is repeated.

Thus, the carrier wave C _A, the upper peak value of C _B, the lower the peak value is always kept constant, the carrier wave C _A when the change of the frequency f _c of the carrier wave, even if you change the inclination of C _B, Since the phase difference Φ of the two carrier waves can always be kept at a predetermined value of 90 °, the same effect as in the first embodiment can be obtained.

Next, a difference between the fourth embodiment of the present invention and the first embodiment will be described. In the first embodiment, in the case of a five-level power converter in which two single-phase three-level power converters are connected in series, the phase difference Φ between the two carrier waves is always 90 °, which is a predetermined value. The present invention may be applied to the case of the serial multiplex type power converter shown in FIG. The U-phase, V-phase, and W-phase multiplex power converters are respectively indicated as a U-phase multiplex power converter 301, a V-phase multiplex power converter 302, and a W-phase multiplex power converter 303. 304 to 306 are a part of the U-phase multiplex power converter, and a plurality of similar single-phase two-level power converters are connected. 307 to 308 are single-phase two-level power converters in the V-phase multiplex power converter, and 309 to 310 are single-phase two-level power converters in the W-phase multiplex power converter. A plurality of single-phase two-level power converters are connected in the same manner as the connection configuration of the single-phase two-level power converters 304 to 306 in the power converter. For each of the single-phase two-level power converters 304 to 310, gate pulse signals G _U , G _V , and G _{W that} are PWM-modulated are output from the controller 116, and each of the single-phase two-level power converters is output. The switching elements S ₁ , S ₂ , S ₃ , S ₄ are controlled to be turned on / off.

In this embodiment, N = 2, M = 4, and L = 4, and the series multiplex power converter is a two-stage series multiplex power converter in which two single-phase two-level power converters are connected. . FIG. 9 is a diagram illustrating an example of waveforms of carrier waves C _C and C _D in the PS (Phase Shift) system in the two-stage serial multiplex type power converter. As shown in FIG. 9, to change the frequency f _c of the carrier when changing from f ₁ to f _2, the upper peak value of the carrier C _C from Ca _1/2 to Ca _2/2. Also, to change the lower peak value from -Ca _1/2 to -Ca _2/2.

On the other hand, the said carrier C _D, the upper peak value C _NU, a lower peak value C _ND, the following equation (6), be changed individually as shown in (7).

C _ND = − (Ca ₁ + Ca ₂ ) / 2 (6)
C _NU = (Ca ₂ −Ca ₁ ) / 2 (7)
Regarding the timing of changing the upper peak value and the lower peak value of the carrier waves C _C and C _D , first, the lower peak value −Ca of the carrier wave C _{C by} the time point 17 when the carrier wave C _C becomes a peak. to change the _2/2. Then, the carrier C _D is up to the time of the timing 18 of the mountain, to change the lower peak value C _ND of the carrier C _D. Then, the carrier C _C is up to the time of the timing 19 as a valley, it changes the carrier C _C of the upper peak value Ca _2/2. Then, the carrier C _D is up to the time of the timing 20 of the valley, to change the upper peak value C _NU of the carrier C _D. Later, when the frequency f _c of the carrier wave is changed, the same operation is repeated.

  As described above, in the first embodiment, the case of a five-level power conversion device in which two single-phase three-level power converters are connected in series is shown. However, as in the present embodiment, the case of a serial multiple power conversion device is shown. Since the phase difference Φ of the two carrier waves can always be kept at a predetermined value of 90 °, the same effect as in the first embodiment can be obtained.

  Next, a difference of the fifth embodiment of the present invention from the fourth embodiment will be described. In the fourth embodiment, the configuration method of the output voltage command value and the carrier wave in the two-stage serial multiplex type power converter is the PS (Phase Shift) method. However, as shown in FIG. Good.

FIG. 10 is a diagram illustrating an example of waveforms of carriers C _C1 , C _C2 , C _D1, and C _D2 in the PD (Phase Disposition) method in the two-stage serial multiplex type power converter. As shown in FIG. 10, if the frequency f _c of the carrier wave is changed from f ₁ to f _2, the upper peak value of the carrier C _C1 is changed from Ca ₁ to Ca _2. Lower peak value regardless of the value of the frequency f _c of the carrier wave is always constant.

For the carrier C _C2 , the upper peak value C ′ _NU1 is individually changed as shown in the following equation (8). Lower peak value regardless of the value of the frequency f _c of the carrier wave is always constant.

C ′ _NU1 = −Ca ₁ + Ca ₂ (8)
For the carrier C _D1 , the upper peak value C _NU2 and the lower peak value C _ND2 are individually changed as shown in the following formulas (9) and (10).

C _ND2 = (3 · Ca ₁ -Ca ₂ ) / 2 (9)
C _NU2 = (3 · Ca ₁ + Ca ₂ ) / 2 (10)
For the carrier wave C _D2 , the upper peak value C ′ _NU2 and the lower peak value C ′ _ND2 are individually changed as shown in the following equations (11) and (12).

C ′ _ND2 = − (3 · Ca ₁ + Ca ₂ ) / 2 (11)
C ′ _NU2 = − (3 · Ca ₁ −Ca ₂ ) / 2 (12)
Regarding the timing of changing the upper peak value and the lower peak value of the carrier waves C _C1 , C _C2 , C _D1 and C _D2 , first, the timing until the time point 21 at which the carrier waves C _D1 , C _D2 become peaks is the above-mentioned. lower peak value C _'ND2, lower peak value C of the carrier C _D2' of the carrier C _D1 to modify the _ND2. Then, the carrier C _C1, C _C2 is up to the time of the timing 22 as a trough, the upper peak value Ca ₂ of the carrier C _C1, changes the upper peak value C _'NU1 of the carrier C _C2. Then, the carrier C _D1, C _D2 are up to the time of the timing 23 as a trough, the upper peak value C _NU2 of the carrier C _D1, changes the upper peak value C _'NU2 of the carrier C _D2. Later, when the frequency f _c of the carrier wave is changed, the same operation is repeated.

  As described above, even when the output voltage command value and the carrier wave configuration method in the two-stage serial multiplex type power converter are the PD (Phase Disposition) method, the phase difference Φ between the two carrier waves is always set to a predetermined value. Since it can be maintained at a certain 90 °, the same effect as in the fourth embodiment can be obtained.

Next, a difference between the sixth embodiment of the present invention and the fourth embodiment will be described. In the fourth embodiment, when the output voltage command value and the carrier wave configuration method in the two-stage serial multiplex type power converter is the PS (Phase Shift) system, the upper peak value and lower side of the carrier waves C _C and C _D While the peak value was changed individually, the upper peak value of the carrier C _C, C _D as shown in FIG. 11, the lower peak value is always kept constant, the carrier C at the time of change of the frequency f _c of the carrier wave _C, may change the slope of C _D.

The timing for changing the slopes of the carrier waves C _C and C _D is changed to a new slope by the time 24 when the carrier waves C _C are peaks. Later, when the frequency f _c of the carrier wave is changed, the same operation is repeated.

Thus, when the configuration method of the output voltage command value and the carrier wave in the two-stage serial multiplex type power converter is the PS (Phase Shift) method, the carrier waves C _C , C _D as in this embodiment. the upper peak value and the lower peak value is always kept constant, the carrier wave C _C during the change of the frequency f _c of the carrier wave, when you change the inclination of C _D is also always a predetermined phase difference Φ of the two carriers Since the value can be maintained at 90 °, the same effect as in the fourth embodiment can be obtained.

Next, differences of the seventh embodiment of the present invention from the fifth embodiment will be described. In the fifth embodiment, the carrier voltages C _C1 , C _C2 , C _D1, and C _D2 when the output voltage command value and the carrier wave configuration method in the two-stage serial multiplex type power converter are PD (Phase Disposition) systems. The upper peak value and the lower peak value of the carrier waves C _C1 , C _C2 , C _D1, and C _D2 are always constant as shown in FIG. and then, the during the change of the frequency f _c of the carrier wave carrier C _C1, C _C2, C _D1 and may change the slope of the C _D2.

Regarding the timing of changing the slopes of the carrier waves C _C1 , C _C2 , C _D1, and C _D2 , the new slope is changed by the time point 25 at which the carrier waves C _C1 and C _C2 become valleys. Later, when the frequency f _c of the carrier wave is changed, the same operation is repeated.

Thus, when the configuration method of the output voltage command value and the carrier wave in the two-stage serial multiplex type power converter is the PD (Phase Disposition) method, the carrier waves C _C1 and C _C2 are used as in this embodiment. , C _D1 and the upper peak value of C _D2, and the lower peak value always constant, wherein when the change of the frequency f _c of the carrier wave carrier C _C1, C _C2, C _D1 and when changing the inclination of the C _D2 Since the phase difference Φ of the two carrier waves can always be kept at a predetermined value of 90 °, the same effect as in the fifth embodiment can be obtained.

10 to 25 Timing 101 Three-phase AC power supply 102 Transformer 103U U-phase rectifier diode 103V V-phase rectifier diode 103W W-phase rectifier diode 104U U-phase smoothing capacitor 104V V-phase smoothing capacitor 104W W-phase smoothing capacitor 105U U-phase five-level power converter 105V V-phase 5-level power converter 105W W-phase 5-level power converter 106 AC motor 107 Speed command generator 108 Control device 109 Multiplier 110 Voltage command calculator 111 Integrator 112 Output voltage command value coordinate conversion 113 Carrier wave generator 114UA , 114UB, 114VA, 114VB, 114WA, 114WB Comparator 115U, 115V, 115W Unit output voltage command converter 201A, 201B, 202A, 202B, 203A, 203B Single-phase three-level power converter 30 U-phase multi-type power converter 302 V phase multiplexing power converter 303 W-phase multi-type power converter

Claims (9)

AC voltage command value to be output from the plurality of power converters for a plurality of power converters that convert AC voltage supplied from a power source into DC voltage and convert the DC voltage to AC voltage of a desired frequency Generating a gate pulse signal from a comparison of an output voltage command value and a carrier wave for transmitting information related to the output voltage command value, and inputting the gate pulse signal to the plurality of power converters, In the power converter control device for controlling the AC voltage to be output from the power converter to the AC motor,
When the plurality of power converters are provided in each phase and the output voltage of each phase obtained from the plurality of AC voltages output from the plurality of power converters in each phase is output to the AC motor, the plurality of powers in the same phase A power converter control device that modulates the phase of at least one of the plurality of carriers so as to keep a phase difference between the plurality of carriers with respect to the converter at a predetermined value.   2. The power converter control device according to claim 1, wherein phase differences in a plurality of carrier waves are determined based on a predetermined period in which the phase of the carrier waves can be modulated.   2. The power converter control device according to claim 1, wherein the phase difference between the plurality of carrier waves is obtained by dividing 360 ° by the number of divisions of a control cycle in one cycle of the carrier wave. 3. apparatus.   4. The power converter control device according to claim 1, wherein the frequency of the carrier wave is changed to an integral multiple of the frequency of the output voltage command value. 5.   5. The power converter control device according to claim 1, wherein the power converter control device provides the gate pulse signal to a multi-level power converter including a plurality of single-phase three-level power converters. , And an AC voltage to be output from the multi-level power converter is controlled.   5. The power converter control device according to claim 1, wherein the power converter control device is configured such that the gate pulse is applied to a serial multiplex type power converter including a plurality of single-phase two-level power converters. A power converter control device, wherein a signal is input and an AC voltage output from the serial multiplex type power converter is controlled.   7. The power converter control device according to claim 1, wherein the phase is modulated by changing the slope of the carrier wave, and the phase difference between the plurality of carrier waves is maintained at a predetermined value. A power converter control device.   7. The power converter control device according to claim 1, wherein the phase is modulated by changing the amplitude of the carrier wave, and the phase difference between the plurality of carrier waves is maintained at a predetermined value. A power converter control device.   7. The power converter control device according to claim 1, wherein the phase is modulated by adding an offset value to the carrier wave, and the phase difference between the plurality of carrier waves is maintained at a predetermined value. A power converter control device.