Power converter and control method for power converter

Abstract

Provided is a power conversion device (1A) that supplies power to a multi-phase load on the basis of a first command value, which is a phase voltage command value having a sinusoidal shape, the power conversion device comprising: a multi-phase inverter circuit (3) in which legs respectively obtained by connecting in series two semiconductor switching elements having a reverse conduction function between positive and negative terminals of a DC power supply are connected in parallel in the same number as the number of phases and a terminal between the two semiconductor switching elements of each leg is connected to a respective phase of the load; a modulation voltage generator (6A) which generates a second command value configured from a fundamental wave component of the first command value and a harmonic wave component including at least one sinusoidal wave having a frequency that is an odd multiple of that of the fundamental wave component; a carrier signal generator (7A) which generates a triangle wave carrier signal such that the frequency thereof is an odd multiple of the fundamental wave component of the first command value and the central value of the triangle wave synchronizes with a phase zero of the fundamental wave component of the first command value; and a gate signal generator (8) which generates a gate signal for driving the semiconductor switching elements in accordance with the result of a comparison between the second command value and the carrier signal.

Description

[Technical Field]

[0001] This disclosure relates to a power converter that converts DC power to AC power and a method for controlling the power converter. [Background technology]

[0002] Inverters are widely used as power conversion devices that convert DC power to AC power. An inverter compares a sinusoidal modulated signal with a triangular carrier signal, switching semiconductor switching elements on and off to output a sinusoidal phase voltage. However, switching generates harmonics in the phase voltage. For example, the phase voltage has a frequency of f s The frequency of the carrier signal is f c In that case, the frequency is f c ±2f s The frequency components A and f c ±4f s This generates harmonics of frequency component B. These harmonics increase load losses and cause noise and torque pulsation.

[0003] The technology disclosed in Patent Document 1 involves superimposing harmonic components onto a sinusoidal modulation signal to disperse the ratio of frequency component A to frequency component B contained in the phase voltage. Furthermore, Patent Document 1 explains that load losses can be reduced by dispersing the ratio of frequency component A to frequency component B contained in the phase voltage. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2014-072935 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, according to the above conventional technology, when the frequencies of the noise and torque pulsation generated by the frequency component A are the same as the frequencies of the noise and torque pulsation generated by the frequency component B, there is a problem that the noise and torque pulsation cannot be reduced even if the ratio between the frequency component A and the frequency component B is dispersed.

[0006] For example, when the number of phases of the inverter is 3 and f c = 9f s , the frequencies of the frequency component A are 7f s and 11f s ; the frequencies of the frequency component B are 5f s and 13f s . Considering the frequencies of the noise and torque pulsation generated by the frequency component A, 7f s is the positive-phase component, so it becomes 6f s ; 11f s is the negative-phase component, so it becomes 12f s . Similarly, considering the frequencies of the noise and torque pulsation generated by the frequency component B, 5f s is the negative-phase component, so it becomes 6f s ; 13f s is the positive-phase component, so it becomes 12f s . That is, in the above case, even if the ratio between the frequency component A and the frequency component B is dispersed, noise and torque pulsation of the common frequency occur between the two, so these cannot be reduced.

[0007] The present disclosure has been made in view of the above, and an object thereof is to obtain a power conversion device that can effectively suppress the noise and torque pulsation generated by the switching of the inverter and reduce the loss of the load due to the harmonic components.

Means for Solving the Problems

[0008] To solve the above-mentioned problems and achieve the objective, the power converter of the present disclosure is a power converter that supplies power to a multiphase load based on a first command value which is a sinusoidal phase voltage command value, and is characterized by comprising: a multiphase inverter circuit in which two semiconductor switching elements having a reverse conduction function are connected in series between the positive and negative terminals of a DC power supply, and the same number of legs are connected in parallel as the number of phases, and the terminals between the two semiconductor switching elements in each of the multiple legs are connected to each phase of the load; a modulation voltage generator that generates a second command value which is a modulation phase voltage command value composed of a fundamental wave component of the first command value and a harmonic component which includes at least one sinusoidal wave with a frequency that is an odd multiple of the fundamental wave component; a carrier signal generator that generates a triangular wave carrier signal with a frequency that is an odd multiple of the fundamental wave component of the first command value, and such that the median value of the triangular wave is synchronized with the zero phase of the fundamental wave component of the first command value; and a gate signal generator that generates a gate signal to drive a semiconductor switching element according to the result of comparing the second command value and the carrier signal. [Effects of the Invention]

[0009] According to this disclosure, it is possible to effectively suppress noise and torque pulsation generated by inverter switching and reduce load loss due to harmonic components. [Brief explanation of the drawing]

[0010] [Figure 1] Diagram showing the configuration of the power conversion device according to Embodiment 1. [Figure 2] Figure 1 shows the configuration of the carrier signal generator. [Figure 3] Figure 2 shows the carrier signal generated by the carrier signal calculator. [Figure 4] Figure 2 shows an example of a carrier signal generated by the carrier signal calculator. [Figure 5] Figure 1 is an explanatory diagram illustrating the operation of the gate signal generator. [Figure 6] This diagram shows an example of the phase voltage output by a power converter when a sinusoidal second command value is provided to the gate signal generator. [Figure 7] Figure 1 shows the configuration of the modulation voltage generator. [Figure 8] This figure shows the waveforms of the second command value, carrier signal, and output phase voltage according to Embodiment 1. [Figure 9] This figure shows the waveforms of the phase voltage command value, carrier signal, and output phase voltage in a comparative example of Embodiment 1. [Figure 10] A diagram showing the WTHD of the power converter according to Embodiment 1. [Figure 11] Figure showing WTHD in a comparative example of Embodiment 1. [Figure 12] This figure shows the magnitude of harmonic components included in the output phase voltage of the power converter according to Embodiment 1. [Figure 13] This figure shows the magnitude of harmonic components included in the output phase voltage in a comparative example of Embodiment 1. [Figure 14] Diagram showing the configuration of the power converter according to Embodiment 2. [Figure 15] Figure 14 shows the configuration of the modulation voltage generator. [Figure 16] Diagram showing the configuration of the power converter according to Embodiment 3. [Figure 17] Figure 16 shows the configuration of the carrier signal generator. [Figure 18] Figure 16 shows the configuration of the modulation voltage generator. [Figure 19] This figure shows the waveforms of the second command value, carrier signal, and output phase voltage according to Embodiment 3. [Figure 20] This figure shows the waveforms of the phase voltage command value, carrier signal, and output phase voltage in a comparative example of Embodiment 3. [Figure 21] A diagram showing the WTHD of the power converter according to Embodiment 3. [Figure 22] Figure showing WTHD in a comparative example of Embodiment 3. [Figure 23] This figure shows the magnitude of harmonic components included in the output phase voltage of the power converter according to Embodiment 3. [Figure 24] This figure shows the magnitude of harmonic components included in the output phase voltage in the comparative example of Embodiment 3. [Figure 25] This diagram shows an example configuration of a power converter using dedicated hardware. [Figure 26] This diagram shows an example configuration of a power converter using a processor and memory device. [Modes for carrying out the invention]

[0011] The power converter and control method for the power converter according to embodiments of this disclosure will be described in detail below with reference to the drawings.

[0012] Embodiment 1. Figure 1 shows the configuration of the power converter 1A according to Embodiment 1. The power converter 1A includes a multiphase inverter circuit 3 connected to a DC power supply 2 and a load motor 4, a modulation voltage generator 6A, a carrier signal generator 7A, and a gate signal generator 8.

[0013] The multiphase inverter circuit 3 converts the DC power from the DC power supply 2 into multiphase AC power and outputs it to the motor 4. Here, the multiphase inverter circuit 3 has 3 phases, and each phase is designated as the u-phase, v-phase, and w-phase. The multiphase inverter circuit 3 has a configuration in which two semiconductor switching elements Q with reverse conduction function are connected in series, and these legs 31 are connected in parallel, one for each phase. Since the multiphase inverter circuit 3 has 3 phases, it has 6 semiconductor switching elements Q, and as shown in Figure 1, each of the 6 semiconductor switching elements Q is a semiconductor switching element Q up Q un Q vp Q vn Q wp Q wn It is referred to as such. Also, the positive semiconductor switching element Q corresponding to the u phase. up and the negative semiconductor switching element Q un The series connection of these elements is called Leg 31u, and the positive semiconductor switching element Q corresponds to the v phase. vp and the negative semiconductor switching element Q vnA series connection of these is called Leg31V, and the positive semiconductor switching element Q corresponds to the W phase. wp and the negative semiconductor switching element Q wn A series connection of these elements is called Leg 31w. The intermediate terminals of each Leg 31 are connected to the respective phases of the motor 4. Here, each semiconductor switching element Q is composed of an IGBT (Insulated Gate Bipolar Transistor) and an antiparallel diode. If a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), RC (Reverse Conducting)-IGBT, etc. are used instead of an IGBT, the antiparallel diode may be omitted.

[0014] The motor controller 5 determines a first command value v, which is a sinusoidal phase voltage command value, from the torque command value of the motor 4, as the voltage to be supplied to the motor 4. u * ,v v * ,v w * The motor controller 5 calculates the first command value v. u * ,v v * ,v w * This is output to the modulation voltage generator 6A and the carrier signal generator 7A, respectively.

[0015] The modulation voltage generator 6A receives the first command value v u * ,v v * ,v w * Based on this, the second command value m is the phase voltage command value for modulation. u ,m v ,m w The modulated voltage generator 6A generates the second command value m u ,m v ,m w The first command value v is output to the gate signal generator 8. u* , v v * , v w * Based on this, a triangular carrier signal c is generated. The carrier signal generator 7A outputs the generated carrier signal c to the gate signal generator 8. The gate signal generator 8 compares the magnitude of the second command value m u , m v , m w with the magnitude of the carrier signal c to control the on and off of the semiconductor switching element Q of the multiphase inverter circuit 3, and generates a gate signal g up , g un , g vp , g vn , g wp , g wn Each of the gate signals g up , g un , g vp , g vn , g wp , g wn corresponds to each of the semiconductor switching elements Q up , Q un , Q vp , Q vn , Q wp , Q wn and turns on or off the corresponding semiconductor switching element Q. When not distinguishing each of the gate signals g up , g un , g vp , g vn , g wp , g wn , they are simply referred to as the gate signal g.

[0016] FIG. 2 is a diagram showing the configuration of the carrier signal generator 7A shown in FIG. 1. The carrier signal generator 7A includes a three-phase to two-phase converter 701, a phase calculator 702, and a carrier signal calculator 703A.

[0017] The three-phase to two-phase converter 701 converts the first command value v on the three-phase coordinates u * , v v * , v w * into the first command value v on the two-phase coordinatesα * , v β * is converted into a two-phase signal. The three-phase to two-phase converter 701 can perform the three-phase to two-phase conversion using, for example, the following mathematical formula (1).

[0018]

Number

[0019] The phase calculator 702 calculates the fundamental wave phase θ of the u-phase of the first command value v on the two-phase coordinates α * , v β * . Specifically, first, an arctangent operation is performed on the first command value v on the two-phase coordinates v α * , v β * to obtain the phase of v α * . This phase is the same as the phase of v u * . However, since the phase of v α * is obtained by performing an arctangent operation on the first command value v on the two-phase coordinates β , v * is based on the cos signal reference, the phase of the sin signal reference can be obtained by subtracting "π / 2" from this phase. α * u Note that here, the first command value v * v * , v w and the first command value v [[ID=5" * , v α * , v β * and the first command value v u * , v v * are waveforms with sufficiently few harmonic components and are the same as the fundamental wave components. It is described on the premise that the response of the motor controller 5 is fast and the first command value v w * , v α* ,v w * and the first command value v α * ,v β * If the signal contains many harmonic components, the fundamental wave component can be extracted by passing it through a low-pass filter, for example.

[0021] The carrier signal calculator 703A first calculates a carrier signal c whose frequency is an odd number Kc multiple of the fundamental wave component. Specifically, it generates the phase of the carrier signal by multiplying the fundamental wave phase θv by an odd number Kc. The carrier signal calculator 703A then generates a triangular wave carrier signal c as shown in Figure 3. Figure 3 is a diagram representing the carrier signal generated by the carrier signal calculator 703A shown in Figure 2. Furthermore, the carrier signal calculator 703A performs phase-synchronization control to correct the phase of the carrier signal c so that the median value of the triangular wave coincides with the phase 0° of the phase voltage command value. In the example shown in Figure 3, the median value of the triangular wave is zero. The carrier signal calculator 703A outputs the carrier signal c, after phase-synchronization control, to the gate signal generator 8.

[0022] In this embodiment, the odd number Kc is set to 9, and the phase of the carrier signal c is synchronized to the phase of the phase voltage command value at 0°, with a phase of 270°. At this time, the carrier signal will be as shown in Figure 4. Figure 4 is a diagram showing an example of the carrier signal c generated by the carrier signal calculator 703A shown in Figure 2. In this embodiment, the carrier signal c is synchronized to the phase of the u-phase voltage, and a common carrier signal c is used for all three phases. For this reason, the odd number Kc that determines the frequency of the carrier signal c is set to a multiple of the number of phases, 3.

[0023] Returning to the explanation of Figure 1, the gate signal generator 8 receives the second command value m, which is the modulation phase voltage command value output by the modulation voltage generator 6A. u ,m v ,m w By comparing each of these with the carrier signal c, the semiconductor switching element Q of the multiphase inverter circuit 3 is determined. up Q un Q vp Qvn Q wp Q wn Gate signals g control the on and off states of each. up ,g un ,g vp ,g vn ,g wp ,g wn Generates a gate signal g. up ,g un ,g vp ,g vn ,g wp ,g wn Each of these can take a high "H" or low "L" value. When the value of the gate signal g is "H", the semiconductor switching element Q corresponding to that gate signal g is controlled to be ON, and when the value of the gate signal g is "L", the semiconductor switching element Q corresponding to that gate signal g is controlled to be OFF.

[0024] Figure 5 is an explanatory diagram of the operation of the gate signal generator 8 shown in Figure 1. Figure 5 shows the u-phase component. The gate signal generator 8 receives the second command value m u The gate signal g is obtained by comparing it with the carrier signal c. up and g un This generates the second command value m. Specifically, here, the second command value m u When the gate signal g is greater than the carrier signal c, up Set the value of to "H", and the gate signal g un Let the value of be "L", and the second command value m u When the gate signal g is smaller than the carrier signal c, up The value of is "L", gate signal g un Let the value be "H". Gate signal g up and g un They are complementary to each other. That is, gate signal g up When it is "H", the gate signal g un This is "L", and the gate signal g up When it is "L", the gate signal g un This becomes "H". Gate signal g up When it is "H", the positive semiconductor switching element Q up When it turns on, the output phase voltage v u is vdc / 2, which is the gate signal g un When it is "H", the negative semiconductor switching element Q un When it turns on, the output voltage v u -v dc The output phase voltage v is / 2. u When averaged over the period of the carrier signal c, the first command value v is obtained. u * A phase voltage is obtained according to this.

[0025] Here, by examining the carrier signal c generated by the carrier signal generator 7A described above and the harmonic components expected to be generated when using the gate signal generator 8, we can determine the second command value m generated by the modulation voltage generator 6A. u ,m v ,m w Let's consider this. Figure 6 shows the sinusoidal second command value m u This figure shows an example of the phase voltage output by the power converter 1A when the gate signal generator 8 is supplied with the carrier signal c and the gate signal generator 8. In Figure 6, the carrier signal c and the gate signal generator 8 are used to generate a second command value m, which is a phase voltage command value for sinusoidal modulation. u ,m v ,m w The waveform of the phase voltage output when the multiphase inverter circuit 3 is operated by generating a gate signal g from the above is shown for the u-phase component. The upper part of Figure 6 shows the sinusoidal second command value m. u The triangular wave carrier signal c is shown, and at the bottom of Figure 6 is the sinusoidal second command value m. u And the output phase voltage v is output based on the triangular wave carrier signal c. u This is shown. The output phase voltage v output by power converter 1A uThe waveform, based on the concept of Fourier series expansion, can be represented as the sum of sinusoidal and cosine components of various orders. Here, since the phase voltage is positively and negatively symmetrical from phase 0° to 180° and from phase 180° to 360°, even-order harmonic components are first removed. Next, the phase voltage is inverted symmetrically from phase 0° to 90° and from phase 90° to 180°, and cosine components are also removed. Therefore, when using the carrier signal c of this embodiment, the harmonic components of the phase voltage consist only of odd-order sinusoidal components. Furthermore, based on this result, the first command value v u * ,v v * ,v w * or the second command value m u ,m v ,m w When optimizing the phase voltage waveform by superimposing harmonic components, the first command value v u * ,v v * ,v w * or the second command value m u ,m v ,m w We only need to superimpose odd-order sinusoidal components onto it.

[0026] Figure 7 shows the configuration of the modulation voltage generator 6A shown in Figure 1. The modulation voltage generator 6A includes a three-phase two-phase converter 601, an amplitude calculator 602, a phase calculator 603, a waveform calculator 604A, and a waveform memory device 605.

[0027] The three-phase two-phase converter 601 processes in the same way as the three-phase two-phase converter 701 to obtain a first command value v, which is a sinusoidal phase voltage command value on the three-phase coordinate system. u * ,v v * ,v w * The first command value v on the two-phase coordinate system α * ,v β * It converts from three phase to two phase. The three-phase two-phase converter 601 converts the first command value v on the two-phase coordinate system. α* ,v β * This is output to the amplitude calculator 602 and the phase calculator 603, respectively.

[0028] The amplitude calculator 602 first calculates the first command value v on the two-phase coordinate system. α * ,v β * From the first command value v α * ,v β * amplitude v php The following calculation is performed. For example, the amplitude calculator 602 uses the following formula (2) to calculate the first command value v α * ,v β * amplitude v php It is possible to perform calculations on this.

[0029]

number

[0030] Next, the amplitude calculator 602 calculates the first command value v as shown in the following equation (3). α * ,v β * amplitude v php Divide this by half the DC voltage to obtain the second command value m, which is the modulation voltage command value. u ,m v ,m w The amplitude is converted to M. The amplitude calculator 602 outputs the calculated amplitude M to the waveform calculator 604A.

[0031]

number

[0032] The phase calculator 603 performs the same processing as the phase calculator 702 to obtain the first command value v on the two-phase coordinate system. α * ,v β * The fundamental wave phase θ of the u-phasev The phase calculator 603 calculates the fundamental wave phase θ, which is the result of the calculation. v The output is sent to the waveform calculator 604A.

[0033] The waveform calculator 604A calculates the amplitude M and the fundamental wave phase θ of the u-phase. v Using this, the second command value m u ,m v ,m w The waveform is calculated. Specifically, the first command value v u * ,v v * ,v w * The second command value m corresponds to a quarter period from the phase 0° to 90° of the fundamental wave. u ,m v ,m w The waveform is pre-stored in the waveform memory device 605, and the second command value m is used with the stored waveform. u ,m v ,m w This generates the following. Here, the waveform calculator 604A calculates the phase voltage, i.e., the second command value m u ,m v ,m w By utilizing the fact that the waveforms are positively and negatively symmetrical from phase 0° to 180° and from phase 180° to 360°, and that they are invertedly symmetrical from phase 0° to 90° and from phase 90° to 180°, the waveform for one cycle of the fundamental wave is reproduced from the waveform corresponding to one-quarter of the fundamental wave's period. Note that since the waveforms of the three-phase modulation phase voltage command values ​​are shifted in phase by 120° from each other, the waveform calculator 604A calculates the fundamental wave phase θ of the u-phase. v After generating the u-phase waveform using this method, the phase is shifted to obtain the second command value m for all three phases. u ,m v ,m w It can generate [this].

[0034] The second command value m to be stored in the waveform memory device 605 u ,m v ,m wThe waveform is generated such that, when the carrier signal c generated by the carrier signal generator 7A in this embodiment is used, the fundamental wave component of the phase voltage matches the command value and the harmonic components are optimized. Here, in this embodiment, the first command value v u * ,v v * ,v w * By a simple method of superimposing only odd-order sinusoidal components, which are harmonic components, onto the fundamental wave component, the optimal second command value m is determined. u ,m v ,m w It is possible to find this.

[0035] As a method for superimposing harmonic components onto the phase voltage command value, International Publication No. 2019 / 016901 discloses a method for superimposing third harmonics onto a three-phase inverter circuit. In this method, by superimposing harmonics whose frequencies are integer multiples of the number of phases, it is possible to supply a larger AC voltage to the load by effectively utilizing the DC voltage without changing the output voltage on the load side of the multiphase inverter circuit 3. In contrast, in this embodiment, harmonic components whose frequencies are not integer multiples of the number of phases, i.e., sine waves, are also superimposed onto the phase voltage command value. This makes it possible to optimize the frequency distribution of harmonic components generated by the switching of the multiphase inverter circuit 3.

[0036] Furthermore, in this embodiment, the second command value m u ,m v ,m w This value is kept constant during the carrier half-cycle, which is the period during which the carrier signal c changes from its minimum value to its maximum value or from its maximum value to its minimum value. In this embodiment, since an odd number Kc is set to 9, the quarter-period of the fundamental wave stored in the waveform memory device 605 corresponds to 4.5 times the carrier half-period. However, in order to maintain the symmetry of the phase voltage waveform, the second command value m is set during the first 0.5 periods. u ,m v ,m wThis is set to zero. Therefore, in this embodiment, it is only necessary to optimize and store four values ​​corresponding to four intervals of the carrier half-cycle, making optimization easy.

[0037] Note that here, the second command value m for one phase is u ,m v ,m w While it was decided to save the waveform for one-quarter of a period of the fundamental wave, the storage period can be reduced when storing waveforms for multiple phases. When there are three phases, during the period when the phase of the u-phase voltage is from 0° to 30°, the phase of the v-phase voltage is from -120° to -90°, i.e., from 240° to 270°. Considering the symmetry of the waveform, this waveform is the same as the waveform during the period from 60° to 90° of the u-phase voltage, but inverted in the time direction, i.e., in the phase direction. Next, during the period when the phase of the u-phase voltage is from 0° to 30°, the phase of the w-phase voltage is from -240° to -210°, i.e., from 120° to 150°. Considering the symmetry of the waveform, this waveform is the same as the waveform during the period from 30° to 60° of the u-phase voltage, but inverted in the time direction, i.e., in the phase direction. Therefore, the second command value m for the three phases... u ,m v ,m w When storing waveforms, if you store the waveform for the period from 0° to 30° of phase, you can reproduce the waveform for the period from 0° to 90°. In other words, the second command value m for multiphase u ,m v ,m w When storing the waveform, you only need to store the waveform for a period obtained by dividing the 90° period (one-quarter of the fundamental wave period) by the number of phases.

[0038] In this embodiment, the optimization of the harmonic components of the phase voltage is performed using the objective function f, which is expressed by the following equation (4). obj Perform the action to minimize the value.

[0039]

number

[0040] Here, the harmonic components are optimized so that the root of the sum of the squares of the values ​​obtained by dividing the nth harmonic voltage vn by its order n, i.e., the effective current of the load, is minimized. Here, n = 6i ± 1. However, certain frequency components, in this case the 5th and 7th harmonic components, are assumed to excite mechanical resonance in the load and cause large noise and torque pulsations, and these are preferentially reduced by increasing the weight of these order components. That is, the weight k in equation (4) n As shown in the following equation (5), the value is greater when n is 5 and when n is 7 than when n is not 5 or 7. This allows for reduced load loss while suppressing noise and torque pulsation.

[0041]

number

[0042] In this embodiment, the number of phases in the multiphase inverter circuit 3 and motor 4 is set to 3, and the waveforms of the three phases are shifted in phase by 120° from each other, so no harmonic components that are multiples of 3 are generated. Furthermore, since the voltage waveforms of each phase are positively and negatively symmetrical between phases 0° to 180° and phases 180° to 360°, no harmonic components that are multiples of 2 are generated. In addition, in the optimization process, harmonic components up to the 50th order are considered.

[0043] Figure 8 shows the second command value m according to Embodiment 1. u ,m v ,m w , carrier signal c and output phase voltage v u This figure shows the waveform. Figure 8 shows the case where the amplitude M = 0.8. The second command value m u ,m v ,m w The first command value v u * ,v v * ,v w *It consists of a fundamental wave component and harmonic components including odd-order sinusoidal components. Here, the harmonic components include sinusoidal components whose frequencies are not integer multiples of the number of phases. Specifically, the second command value m u ,m v ,m w The signal contains superimposed sine wave components with frequencies 3, 5, 7, 11, 13, 15, 17, 19, and 21 times that of the fundamental wave component. Note that while only the sine wave component with a frequency 21 times that of the fundamental wave component is listed here, the second command value m u ,m v ,m w Furthermore, a sinusoidal component with an even higher frequency is superimposed. The output phase voltage v of the u-phase. u It exhibits positive and negative symmetry between phases 0° to 180° and phases 180° to 360°, and inversion symmetry between phases 0° to 90° and phases 90° to 180°. Also, the second command value m u ,m v ,m w This value remains constant over the carrier half-cycle.

[0044] To explain the effects of the power converter 1A according to this embodiment, a comparative example using general carrier-synchronous PWM (Pulse Width Modulation) will be described. Figure 9 shows the phase voltage command value, carrier signal c, and output phase voltage v in the comparative example of Embodiment 1. u This figure shows the waveform. The difference from the example of Embodiment 1 shown in Figure 8 is that harmonic components are not superimposed on the phase voltage command value. The carrier signal c is the same as the example shown in Figure 8.

[0045] Here, the effective current value of the load, motor 4, is evaluated using WTHD, which is expressed by the following formula (6).

[0046]

number

[0047] The numerator of equation (6) is the square root of the sum of the squares of the values ​​obtained by dividing the nth harmonic voltage vn by its order n, which is equivalent to the effective current of the load. By dividing this effective current by the amplitude v1 of the fundamental wave voltage in the denominator, WTHD is obtained as the value equivalent to the current distortion rate.

[0048] Here, we compare the WTHD values ​​of the power converter 1A according to this embodiment with those of a comparative example. Figure 10 shows the WTHD of the power converter 1A according to Embodiment 1. Figure 11 shows the WTHD of the comparative example of Embodiment 1. Comparing Figure 10 and Figure 11, it can be confirmed that the WTHD can be significantly reduced, particularly in the region where the amplitude M of the modulated voltage is large, thereby reducing the effective value of the load current, i.e., the loss.

[0049] Furthermore, the harmonic components included in the output phase voltage are compared between the power converter 1A according to this embodiment and a comparative example. Figure 12 shows the magnitude of the harmonic components included in the output phase voltage of the power converter 1A according to Embodiment 1. Figure 13 shows the magnitude of the harmonic components included in the output phase voltage of the comparative example of Embodiment 1. In Figures 12 and 13, the horizontal axis represents the amplitude M, and the vertical axis represents the frequency of the harmonics, expressed as the order relative to the fundamental wave. Also, in Figures 12 and 13, the magnitude of the harmonic component is equal to the amplitude v of the output phase voltage. ph The value obtained by dividing by half the DC voltage is shown by the shade of color. By comparing Figures 12 and 13, it can be seen that the power converter 1A according to this embodiment is able to significantly reduce specific frequency components, in this case the 5th and 7th harmonic components, which are assumed to excite mechanical resonance in the load and cause large noise and torque pulsation. The amplitudes of the 5th and 7th harmonic components are less than a few percent of the amplitude M of the fundamental wave component, confirming that they have been almost completely eliminated.

[0050] As described above, the power converter 1A according to Embodiment 1 has a first command value v which is a sinusoidal phase voltage command value. u * ,v v * ,vw * Based on this, power is supplied to the motor 4, which is a multiphase load. The power converter 1A consists of a multiphase inverter circuit 3 in which two semiconductor switching elements Q, which have a reverse conduction function, are connected in series between the positive and negative terminals of the DC power supply 2, and the same number of legs 31 are connected in parallel as the number of phases, and the terminals between the two semiconductor switching elements Q in each of the multiple legs 31 are connected to each phase of the motor 4, which is the load, and a first command value v u * ,v v * ,v w * The second command value m is a modulation phase voltage command value composed of the fundamental wave component and a harmonic component that includes at least one sine wave with a frequency that is an odd multiple of the fundamental wave component. u ,m v ,m w A modulation voltage generator 6A generates a triangular wave carrier signal c, and a first command value v u * ,v v * ,v w * The frequency of the fundamental wave component is an odd multiple, and the median of the triangular wave is the first command value v u * ,v v * ,v w * A carrier signal generator 7A generates a signal synchronized with the phase zero of the fundamental wave component, and a second command value m u ,m v ,m w The system includes a gate signal generator 8 that generates gate signals g to drive each of the multiple semiconductor switching elements Q of the multiphase inverter circuit 3 according to the result of comparing the magnitude relationship between the signal and the carrier signal c.

[0051] The carrier signal c of the triangular wave corresponds to the first command value v u * ,v v * ,v w * The frequency of the fundamental wave component is an odd multiple, and the median of the triangular wave is the first command value v u* , v v * , v w * By having the characteristic of synchronizing with the phase zero of the fundamental wave component of this, when driving the multiphase inverter circuit 3 with the gate signal g generated using this carrier signal c, the generated phase voltage becomes positive and negative symmetric between phase 0° to 180° and phase 180° to 360°, and becomes inversion symmetric between phase 0° to 90° and phase 90° to 180°. Therefore, the phase voltage does not contain even harmonic components or cosine wave components, and the harmonic components contained in the phase voltage are only odd-order sine wave components. Thus, the second command value m u , m v , m w is composed of the fundamental wave component of the first command value v u * , v v * , v w * and at least one harmonic component including a sine wave whose frequency is an odd multiple of the fundamental wave component, making it possible to suppress the harmonic components contained in the output phase voltage. The frequency distribution of the harmonics generated by the switching of the multiphase inverter circuit 3 can be optimized with a relatively simple configuration. Thereby, the frequency components that generate load noise and torque ripple can be effectively suppressed, and at the same time, the load loss due to harmonic components can be reduced.

[0052] Note that the harmonic components contained in the second command value m u , m v , m w can include at least one sine wave whose frequency is an odd multiple of the fundamental wave component of the first command value v u * , v v * , v w * and is not an integer multiple of the number of phases of the multiphase inverter circuit 3.

[0053] Also, the modulation voltage generator 6A is the first command value v u * , v v* , v w * The second command value m corresponding to a quarter cycle of the fundamental wave component of u , m v , m w is stored in the waveform memory device 605, and the second command value m is generated using the waveform memory device 605 u , m v , m w As described above, the carrier signal c has a frequency that is an odd multiple of the fundamental wave component of the first command value v u * , v v * , v w * and the center value of the triangular wave is the first command value v. By synchronizing with the phase zero of the fundamental wave component of u * , v v * , v w * the generated phase voltage is positive-negative symmetric between phase 0° to 180° and between phase 180° to 360°, and is inversion symmetric between phase 0° to 90° and between phase 90° to 180°. Therefore, as long as the second command value m corresponding to a quarter cycle of the fundamental wave component is stored u , m v , m w the second command value m for one cycle can be generated by utilizing the above characteristics u , m v , m w can be generated

[0054] The multiple of the frequency of the fundamental wave component of the carrier signal c with respect to the frequency can be an odd number and an integer multiple of the number of phases of the multiphase inverter circuit 3. Thereby, the carrier signal c can be synchronized with the phase of the phase voltage of any phase, and a common carrier signal c can be used in multiple phases

[0055] In the carrier half cycle, which is the period during which the carrier signal c changes from the minimum value to the maximum value or the period during which the carrier signal c changes from the maximum value to the minimum value, the second command value m u , m v,m w This is kept at a constant value. This reduces the number of values ​​stored in the waveform memory device 605, thereby suppressing the required storage capacity. Specifically, in Embodiment 1, Kc = 9, one-quarter of the period of the fundamental wave component corresponds to 4.5 times the carrier half-period, and in the first 0.5 period, the second command value m u ,m v ,m w To make it zero, four second command values ​​m u ,m v ,m w Only the necessary parts need to be optimized and stored, making optimization easy.

[0056] Furthermore, as explained above using formula (4), in power converter 1A, the second command value m u ,m v ,m w The second command value m is set such that the effective current of the load is lower compared to when no harmonic components are present. u ,m v ,m w This is optimized. Also, by using the weighting coefficient shown in equation (5), the second command value m u ,m v ,m w Compared to a case where no harmonic components are present, the second command value m is set such that the amplitude of predetermined frequency components, such as the 5th and 7th harmonic components, is lower. u ,m v ,m w It has been optimized.

[0057] Embodiment 2. Figure 14 shows the configuration of power converter 1B according to Embodiment 2. Power converter 1B includes a multiphase inverter circuit 3, a modulation voltage generator 6B, a carrier signal generator 7A, and a gate signal generator 8. Power converter 1B has a modulation voltage generator 6B instead of the modulation voltage generator 6A of power converter 1A according to Embodiment 1. Below, the parts common to power converter 1A according to Embodiment 1 will be omitted from the explanation, and the parts that differ from power converter 1A will be mainly explained.

[0058] In phase-synchronous control, where the carrier signal c is synchronized with the phase voltage command value of the load, if the phase or frequency of the voltage to be supplied to the load changes transiently, an identification time is required to synchronize the carrier signal c with the phase voltage command value. In Embodiment 1, a second command value m is determined based on the phase of the carrier signal c. u ,m v ,m w To generate the first command value v, the phase of the carrier signal c is set to the first command value v u * ,v v * ,v w * While not perfectly synchronized, the second command value m u ,m v ,m w In other words, the phase voltage of the load will not be synchronized with the first command value. Therefore, the modulation voltage generator 6B will not synchronize with the first command value v u * ,v v * ,v w * Even if the phase or frequency of changes transiently, the first command value v u * ,v v * ,v w * The second command value m synchronized with this u ,m v ,m w It has the capability to generate them quickly.

[0059] Figure 15 shows the configuration of the modulation voltage generator 6B shown in Figure 14. The modulation voltage generator 6B includes a three-phase two-phase converter 601, an amplitude calculator 602, a phase calculator 603, a waveform calculator 604B, and an order amplitude memory device 606B.

[0060] The modulation voltage generator 6B has a waveform calculator 604B instead of the waveform calculator 604A of the modulation voltage generator 6A according to Embodiment 1, and has an order amplitude storage device 606B instead of the waveform storage device 605.

[0061] The order amplitude memory device 606B contains an optimized second command value m u ,m v ,m w The following information is stored in advance. Specifically, the order amplitude memory device 606B stores the second command value m for the amplitude M. u ,m v ,m w The amplitude m1 of the fundamental wave component, the amplitude of the sine wave to be included as a harmonic component, and the multiple of the frequency of the sine wave to be included as a harmonic component relative to the fundamental wave component are stored. Here, the harmonic components are set to frequencies 3, 5, and 7 times that of the fundamental wave component, with amplitudes m3, m5, and m7, respectively. Note that m1, m3, m5, and m7 are stored in correspondence to the respective values ​​of amplitude M, with m1(M) being the amplitude of the fundamental wave component relative to amplitude M, and m3(M), m5(M), and m7(M) being the amplitudes of the sine wave relative to amplitude M. Here, the harmonic component when the phase of the sine wave is 180° can be reproduced by setting the amplitude to a negative value.

[0062] In Embodiment 2, the second command value m, as shown in Figure 8, is optimized in the same manner as in Embodiment 1. u ,m v ,m w This is utilized. In Embodiment 1, in order to reproduce the waveform for one-quarter of a period of the fundamental wave component, four voltage command values ​​for four sections of the carrier half-period were stored. Since the degrees of freedom are 4, the original optimal waveform can be reproduced by using the fundamental wave component and three harmonic components of different frequencies.

[0063] The waveform calculator 604B calculates the second command value m for the amplitude M. u ,m v ,m w The waveform is calculated. For example, the second command value m of the u phase with respect to the amplitude M. u (M) can be calculated using the following formula (7).

[0064]

number

[0065] Furthermore, the second command value of the three phase is m u ,m v ,m w Since the waveforms are those in which the phase of the fundamental wave components is shifted by 120° relative to each other, the second command value m for the three phases is obtained using the fundamental wave phase θv of the u phase. u ,m v ,m w It can generate [this].

[0066] As explained above, according to the power converter 1B of Embodiment 2, the second command value m of Embodiment 1 u ,m v ,m w Since this is reproduced by function approximation, firstly, the same effects as in Embodiment 1 can be obtained. Specifically, similar to Embodiment 1, the effective value of the load current, i.e., the loss, can be reduced. In addition, it becomes possible to reduce, and almost completely eliminate, certain frequency components, such as the 5th and 7th harmonic components, which are assumed to excite mechanical resonance in the load and cause large noise and torque pulsation.

[0067] Furthermore, in the power converter 1B according to Embodiment 2, the modulation voltage generator 6B receives the first command value v u * ,v v * ,v w * The amplitude m1 of the fundamental wave component, the amplitude of the sine wave included in the harmonic component, and the multiple of the frequency of the sine wave included in the harmonic component relative to the fundamental wave component are stored in the order amplitude memory device 606B, which is a memory device, and the second command value m u ,m v ,m w This generates the first command value v u * ,v v * ,v w * Even when the phase and frequency of the carrier signal c are transiently changing and the phase-synchronized control of the carrier signal c cannot keep up, the first command value v u * ,v v* ,v w * The voltage supplied to the load can be supplied according to this. Therefore, it becomes possible to control the voltage supplied to the load with high precision and high response.

[0068] The carrier signal generator 7A generates a carrier signal c with a frequency 9 times that of the fundamental wave component, and the second command value m u ,m v ,m w It includes three sine waves of different frequencies as harmonic components. For example, the second command value m u ,m v ,m w The fundamental wave component may include sine waves with frequencies 3, 5, and 7 times that of the fundamental wave component as harmonic components.

[0069] As described above, the power conversion device 1B according to Embodiment 2 can achieve remarkable effects in addition to the effects of Embodiment 1, such as being able to control the voltage supplied to the load with high precision and high response.

[0070] Embodiment 3. Figure 16 shows the configuration of power converter 1C according to Embodiment 3. Power converter 1C includes a multiphase inverter circuit 3, a modulation voltage generator 6C, a carrier signal generator 7B, and a gate signal generator 8. Power converter 1C has a modulation voltage generator 6C instead of the modulation voltage generator 6A of power converter 1A according to Embodiment 1, and a carrier signal generator 7B instead of the carrier signal generator 7A. Below, the parts common to power converter 1A according to Embodiment 1 will be omitted from the explanation, and the parts that differ from power converter 1A will be mainly explained.

[0071] Figure 17 shows the configuration of the carrier signal generator 7B shown in Figure 16. The carrier signal generator 7B includes a three-phase two-phase converter 701, a phase calculator 702, and a carrier signal calculator 703B. The carrier signal generator 7B has a carrier signal calculator 703B instead of the carrier signal calculator 703A of the carrier signal generator 7A according to Embodiment 1.

[0072] The function of the carrier signal calculator 703B is basically the same as that of the carrier signal calculator 703A. The difference from the carrier signal calculator 703A is that the carrier signal calculator 703B sets the odd number Kc to 15 and generates a carrier signal c whose frequency is 15 times that of the fundamental wave component. Regarding the phase synchronization control, the carrier signal generator 7B is the same as the carrier signal generator 7A in synchronizing the median value of the triangular wave to the phase 0° of the first command values v u * ,v v * ,v w * , specifically, synchronizing the phase 270° of the carrier signal c. Also, in the third embodiment, similar to the first embodiment, the carrier signal c is synchronized with the phase of the u-phase voltage, and the common carrier signal c is used for the three phases. Therefore, the odd number Kc that determines the frequency of the carrier signal c is set to a multiple of the number of phases 3.

[0073] FIG. 18 is a diagram showing the configuration of the modulation voltage generator 6C shown in FIG. 16. The modulation voltage generator 6C includes a three-phase to two-phase converter 601, an amplitude calculator 602, a phase calculator 603, a waveform calculator 604C, and a harmonic amplitude storage device 606C.

[0074] <​​​​​​​​​​​​​​​​The amplitude m1 of the fundamental wave component, the amplitude of the sine wave to be included as a harmonic component, and the multiple of the frequency of the sine wave to be included as a harmonic component relative to the fundamental wave component are stored. Here, the harmonic components are set to six frequencies: 3, 5, 7, 9, 11, and 13 times the fundamental wave component, with amplitudes of m3, m5, m7, m9, and m 11 , m 13 Let's assume that m1, m3, m5, m7, m9, m 11 , m 13 These values ​​are stored in correspondence to each of the amplitude M values, with m1(M) being the amplitude of the fundamental wave component for amplitude M, and m3(M), m5(M), m7(M), m9(M), and m being the amplitudes of the sine wave for amplitude M. 11 (M), m 13 Let (M). Here, the harmonic components when the phase of the sine wave is 180° can be reproduced by setting the amplitude to a negative value.

[0076] Second command value m u ,m v ,m w This value is kept constant during the carrier half-cycle, which is the period during which the carrier signal c changes from its minimum value to its maximum value or from its maximum value to its minimum value. Also, the second command value m u ,m v ,m w The waveform is assumed to be positively and negatively symmetrical from phase 0° to 180° and from phase 180° to 360°, and inverted symmetrical from phase 0° to 90° and from phase 90° to 180°. In Embodiment 3, since the odd number Kc is set to 15, the second command value m u ,m v ,m w The fundamental wave's quarter period corresponds to 7.5 times the carrier's half period, but in order to maintain the symmetry of the phase voltage waveform, the second command value m is used in the first 0.5 periods. u ,m v ,m w Set to zero. Therefore, in this embodiment, it is only necessary to optimize seven values ​​corresponding to seven intervals of the carrier half-cycle, making optimization easy. Second command value m u ,m v ,m wSince the waveform has 7 degrees of freedom, the original optimal waveform can be reproduced by using the fundamental wave component and six harmonic components.

[0077] In Embodiment 3, the objective function f shown in the following equation (8) is used. obj The harmonic components included in the second command value are optimized to minimize the following.

[0078]

number

[0079] Here, the harmonic components are optimized so that the root of the sum of the squares of the values ​​obtained by dividing the nth harmonic voltage vn by its order n, i.e., the effective current of the load, is minimized. Here, n = 6i ± 1. However, certain frequency components, in this case the 11th and 13th harmonic components, are assumed to excite mechanical resonance in the load and cause large noise and torque pulsations, and these are preferentially reduced by increasing the weight of these order components. That is, the weight k in equation (8) n As shown in the following equation (9), the value is greater when n is 11 and when n is 13 than when n is not 11 or 13. This allows for reduced load loss while suppressing noise and torque pulsation.

[0080]

number

[0081] In this embodiment, the number of phases in the multiphase inverter circuit 3 and motor 4 is set to 3, and the waveforms of the three phases are shifted in phase by 120° from each other, so no harmonic components that are multiples of 3 are generated. Furthermore, since the voltage waveforms of each phase are positively and negatively symmetrical between phases 0° to 180° and phases 180° to 360°, no harmonic components that are multiples of 2 are generated. In addition, in the optimization process, harmonic components up to the 50th order are considered.

[0082] The waveform calculator 604C calculates the amplitude M and the fundamental wave phase θ.v Based on this, the second command value m u ,m v ,m w The waveform is calculated. For example, the second command value m of the u phase. u (M) is calculated using the following formula (10).

[0083]

number

[0084] Furthermore, the second command value of the three phase is m u ,m v ,m w Since the waveforms are shifted in phase by 120° from each other, the waveform calculator 604C calculates the fundamental wave phase θ of the u-phase. v Using this, the second command value m for the three phases u ,m v ,m w It can generate [this].

[0085] Figure 19 shows the second command value m according to Embodiment 3. u ,m v ,m w , carrier signal c and output phase voltage v u This figure shows the waveform. Figure 19 shows the case where the amplitude M = 0.8. The second command value m u ,m v ,m w The first command value v u * ,v v * ,v w * It consists of a fundamental wave component and harmonic components that include odd-order sinusoidal components. Here, the harmonic components include sinusoidal components whose frequencies are not integer multiples of the number of phases.

[0086] To explain the effects of the power converter 1C according to this embodiment, a comparative example using general carrier-synchronous PWM will be described. Figure 20 shows the phase voltage command value, carrier signal c, and output phase voltage v in the comparative example of Embodiment 3. uThis figure shows the waveform. The difference from Embodiment 3 shown in Figure 19 is that harmonic components are not superimposed on the phase voltage command value. The carrier signal c is the same as the example shown in Figure 19.

[0087] Here, the effective current value of the load, motor 4, is evaluated by WTHD, which is expressed by the above formula (6). Figure 21 shows the WTHD of the power converter 1C according to Embodiment 3. Figure 22 shows the WTHD of a comparative example of Embodiment 3. Comparing Figure 21 and Figure 22, it can be confirmed that the WTHD can be significantly reduced, particularly in the region where the amplitude M of the modulated voltage is large, thereby reducing the effective current value of the load, i.e., the loss. However, in the portion where the amplitude M is close to the maximum value, the power converter 1C according to Embodiment 3 is unable to reduce the WTHD compared to the comparative example. This is because the second command value m u ,m v ,m w This is because, despite the lack of flexibility to change the settings, the 11th and 13th harmonic components were prioritized for reduction.

[0088] Furthermore, the harmonic components included in the output phase voltage are compared between the power converter 1C according to Embodiment 3 and the comparative example. Figure 23 shows the magnitude of the harmonic components included in the output phase voltage of the power converter 1C according to Embodiment 3. Figure 24 shows the magnitude of the harmonic components included in the output phase voltage of the comparative example of Embodiment 3. In Figures 23 and 24, the horizontal axis represents the amplitude M, and the vertical axis represents the order of the harmonic frequency relative to the fundamental wave. Also, in Figures 23 and 24, the magnitude of the harmonic component is equal to the amplitude v of the output phase voltage. ph The value obtained by dividing by half the DC voltage is shown by the shade of color. By comparing Figures 23 and 24, it can be seen that the power converter 1C according to Embodiment 3 is able to significantly reduce specific frequency components, in this case the 11th and 13th harmonic components, which are assumed to excite mechanical resonance in the load and cause large noise and torque pulsation. The amplitudes of the 11th and 13th harmonic components are less than a few percent of the amplitude M of the fundamental wave component, confirming that they have been almost completely eliminated.

[0089] As explained above, in the power converter 1C according to Embodiment 3, the frequency of the carrier signal c is higher than that of the power converter 1A according to Embodiment 1. However, even in such a case, the frequency distribution of harmonics generated by the switching of the multiphase inverter circuit 3 can be optimized with a relatively simple configuration. As a result, the power converter 1C can achieve the same effects as Embodiment 1. Furthermore, in Embodiment 3, the modulation voltage generator 6C stores the amplitude of the fundamental wave component, the amplitude of the sine wave included in the harmonic component, and the multiple of the sine wave included in the harmonic component with respect to the fundamental wave component in the order amplitude memory device 606C, and uses the order amplitude memory device 606C to set the second command value m u ,m v ,m w This generates the first command value v u * ,v v * ,v w * The phase and frequency of the carrier signal c change transiently, and the phase-synchronized control of the carrier signal c is controlled by the first command value v u * ,v v * ,v w * Even while not fully following, the first command value v u * ,v v * ,v w * A voltage corresponding to this can be supplied to the load, which is the motor 4. Therefore, it becomes possible to control the voltage supplied to the motor 4 with high precision and high responsiveness. Furthermore, when the load is the motor 4, as in this embodiment, it becomes possible to control the speed and torque of the motor 4 with high precision and high responsiveness.

[0090] Here, the hardware configuration of the power converters 1A, 1B, and 1C according to Embodiments 1 to 3 will be described. Here, the power converters 1A, 1B, and 1C will be collectively referred to as power converter 1. The functions of power converter 1 can be realized using a processing circuit. Here, the functions of power converter 1 refer to the functions of the modulation voltage generators 6A, 6B, and 6C, the carrier signal generators 7A and 7B, and the gate signal generator 8. The processing circuit may be dedicated hardware such as the dedicated processing circuit 14 shown in Figure 25, or it may be the processor 15 and storage device 16 shown in Figure 26.

[0091] Figure 25 shows an example configuration of the power converter 1 when dedicated hardware is used. When dedicated hardware is used, the dedicated processing circuit 14 may be a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. Each of the multiple functions of the power converter 1 described above may be implemented by a different dedicated processing circuit 14, or the multiple functions of the power converter 1 may be implemented together by the dedicated processing circuit 14.

[0092] Figure 26 shows an example configuration of the power converter 1 when a processor and memory device are used. When using the processor 15 and memory device 16, each of the functions of the power converter 1 described above is realized by software, firmware, or a combination thereof. The software and firmware are written as programs, and the processor 15 reads and executes the programs stored in the memory device 16. These programs can also be said to cause the computer to execute the procedures and methods for each of the functions of the power converter 1.

[0093] The processor 15 is a CPU (Central Processing Unit), also known as a processing unit, arithmetic unit, microprocessor, microcomputer, or DSP (Digital Signal Processor). The storage device 16 is, for example, a non-volatile or volatile semiconductor memory such as ROM (Read Only Memory), EPROM (Erasable Programmable ROM), or EEPROM (Electrically EPROM), or a flexible disk, optical disk, compact disk, or DVD (Digital Versatile Disk). Furthermore, some of the functions of the power converter 1 may be implemented using dedicated hardware, while others may be implemented using software or firmware.

[0094] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention.

[0095] For example, in the above embodiment, the multiphase inverter circuit 3 is a three-phase inverter circuit, but it may be an inverter circuit with a different number of phases, or various inverter circuits such as a 3-level inverter or a 5-level inverter can be used.

[0096] Furthermore, in the above embodiment, the carrier signal generators 7A and 7B receive the first command value v u * ,v v * ,v w * When synchronizing the median value of the triangular wave, which is the carrier signal c, to phase 0°, the median value of the rising side of the triangular wave, phase 270° in the example of Figure 3, was used. However, the carrier signal generators 7A and 7B use the median value of the decreasing side of the triangular wave, phase 90° in the example of Figure 3, as the first command value v u * ,v v * ,vw * It may also be synchronized to a phase of 0°.

[0097] Furthermore, in the above embodiment, the carrier signal generators 7A and 7B generated a common carrier signal c for all phases, but individual carrier signals c for each phase may also be provided.

[0098] Furthermore, in the above embodiment, the second command value m u ,m v ,m w The carrier signal c is assumed to be constant during the carrier half-cycle, which is the period during which the carrier signal c changes from its minimum to its maximum value, or from its maximum value to its minimum value. However, if a high-speed computing device is available, a smoother second command value m is updated with a sufficiently short period relative to the carrier signal c. u ,m v ,m w You may also use [this].

[0099] In the above embodiment, the first command value v u * ,v v * ,v w * DC voltage v dc The second command value m is the modulation phase voltage command value obtained by dividing by half. u ,m v ,m w In contrast, by superimposing only odd-order sinusoidal components onto the fundamental wave component, a second command value m is obtained, which consists of the fundamental wave component and harmonic components that include at least one sinusoidal wave whose frequency is an odd multiple of the fundamental wave component. u ,m v ,m w Generates the second command value m u ,m v ,m w The waveform was optimized, but the original phase voltage command value, the first command value v u * ,v v * ,v w * Alternatively, only odd-order sinusoidal components may be superimposed on the fundamental wave component.

[0100] Furthermore, in Embodiments 1 and 2, the 5th and 7th harmonic components were preferentially reduced as specific frequency components, while in Embodiment 3, the 11th and 13th harmonic components were preferentially reduced. As explained above, considering the symmetry of the voltage waveform, harmonic components that are integer multiples of the number of phases and even-order harmonic components do not occur. In the case of three phases, the harmonic components can be expressed as 6k±1 harmonic components, where k is an integer. In addition to the examples given above, any component freely selected from the 6k±1 harmonic components can be preferentially reduced. [Explanation of Symbols]

[0101] 1, 1A, 1B, 1C Power converter, 2 DC power supply, 3 Multiphase inverter circuit, 4 Motor, 5 Motor controller, 6A, 6B, 6C Modulation voltage generator, 7A, 7B Carrier signal generator, 8 Gate signal generator, 14 Dedicated processing circuit, 15 Processor, 16 Memory device, 31, 31u, 31v, 31w Reg, 601, 701 Three-phase two-phase converter, 602 Amplitude calculator, 603, 702 Phase calculator, 604A, 604B, 604C Waveform calculator, 605 Waveform memory device, 606B, 606C Order amplitude memory device, 703A, 703B Carrier signal calculator.

Claims

1. A power converter that supplies power to a multiphase load based on a first command value which is a sinusoidal phase voltage command value, A multiphase inverter circuit in which two semiconductor switching elements having a reverse conduction function are connected in series between the positive and negative terminals of a DC power supply, and the same number of such legs are connected in parallel as the number of phases, and the terminals between the two semiconductor switching elements in each of the multiple legs are connected to the respective phases of the load, A modulation voltage generator that generates a second command value which is a modulation phase voltage command value composed of the fundamental wave component of the first command value and a harmonic component which includes at least one sine wave having an odd multiple of the frequency of the fundamental wave component, A carrier signal generator that generates a triangular wave carrier signal whose frequency is an odd multiple of the fundamental wave component of the first command value, and whose median value of the triangular wave is synchronized with the zero phase of the fundamental wave component of the first command value, A gate signal generator that generates a gate signal to drive the semiconductor switching element according to the comparison result between the second command value and the carrier signal, A power conversion device characterized by comprising the following features.

2. The harmonic component included in the second command value is characterized by including at least one sine wave whose frequency is an odd multiple of the fundamental wave component of the first command value and which is not an integer multiple of the number of phases of the multiphase inverter circuit. The power conversion device according to claim 1.

3. The modulation voltage generator is characterized by storing the second command value, which corresponds to one-quarter of the period of the fundamental wave component of the first command value, in a storage device, and generating the second command value using the storage device. The power conversion device according to claim 1.

4. The modulation voltage generator is characterized by storing the amplitude of the fundamental wave component, the amplitude of the sine wave included in the harmonic component, and the multiple of the frequency of the sine wave included in the harmonic component relative to the fundamental wave component in a memory device, and generating the second command value using the memory device. The power conversion device according to claim 1.

5. The carrier signal generator generates the carrier signal having a frequency nine times that of the fundamental wave component. The aforementioned harmonic components are characterized by including sine waves of three frequencies. A power conversion device according to any one of claims 1 to 4.

6. The harmonic components are characterized by including sine waves with frequencies three, five, and seven times that of the fundamental wave component. The power conversion device according to claim 5.

7. The carrier signal generator generates the carrier signal having a frequency 15 times that of the fundamental wave component. The aforementioned harmonic components are characterized by including sine waves of six frequencies. A power conversion device according to any one of claims 1 to 4.

8. The harmonic components are characterized by including sine waves with frequencies 3, 5, 7, 9, 11, and 13 times that of the fundamental wave component. The power conversion device according to claim 7.

9. The multiple of the frequency of the carrier signal to the fundamental wave component is characterized by being odd and an integer multiple of the number of phases in the multiphase inverter circuit. A power conversion device according to any one of claims 1 to 4.

10. The modulation voltage generator is characterized in that it maintains the second command value at a constant value during a carrier half-cycle, which is the period during which the carrier signal changes from a minimum value to a maximum value or the period during which the carrier signal changes from a maximum value to a minimum value. A power conversion device according to any one of claims 1 to 4.

11. The effective current value of the load is lower compared to the case where the second command value does not include the harmonic components. A power conversion device according to any one of claims 1 to 4.

12. Compared to the case where the second command value does not include the harmonic components, the amplitude of the predetermined frequency components included in the phase voltage of the load is lower. A power conversion device according to any one of claims 1 to 4.

13. A control method for a power converter that supplies power to a multiphase load based on a first command value which is a sinusoidal phase voltage command value, comprising a multiphase inverter circuit in which two semiconductor switching elements having a reverse conduction function are connected in series between the positive and negative terminals of a DC power supply, and the same number of such legs are connected in parallel as the number of phases, and the terminals between the two semiconductor switching elements in each of the multiple legs are connected to the respective phases of the load, wherein the power converter has a first command value which is a sinusoidal phase voltage command value, The steps include generating a second command value which is a modulation phase voltage command value composed of the fundamental wave component of the first command value and a harmonic component which includes at least one sine wave whose frequency is an odd multiple of the fundamental wave component, The steps include generating a triangular wave carrier signal whose frequency is an odd multiple of the fundamental wave component of the first command value, and such that the median of the triangular wave is synchronized to the zero phase of the fundamental wave component of the first command value, The steps include generating a gate signal to drive the semiconductor switching element according to the comparison result between the second command value and the carrier signal, A control method for a power conversion device, characterized by including the following:

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