Power conversion device and method for controlling power conversion device

Abstract

A power conversion device (1A) for supplying power to a multi-phase load on the basis of a first command value, which is a sinusoidal phase voltage command value, is provided with: a multi-phase inverter circuit (3) in which branches are connected in parallel between positive and negative terminals of a DC power source, said branches being formed by connecting two semiconductor switching elements having a reverse conduction function in series, the number of branches being the same as the number of phases; a terminal between the two semiconductor switching elements of each branch is connected to each phase of a load; a modulation voltage generator (6A) that generates a second command value including a fundamental component including the first command value and a higher harmonic component including at least one sine wave having an odd number of frequencies with respect to the fundamental component; a carrier signal generator (7A) that generates a carrier signal of a triangular wave such that the frequency is odd multiples of the fundamental component of the first command value and the median of the triangular wave is zero-synchronized with the phase of the fundamental component of the first command value; and a strobe signal generator (8) that generates a strobe signal for driving the semiconductor switching element on the basis of the result of comparison between the second command value and the carrier signal.

Description

Technical Field

[0001] The present disclosure relates to a power conversion device for converting DC power into AC power and a control method for the power conversion device. Background Art

[0002] Inverters are widely used as power conversion devices that convert DC power into AC power. The inverter compares a sinusoidal modulation signal with a triangular carrier signal, switches the semiconductor switching element on and off, and outputs a sinusoidal phase voltage. However, switching generates higher harmonics in the phase voltage. For example, in the phase voltage, when the frequency of the phase voltage is set to f s , set the frequency of the carrier signal to f c In the case of c ±2f s The frequency components A and f c ±4f s The harmonics of the frequency component B increase the load loss and cause noise and torque ripple.

[0003] The technology disclosed in Patent Document 1 disperses the ratio of frequency component A to frequency component B contained in the phase voltage by superimposing higher harmonic components on a sinusoidal modulation signal. Patent Document 1 also explains that dispersing the ratio of frequency component A to frequency component B contained in the phase voltage can reduce load losses.

[0004] Prior art literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-072935 Summary of the Invention

[0006] However, according to the above-mentioned previous technology, when the frequency of the noise and torque pulsation generated by frequency component A becomes the same frequency as the frequency of the noise and torque pulsation generated by frequency component B, there is a problem that the noise and torque pulsation cannot be reduced even if the ratio of frequency component A and frequency component B is dispersed.

[0007] For example, when the number of phases in the inverter is 3 and f c =9f s In the case of s and 11f s , the frequency of frequency component B becomes 5f s and 13f s When considering the noise generated by the frequency component A and the frequency of the torque ripple, 7f s It is the positive phase component, so it becomes 6f s, 11f s It is the anti-phase component, so it becomes 12f s Similarly, when considering the noise generated by frequency component B and the frequency of torque ripple, 5f s It is the anti-phase component, so it becomes 6f s , 13f s It is the positive phase component, so it becomes 12f s That is, in the above case, even if the ratio of the frequency component A to the frequency component B is dispersed, noise and torque ripple having a common frequency between the two components are generated, and therefore these cannot be reduced.

[0008] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a power conversion device that can effectively suppress noise and torque ripple generated by switching of an inverter and reduce load losses caused by higher harmonic components.

[0009] In order to solve the above-mentioned problems and achieve the purpose, the power conversion device disclosed in the present invention is a power conversion device that supplies power to a multi-phase load based on a first command value that is a sinusoidal phase voltage command value, and is characterized by comprising: a multi-phase inverter circuit, in which a number of branches consisting of two semiconductor switching elements with a reverse conduction function connected in series are connected in parallel between the positive and negative terminals of a DC power supply, the same number as the number of phases, and the terminals between the two semiconductor switching elements in each of the multiple branches are connected to each phase of the load; and a modulation voltage generator that generates a phase voltage for modulation. a second command value of the command value, the second command value including a fundamental wave component of the first command value and a higher harmonic component, the higher harmonic component including at least one sine wave having an odd-integer frequency relative to the fundamental wave component; a carrier signal generator generating a triangular wave carrier signal in such a manner that the frequency is an odd-integer frequency relative to the fundamental wave component of the first command value and the median of the triangular wave is synchronized with the phase zero of the fundamental wave component of the first command value; and a gate signal generator generating a gate signal for driving the semiconductor switching element based on a comparison result between the second command value and the carrier signal.

[0010] According to the present disclosure, it is possible to effectively suppress noise and torque ripple generated by switching of the inverter and reduce load loss due to harmonic components. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a diagram showing the configuration of the power conversion device according to the first embodiment.

[0012] Figure 2 It shows Figure 1 The structure of the carrier signal generator is shown in the figure.

[0013] Figure 3 It is shown by Figure 2 Figure 1 shows a diagram of a carrier signal generated by a carrier signal operator.

[0014] Figure 4 It shows Figure 2 FIG. 1 is a diagram showing an example of a carrier signal generated by a carrier signal operator.

[0015] Figure 5 It's about Figure 1 The diagram is for explaining the operation of the strobe signal generator shown.

[0016] Figure 6 This is a diagram showing an example of the phase voltage output by the power conversion device when the second command value in the form of a sine wave is supplied to the gate signal generator.

[0017] Figure 7 It shows Figure 1 The structure of the modulation voltage generator is shown in the figure.

[0018] Figure 8 This is a diagram showing waveforms of the second command value, the carrier signal, and the output phase voltage in the first embodiment.

[0019] Figure 9 1 is a diagram showing waveforms of phase voltage command values, carrier signals, and output phase voltages in a comparative example of the first embodiment.

[0020] Figure 10 This is a diagram showing the WTHD of the power conversion device according to the first embodiment.

[0021] Figure 11 This is a diagram showing WTHD in a comparative example of the first embodiment.

[0022] Figure 12 This is a diagram showing the magnitude of harmonic components included in the output phase voltage of the power conversion device according to the first embodiment.

[0023] Figure 13 1 is a diagram showing the magnitude of harmonic components included in the output phase voltage in a comparative example of the first embodiment.

[0024] Figure 14 This is a diagram showing the configuration of a power conversion device according to a second embodiment.

[0025] Figure 15 It shows Figure 14 The structure of the modulation voltage generator is shown in the figure.

[0026] Figure 16 This is a diagram showing the configuration of a power conversion device according to a third embodiment.

[0027] Figure 17 It shows Figure 16 The structure of the carrier signal generator is shown in the figure.

[0028] Figure 18 It shows Figure 16 The structure of the modulation voltage generator is shown in the figure.

[0029] Figure 19 This is a diagram showing waveforms of the second command value, the carrier signal, and the output phase voltage in the third embodiment.

[0030] Figure 20 1 is a diagram showing waveforms of phase voltage command values, carrier signals, and output phase voltages in a comparative example of the third embodiment.

[0031] Figure 21 This is a diagram showing the WTHD of the power conversion device according to the third embodiment.

[0032] Figure 22 This is a diagram showing WTHD in a comparative example of the third embodiment.

[0033] Figure 23 This is a diagram showing the magnitude of harmonic components included in the output phase voltage of the power conversion device according to the third embodiment.

[0034] Figure 24 1 is a diagram showing the magnitude of harmonic components included in the output phase voltage in a comparative example of the third embodiment.

[0035] Figure 25 This is a diagram showing a configuration example of a power conversion device using dedicated hardware.

[0036] Figure 26 This is a diagram showing a configuration example of a power conversion device using a processor and a storage device. DETAILED DESCRIPTION

[0037] Hereinafter, a power conversion device and a method for controlling the power conversion device according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0038] Implementation method 1.

[0039] Figure 1 This figure shows the structure of a power conversion device 1A according to Embodiment 1. Power conversion device 1A includes a multiphase inverter circuit 3 connected to a DC power supply 2 and a motor 4 as a load, a modulation voltage generator 6A, a carrier signal generator 7A, and a gate signal generator 8.

[0040] The multi-phase inverter circuit 3 converts the DC power of the DC power supply 2 into multi-phase AC power and outputs it to the motor 4. In addition, the number of phases of the multi-phase inverter circuit 3 is 3, and each phase is set as the u phase, the v phase, and the w phase. The multi-phase inverter circuit 3 is a structure obtained by connecting branches 31 formed by connecting two semiconductor switching elements Q with a reverse conduction function in series in parallel for the number of phases. In addition, the number of phases of the multi-phase inverter circuit 3 is 3, so the multi-phase inverter circuit 3 has 6 semiconductor switching elements Q, such as Figure 1 As shown, the six semiconductor switching elements Q are respectively referred to as semiconductor switching elements Q up , Q un , Q vp , Q vn , Q wp , Q wn In addition, the semiconductor switching element Q on the positive side corresponding to u up and the negative side semiconductor switching element Q un The branch formed by the series connection is called branch 31u, and the semiconductor switching element Q on the positive side corresponding to v is connected. vp and the negative side semiconductor switching element Q vn The branch formed by the series connection is called branch 31v. The semiconductor switching element Q1 corresponding to the positive side of w is connected to the positive side of w. wp and the negative side semiconductor switching element Q wn The series-connected branches are referred to as branches 31w. The middle terminals of each branch 31 are connected to the respective phases of the motor 4. Here, each semiconductor switching element Q comprises an IGBT (Insulated Gate Bipolar Transistor) and an antiparallel diode. Furthermore, if a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or RC (Reverse Conducting) IGBT is used instead of the IGBT, the antiparallel diode can be omitted.

[0041] The motor controller 5 calculates a first command value v as a sinusoidal phase voltage command value as a voltage to be supplied to the motor 4 based on the torque command value of the motor 4. u * 、v v * 、v w * The motor controller 5 calculates the first command value v u * 、v v * 、v w* They are output to the modulation voltage generator 6A and the carrier signal generator 7A respectively.

[0042] The modulation voltage generator 6A generates a first command value v u * 、v v * 、v w * , generating the second command value m as the phase voltage command value for modulation u 、m v 、m w The modulation voltage generator 6A generates the second command value m u 、m v 、m w Output to the strobe signal generator 8. In addition, the carrier signal generator 7A generates a first instruction value v u * 、v v * 、v w * , generating a triangular wave carrier signal c. The carrier signal generator 7A outputs the generated carrier signal c to the gate signal generator 8. The gate signal generator 8 compares the second command value m with the generated carrier signal c. u 、m v 、m w The magnitude of the carrier signal c is used to generate a gate signal g that controls the on and off of the semiconductor switching element Q of the multi-phase inverter circuit 3. up 、g un 、g vp 、g vn 、g wp 、g wn . Selection signal g up 、g un 、g vp 、g vn 、g wp 、g wn Each corresponds to a semiconductor switching element Q up , Q un , Q vp , Q vn , Q wp , Q wn , so that the corresponding semiconductor switch element Q is turned on or off. In addition, without distinguishing the selection signal g up 、g un 、g vp 、g vn 、g wp 、g wn In each case, it is simply referred to as the selection signal g.

[0043] Figure 2 It shows Figure 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.

[0044] The three-phase to two-phase converter 701 converts the first command value v on the three-phase coordinates into u * 、v v * 、v w * The first command value v on the two-phase coordinate α * 、v β * Performing three-phase to two-phase conversion The three-phase to two-phase converter 701 can perform three-phase to two-phase conversion using, for example, the following formula (1).

[0045] [Mathematical formula 1]

[0046]

[0047] The phase calculator 702 calculates the first command value v on the two-phase coordinates. α * 、v β * The fundamental phase θ of the U phase v Specifically, first, for the first command value v on the two-phase coordinate α * 、v β * Perform the inverse tangent operation to find v α * The phase of v u * However, for the first command value v on the two-phase coordinate α * 、v β * v obtained by performing the inverse tangent operation α * The phase of is the cosine signal reference, so by subtracting "π / 2" from this phase, the phase of the sin signal reference can be obtained.

[0048] In addition, here the first command value v u * 、v v * 、v w * And the first command value v α * 、vβ * The description is based on the premise that the waveform has a sufficiently small number of harmonic components and is the same as the fundamental component. u * 、v v * 、v w * And the first command value v α * 、v β * When a large number of higher harmonic components are included, the fundamental wave component can be extracted by passing the signal through a low-pass filter or the like.

[0049] The carrier signal operator 703A first operates a carrier signal c having a frequency that is an odd number Kc times the fundamental wave component. Specifically, the carrier signal phase is generated by multiplying the fundamental wave phase θv by the odd number Kc. The carrier signal operator 703A generates the following: Figure 3 The triangle wave carrier signal c is shown. Figure 3 It is shown by Figure 2 The carrier signal generated by the carrier signal operator 703A is shown in FIG. Moreover, the carrier signal operator 703A performs phase synchronization control to correct the phase of the carrier signal c so that the median value of the triangular wave overlaps the phase 0° of the phase voltage command value. In addition, Figure 3 In the example shown, the median value of the triangular wave is 0. The carrier signal operator 703A outputs the carrier signal c after performing phase synchronization control to the gate signal generator 8.

[0050] In this embodiment, the odd number Kc is set to 9, so that the phase 270° of the carrier signal c is synchronized with the phase 0° of the phase voltage command value. Figure 4 shown. Figure 4 It shows Figure 2 1 shows an example of a carrier signal c generated by carrier signal calculator 703A. In this embodiment, carrier signal c is synchronized with the phase of the u-phase voltage, and a common carrier signal c is used for all three phases. Therefore, the odd number Kc that determines the frequency of carrier signal c is set to a multiple of the number of phases, 3.

[0051] Return to Figure 1 The gate signal generator 8 converts the second command value m outputted by the modulation voltage generator 6A as the phase voltage command value for modulation into a second command value m. u 、m v 、m w Each is compared with the carrier signal c to generate a signal for the semiconductor switching element Q of the multi-phase inverter circuit 3. up , Q un, Q vp , Q vn , Q wp , Q wn The selection signal g that controls the on and off of each up 、g un 、g vp 、g vn 、g wp 、g wn . Selection signal g up 、g un 、g vp 、g vn 、g wp 、g wn Each takes a high "H" or low "L" value. When the value of the selection signal g is "H", the semiconductor switch element Q corresponding to the selection signal g is controlled to be turned on, and when the value of the selection signal g is "L", the semiconductor switch element Q corresponding to the selection signal g is controlled to be turned off.

[0052] Figure 5 It's about Figure 1 The diagram is for explaining the operation of the strobe signal generator 8. Figure 5 The gate signal generator 8 compares the second command value m u and carrier signal c, generating the selection signal g up and g un Specifically, here the second instruction value m u When it is greater than the carrier signal c, the selection signal g up Set the value of "H" and select the signal g un The value of the second instruction value m is set to "L". u When the signal is less than the carrier signal c, the selection signal g up Set the value of "L" to select the signal g un The value of is set to "H". up and g un They are complementary to each other. That is, when the selection signal g up When it is "H", the selection signal g un is "L", the selection signal g up When it is "L", the selection signal g un Becomes "H". up When it is "H", the positive side semiconductor switching element Q up When the output phase voltage is turned on, u Become a v dc / 2, in the strobe signal g un When it is “H”, the negative side semiconductor switching element Q un When the output voltage is turned on, ubecomes -v dc / 2. In the period of carrier signal c, the output phase voltage v u When averaging is performed, the first instruction value v is obtained. u * Phase voltage.

[0053] Here, by examining the harmonic components that are assumed to be generated when the carrier signal c generated by the carrier signal generator 7A and the gate signal generator 8 described above are used, the second command value m generated by the modulation voltage generator 6A is considered. u 、m v 、m w . Figure 6 The second command value m is a sine wave. u This figure shows an example of the phase voltage output by the power conversion device 1A when the gate signal generator 8 is supplied. Figure 6 In the figure, regarding the u-phase portion, the second command value m is shown as a phase voltage command value for sinusoidal modulation using the carrier signal c and the gate signal generator 8. u 、m v 、m w The waveform of the phase voltage output when the multi-phase inverter circuit 3 is operated by generating the gate signal g. Figure 6 The upper part shows the second sine wave instruction value m u And the triangular wave carrier signal c, in Figure 6 The lower part shows the second command value m according to the sine wave u And the triangular wave carrier signal c outputs the output phase voltage v u Based on the knowledge of Fourier series expansion, the output phase voltage v output by the power conversion device 1A is represented by the sum of sine wave components and cosine wave components of various orders. u Here, the phase voltage becomes positive and negative symmetrical in the phases 0° to 180° and 180° to 360°, so the even-order harmonic components are removed first. Next, the phase voltage becomes inverted in the phases 0° to 90° and 90° to 180°, and the cosine wave components are also removed. Therefore, when using the carrier signal c of this embodiment, the harmonic components of the phase voltage become only odd-order sine wave components. In addition, based on this result, when the first command value v is set, u * 、v v * 、v w * Or the second command value m u 、m v 、m wWhen the phase voltage waveform is optimized by superimposing the higher harmonic components, the first command value v u * 、v v * 、v w * Or the second command value m u 、m v 、m w Only the sine wave components that overlap an odd number of times are sufficient.

[0054] Figure 7 It shows Figure 1 The modulation voltage generator 6A includes a three-phase to two-phase converter 601 , an amplitude calculator 602 , a phase calculator 603 , a waveform calculator 604A, and a waveform storage device 605 .

[0055] The three-phase to two-phase converter 601 performs the same processing as the three-phase to two-phase converter 701, and converts the first command value v, which is a sinusoidal phase voltage command value on the three-phase coordinate, into a value. u * 、v v * 、v w * The first command value v on the two-phase coordinate α * 、v β * The three-phase to two-phase converter 601 converts the first command value v on the two-phase coordinates into α * 、v β * The signal is output to the amplitude calculator 602 and the phase calculator 603 .

[0056] The amplitude calculator 602 first calculates the first command value v on the two-phase coordinates. α * 、v β * Calculate the first command value v α * 、v β * The amplitude v php For example, the amplitude calculator 602 can calculate the first command value v using the following formula (2): α * 、v β * The amplitude v php .

[0057] [Mathematical formula 2]

[0058]

[0059] Next, the amplitude calculator 602 converts the calculated first command value v into α * 、v β * The amplitude v php Divide by half the DC voltage to convert it into the second command value m as the voltage command value for modulation. u 、m v 、m w The amplitude calculator 602 outputs the amplitude M as the calculation result to the waveform calculator 604A.

[0060] [Mathematical formula 3]

[0061]

[0062] The phase calculator 603 calculates the first command value v on the two-phase coordinates by the same processing as the phase calculator 702. α * 、v β * The fundamental phase θ of the u phase v The phase operator 603 converts the fundamental wave phase θ obtained as the calculation result into v Output to waveform operator 604A.

[0063] The waveform calculator 604A uses the amplitude M and the fundamental wave phase θ of the u-phase v , calculate the second instruction value m u 、m v 、m w Specifically, the first instruction value v u * 、v v * 、v w * The second command value m corresponding to the quarter cycle of the fundamental wave phase 0° to 90° u 、m v 、m w The waveform is stored in the waveform storage device 605 in advance, and the second instruction value m is generated by using the stored waveform. u 、m v 、m w Here, the waveform calculator 604A uses the phase voltage, that is, the second command value m u 、m v 、m wThe waveform of the fundamental wave corresponding to one-quarter period of the fundamental wave is reproduced from the waveform corresponding to the waveform of the phase voltage command value for modulation of the three phases, which is a waveform with a phase shift of 120 degrees. Therefore, the waveform calculator 604A uses the fundamental wave phase θ of the u phase. v After generating the u-phase waveform, the second command value m for the three-phase portion can be generated by shifting the phase. u 、m v 、m w .

[0064] In this embodiment, when the carrier signal c generated by the carrier signal generator 7A is used, the second command value m stored in the waveform storage device 605 is generated so that the fundamental component of the phase voltage becomes the command value and the higher harmonic components are optimized. u 、m v 、m w Here, in this embodiment, by the first instruction value v u * 、v v * 、v w * The optimal second command value m can be obtained by a simple method in which the fundamental wave component of the sine wave component of odd order as a higher harmonic component is superimposed. u 、m v 、m w .

[0065] As a method for superimposing higher harmonic components on phase voltage command values, International Publication No. 2019 / 016901 discloses a method for superimposing third-order higher harmonics on a three-phase inverter circuit. In this method, by superimposing higher harmonics whose frequencies are integer multiples of the number of phases, it is possible to effectively utilize the voltage on the DC side and supply a larger AC voltage to the load without changing the output voltage on the load side of the multi-phase inverter circuit 3. In contrast, in this embodiment, higher harmonic components, i.e., sine waves, whose frequencies are not integer multiples of the number of phases, are also superimposed on the phase voltage command values. Thus, the frequency distribution of higher harmonic components generated by the switching of the multi-phase inverter circuit 3 can be optimized.

[0066] In this embodiment, the second command value m is set to 0 in the carrier half cycle, which is a period when the carrier signal c changes from the minimum value to the maximum value or a period when the carrier signal c changes from the maximum value to the minimum value. u 、m v 、m wIn this embodiment, the odd number Kc is set to 9, so the quarter cycle of the fundamental wave stored in the waveform storage device 605 is equivalent to 4.5 times the half cycle of the carrier wave. However, in order to maintain the symmetry of the phase voltage waveform, the second command value m is set to 9 in the first 0.5 cycle. u 、m v 、m w Therefore, in this embodiment, only four values ​​corresponding to four intervals of a carrier half cycle need to be optimized and stored, which makes optimization easy.

[0067] In addition, it is assumed here that the second command value m for one phase is stored. u 、m v 、m w The waveform is a quarter-cycle portion of the fundamental wave, but in the case of storing waveforms of multiple phase portions, the storage period can be reduced. When the number of phases is 3, during the period when the phase of the u-phase voltage is 0° to 30°, the phase of the v-phase voltage becomes -120° to -90°, that is, 240° to 270°. This waveform becomes a waveform obtained by reversing the positive and negative of the waveform during the period from 60° to 90° of the u-phase voltage when considering the symmetry of the waveform. Next, during the period when the phase of the u-phase voltage is 0° to 30°, the phase of the w-phase voltage becomes -240° to -210°, that is, 120° to 150°. This waveform becomes a waveform obtained by reversing the waveform during the period from 30° to 60° of the u-phase voltage in the time direction, that is, the phase direction when considering the symmetry of the waveform. Therefore, when storing the second instruction value m for the three-phase portion, u 、m v 、m w In the case of a waveform of a phase of 0° to 30°, if the waveform of the phase period is stored, the waveform of the phase period of 0° to 90° can be reproduced. u 、m v 、m w In the case of a waveform, a waveform corresponding to a period obtained by dividing a 90° period, which is a quarter cycle portion of the fundamental wave, by the number of phases may be stored.

[0068] In this embodiment, the objective function f represented by the following formula (4) is obj The higher harmonic components of the phase voltage are optimized in a minimized manner.

[0069] [Formula 4]

[0070]

[0071] In addition, here, the higher harmonic components are optimized in such a way that the square root of the sum of the squares of the values ​​obtained by dividing the nth-order higher harmonic voltage vn by its order n, that is, the effective value of the load current, becomes the minimum. Here, n is set to 6i ± 1. It is assumed that certain frequency components, here the 5th and 7th-order higher harmonic components, will excite the mechanical resonance of the load and cause large noise and torque ripple. By increasing the weighting of these order components, they are preferentially reduced. That is, the weight k in formula (4) is n As shown in the following formula (5), when n is 5 and when n is 7, it is larger than when n is other than 5 and 7. This can reduce the load loss while suppressing noise and torque ripple.

[0072] [Formula 5]

[0073]

[0074] In this embodiment, the multiphase inverter circuit 3 and motor 4 have three phases, and the three-phase waveforms are configured with phases offset by 120°. This prevents the generation of harmonic components that are multiples of three. Furthermore, the voltage waveforms of each phase are positively and negatively symmetrical between phases 0° to 180° and 180° to 360°, preventing the generation of harmonic components that are multiples of two. Furthermore, during optimization, harmonic components up to the 50th order were considered.

[0075] Figure 8 The second command value m in the first embodiment is shown. u 、m v 、m w , carrier signal c and output phase voltage v u The waveform of . Figure 8 In FIG. 1 , the case where the amplitude M=0.8 is shown. The second command value m u 、m v 、m w Including the first instruction value v u * 、v v * 、v w * The fundamental wave component and the higher harmonic components containing the odd-order sinusoidal wave components. Here, the higher harmonic components include sinusoidal wave components whose frequencies are not integer multiples of the number of phases. Specifically, in the second command value m u 、m v 、m w The sine wave components with frequencies 3, 5, 7, 11, 13, 15, 17, 19, and 21 times the fundamental wave component are superimposed. In addition, the sine wave components with frequencies 21 times the fundamental wave component are recorded here, but in the second command value m u 、mv 、m w There is a higher frequency sine wave component superimposed on it. The output phase voltage v u The phases 0° to 180° and 180° to 360° are positively and negatively symmetrical, and the phases 0° to 90° and 90° to 180° are reversely symmetrical. u 、m v 、m w It is a constant value in the carrier half cycle.

[0076] Here, in order to illustrate the effects of the power conversion device 1A according to the present embodiment, a comparative example using general carrier-synchronized PWM (Pulse Width Modulation) will be described. Figure 9 The phase voltage command value, the carrier signal c, and the output phase voltage v in the comparative example of the first embodiment are shown. u The waveform of . Figure 8 The difference of the example of the embodiment 1 shown is that no higher harmonic components are superimposed on the phase voltage command value. Figure 8 The same signal is shown in the example.

[0077] Here, the effective current value of the motor 4 as a load is evaluated using WTHD represented by the following formula (6).

[0078] [Formula 6]

[0079]

[0080] The numerator of formula (6) is the square root of the sum of the squares of the values ​​obtained by dividing the nth-order harmonic voltage vn by its order n, i.e., a value equivalent to the effective value of the load current. By dividing this effective value of the current by the amplitude v1 of the fundamental voltage in the denominator, WTHD becomes a value equivalent to the current distortion factor.

[0081] Here, the values ​​of WTHD are compared between the power conversion device 1A of the present embodiment and the comparative example. Figure 10 This is a diagram showing the WTHD of the power conversion device 1A according to the first embodiment.

[0082] Figure 11 This is a diagram showing WTHD in a comparative example of embodiment 1. Figure 10 and Figure 11 It was confirmed that WTHD can be significantly reduced, particularly in a region where the amplitude M of the modulation voltage is large, thereby reducing the effective value of the load current, that is, the loss.

[0083] Furthermore, the harmonic components included in the output phase voltage are compared between the power conversion device 1A of the present embodiment and the comparative example. Figure 12 This is a diagram showing the magnitude of harmonic components included in the output phase voltage of the power conversion device 1A according to the first embodiment. Figure 13 : is a diagram showing the magnitude of the higher harmonic components included in the output phase voltage in the comparative example of the first embodiment. Figure 12 as well as Figure 13 In the figure, the horizontal axis is the amplitude M, and the vertical axis represents the frequency of the higher harmonics, which is expressed in terms of the order of the fundamental wave. Figure 12 as well as Figure 13 In the figure, the magnitude of the higher harmonic components is expressed by the intensity of the colors to represent the amplitude v of the output phase voltage. ph The value obtained by dividing by half the DC voltage. Figure 12 as well as Figure 13 As can be seen, the power conversion device 1A of this embodiment can significantly reduce specific frequency components, specifically the fifth and seventh harmonic components, which are assumed to cause large noise and torque ripple by exciting mechanical resonance of the load. The amplitudes of the fifth and seventh harmonic components are less than a few percent of the amplitude M, the amplitude of the fundamental component, confirming their near-elimination.

[0084] As described above, the power conversion device 1A according to the first embodiment is configured to generate a first command value v which is a sinusoidal phase voltage command value. u * 、v v * 、v w * , supplying power to the motor 4 as a multi-phase load. The power conversion device 1A comprises: a multi-phase inverter circuit 3, in which a number of branches 31, each consisting of two semiconductor switching elements Q having a reverse conduction function connected in series, are connected in parallel between the positive and negative terminals of the DC power supply 2, the same number as the number of phases, and the terminals between the two semiconductor switching elements Q in each of the plurality of branches 31 are connected to each phase of the motor 4 as a load; a modulation voltage generator 6A, which generates a second command value m as a phase voltage command value for modulation. u 、m v 、m w , the second instruction value m u 、m v 、m w Including the first instruction value v u * 、v v * 、v w * The fundamental wave component and the sine wave having an odd multiple of the fundamental wave component frequency include at least one higher harmonic component; the carrier signal generator 7A so that 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 equal to the first command value v u * 、v v * 、v w * The phase of the fundamental component of zero is synchronized to generate a triangular wave carrier signal c; and the selection signal generator 8, according to the second instruction value m u 、m v 、m w The comparison result of the magnitude relationship with the carrier signal c generates a gate signal g for driving each of the plurality of semiconductor switching elements Q of the multi-phase inverter circuit 3 .

[0085] The triangular wave carrier signal c has the following characteristics: u * 、v v * 、v w * The frequency of the fundamental wave component is an odd multiple, and the median of the triangular wave is equal to the first command value v u * 、v v * 、v w * The characteristic of synchronizing with the phase zero of the fundamental wave component of the carrier signal c is that when the multiphase inverter circuit 3 is driven by the selection signal g generated by the carrier signal c, the generated phase voltage becomes positive and negative symmetrical in the phases 0° to 180° and 180° to 360°, and becomes reverse symmetrical in the phases 0° to 90° and 90° to 180°. Therefore, the phase voltage does not contain even-order harmonic components or cosine wave components, and the harmonic components contained in the phase voltage become only odd-order sine wave components. Therefore, by making the second command value m u 、m v 、m w Including the first instruction value v u * 、v v * 、v w *By including at least one higher harmonic component of a fundamental wave component and a sine wave having an odd-number multiple of the fundamental wave frequency, the higher harmonic components contained in the output phase voltage can be suppressed. With a relatively simple structure, the frequency distribution of the higher harmonics generated by the switching of the multiphase inverter circuit 3 can be optimized. This effectively suppresses the frequency components that generate load noise and torque ripple, while also reducing load losses caused by the higher harmonic components.

[0086] In addition, the second command value m u 、m v 、m w The higher harmonic components can contain at least one relative to the first command value v u * 、v v * 、v w * The fundamental wave component of the multi-phase inverter circuit 3 is a sine wave whose frequency is an odd multiple and not an integral multiple of the number of phases of the multi-phase inverter circuit 3.

[0087] In addition, the modulation voltage generator 6A sets the first command value v u * 、v v * 、v w * The second command value m corresponding to one quarter cycle of the fundamental wave component u 、m v 、m w The waveform storage device 605 can be used to generate the second command value m u 、m v 、m w As described above, by making the carrier signal c relative 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 equal to the first command value v u * 、v v * 、v w * The generated phase voltage becomes positive and negative symmetrical in the phases 0° to 180° and 180° to 360°, and becomes reverse symmetrical in the phases 0° to 90° and 90° to 180°. Therefore, it is only necessary to store the second command value m corresponding to one quarter of the fundamental wave component. u 、m v 、mw , it is possible to generate the second instruction value m for one cycle by utilizing the above characteristics. u 、m v 、m w .

[0088] The frequency of the carrier signal c can be an odd number and an integral multiple of the number of phases of the multiphase inverter circuit 3. This allows the carrier signal c to be synchronized with the phase voltage of any phase, and a common carrier signal c can be used in multiple phases.

[0089] The modulation voltage generator 6A sets the second command value m to 1 in a carrier half cycle, which is a period when the carrier signal c changes from the minimum value to the maximum value or a period when the carrier signal c changes from the maximum value to the minimum value. u 、m v 、m w The value is kept constant. Thus, the number of values ​​stored in the waveform storage device 605 can be reduced, and the required storage capacity can be suppressed. Specifically, in the first embodiment, Kc=9, and a quarter cycle of the fundamental wave component is equivalent to 4.5 times the half cycle of the carrier wave. In the first 0.5 cycle, the second instruction value m is set to u 、m v 、m w Becomes zero, so only the four second command values ​​m u 、m v 、m w Just optimize and store, easy to optimize.

[0090] Furthermore, as described above using the formula (4), in the power conversion device 1A, the second command value m u 、m v 、m w Compared with the case where the second command value m does not include the higher harmonic components, u 、m v 、m w It is optimized to reduce the effective value of the load current. In addition, at this time, by using the weighting coefficient shown in formula (5), the second command value m u 、m v 、m w Compared with the case where the second command value m does not include the higher harmonic components, u 、m v 、m w It is optimized so as to reduce the amplitude of predetermined frequency components, for example, the fifth and seventh harmonic components.

[0091] Implementation method 2.

[0092] Figure 14This diagram shows the configuration of a 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 includes a modulation voltage generator 6B in place of the modulation voltage generator 6A of power converter 1A according to Embodiment 1. Below, descriptions of common components with power converter 1A according to Embodiment 1 are omitted, and the main focus will be on components that differ from power converter 1A.

[0093] In the phase synchronization control for synchronizing the phase of the carrier signal c with the phase voltage command value of the load, when the phase and frequency of the voltage to be supplied to the load change transiently, an identification time is required for synchronizing the carrier signal c with the phase voltage command value. In the first embodiment, the second command value m is generated based on the phase of the carrier signal c. u 、m v 、m w , so the phase of the carrier signal c and the first command value v u * 、v v * 、v w * During the period of incomplete synchronization, the second command value m u 、m v 、m w That is, the phase voltage of the load is not synchronized with the first command value. Therefore, the modulation voltage generator 6B has the following characteristics: u * 、v v * 、v w * Even when the phase and frequency of the first command value v changes transiently, it can quickly generate u * 、v v * 、v w * Synchronous second command value m u 、m v 、m w function.

[0094] Figure 15 It shows Figure 14 The modulation voltage generator 6B includes a three-phase to two-phase converter 601, an amplitude calculator 602, a phase calculator 603, a waveform calculator 604B, and an order amplitude storage device 606B.

[0095] The modulation voltage generator 6B includes a waveform calculator 604B instead of the waveform calculator 604A of the modulation voltage generator 6A in the first embodiment, and includes an order amplitude storage device 606B instead of the waveform storage device 605 .

[0096] The optimized second command value m is stored in advance in the order amplitude storage device 606B. u 、m v 、m w Specifically, in the order amplitude storage device 606B, for the amplitude M, the second command value m is stored. u 、m v 、m w The amplitude m1 of the fundamental component, the amplitude of the sine wave to be included as the higher harmonic component, and the multiple of the frequency of the sine wave to be included as the higher harmonic component relative to the fundamental component. Here, the higher harmonic components have frequencies 3, 5, and 7 times that of the fundamental component, and the amplitudes are set to m3, m5, and m7, respectively. In addition, m1, m3, m5, and m7 are stored in correspondence with the values ​​of amplitude M, with the amplitude of the fundamental component for amplitude M being set to m1(M), and the amplitude of the sine wave for amplitude M being set to m3(M), m5(M), and m7(M). Here, the higher harmonic components when the phase of the sine wave is 180° can be reproduced by making the amplitudes negative.

[0097] In the second embodiment, the same optimization as in the first embodiment is used. Figure 8 The second command value m shown u 、m v 、m w In the first embodiment, four voltage command values ​​for four intervals of a carrier half-cycle are stored to reproduce the waveform of a quarter-cycle of the fundamental component. This has four degrees of freedom, so by using the fundamental component and three frequency harmonic components, the original optimal waveform can be reproduced.

[0098] The waveform calculator 604B calculates the second command value m for the amplitude M. u 、m v 、m w For example, the second command value m for the u-phase of the amplitude M can be calculated using the following formula (7): u (M).

[0099] [Formula 7]

[0100]

[0101] In addition, the second command value m of the three phases u 、m v 、mw The waveform is a waveform in which the phases of the fundamental wave components are mutually shifted by 120°, so the second command value m for the three-phase portion can be generated using the fundamental wave phase θv of the u phase. u 、m v 、m w .

[0102] As described above, according to the power conversion device 1B of the second embodiment, the second command value m u 、m v 、m w Function approximation is performed to reproduce the signal, so the same effects as in Embodiment 1 can be achieved. Specifically, similar to Embodiment 1, the effective value of the load current, i.e., the loss, can be reduced. Furthermore, specific frequency components, such as the fifth and seventh harmonic components, which are expected to cause large noise and torque ripples due to load mechanical resonance, can be reduced and nearly eliminated.

[0103] In the power conversion device 1B according to the second embodiment, the modulation voltage generator 6B sets 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 higher harmonic component, and the multiple of the frequency of the sine wave included in the higher harmonic component relative to the fundamental wave component are stored in the order amplitude storage device 606B as a storage device, and the second command value m is generated using the order amplitude storage device 606B. u 、m v 、m w Therefore, even in the first instruction value v u * 、v v * 、v w * The phase and frequency of the carrier signal c change transiently and the phase synchronization control cannot follow the period, and the first instruction value v u * 、v v * 、v w * Therefore, the voltage supplied to the load can be controlled with high precision and high response.

[0104] Furthermore, the carrier signal generator 7A generates a carrier signal c having a frequency nine times that of the fundamental wave component, and generates a carrier signal c having a frequency nine times that of the fundamental wave component. u 、m v 、m wIn the example, the sine wave of three frequencies is included as the higher harmonic component. u 、m v 、m w In the above, as higher harmonic components, sine waves having frequencies 3 times, 5 times, and 7 times that of the fundamental wave component can be included.

[0105] As described above, according to the power conversion device 1B of the second embodiment, in addition to the effects of the first embodiment, a significant effect of being able to control the voltage supplied to the load with high accuracy and high responsiveness can be achieved.

[0106] Implementation method 3.

[0107] Figure 16 This diagram shows the configuration of a 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 includes a modulation voltage generator 6C in place of the modulation voltage generator 6A of power converter 1A according to Embodiment 1, and includes a carrier signal generator 7B in place of the carrier signal generator 7A. Below, description of portions common to power converter 1A according to Embodiment 1 will be omitted, and the description will focus on portions that differ from power converter 1A.

[0108] Figure 17 It shows Figure 16 1 shows the structure of carrier signal generator 7B. Carrier signal generator 7B includes a three-phase to two-phase converter 701, a phase calculator 702, and a carrier signal calculator 703B. Carrier signal generator 7B includes carrier signal calculator 703B instead of carrier signal calculator 703A of carrier signal generator 7A in Embodiment 1.

[0109] 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, generating a carrier signal c with a frequency 15 times that of the fundamental wave component. Regarding phase synchronization control, the carrier signal generator 7B, like the carrier signal generator 7A, sets the median value of the triangular wave, specifically the phase of the carrier signal c, at 270°, to the first command value v. u * 、v v * 、v w *The phase of the u-phase voltage is synchronized with the phase of the u-phase voltage. In the third embodiment, as in the first embodiment, the carrier signal c is synchronized with the phase of the u-phase voltage, and a 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.

[0110] Figure 18 It shows Figure 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 an order amplitude storage device 606C.

[0111] The modulation voltage generator 6C includes a waveform calculator 604C in place of the waveform calculator 604A of the modulation voltage generator 6A in the first embodiment, and includes an order amplitude storage device 606C in place of the waveform storage device 605 .

[0112] The optimized second command value m is stored in advance in the order amplitude storage device 606C. u 、m v 、m w Specifically, in the order amplitude storage device 606C, for the amplitude M, the second command value m is stored. u 、m v 、m w The amplitude m1 of the fundamental wave component, the amplitude of the sine wave to be included as the higher harmonic component, and the multiple of the frequency of the sine wave to be included as the higher harmonic component relative to the fundamental wave component. Here, the higher harmonic component has six frequencies that are 3 times, 5 times, 7 times, 9 times, 11 times, and 13 times the fundamental wave component, and the amplitudes are set to m3, m5, m7, m9, m10, m110, m120, m130, m140, m150, m160, m170, m180, m200, m210, m220, m230, m240, m250, m260, m270, m280, m290, m300, m310, m320, m330, m340, m350, m360, m400, m410, m50, m50, m60, m70, m80, m90, m110, m120, m130, m140, m150, m 11 、m 13 In addition, m1, m3, m5, m7, m9, m 11 、m 13 The amplitude of the fundamental wave component corresponding to the amplitude M is stored in correspondence with each other, and the amplitude of the sine wave corresponding to the amplitude M is set to m1(M), m3(M), m5(M), m7(M), m9(M), m 11 (M), m 13 (M) Here, the harmonic component when the phase of the sine wave is 180° can be reproduced by making the amplitude a negative value.

[0113] In the carrier half cycle which is a period when the carrier signal c changes from the minimum value to the maximum value or a period when the carrier signal c changes from the maximum value to the minimum value, the second command value m u 、m v 、m wIn addition, it is assumed that the second command value m u 、m v 、m w The waveform is positively and negatively symmetrical between the phases 0° to 180° and 180° to 360°, and is inversely symmetrical between the phases 0° to 90° and 90° to 180°. In the third embodiment, the odd number Kc is set to 15, so the second command value m u 、m v 、m w A quarter cycle of the fundamental wave is equivalent to 7.5 times the half cycle of the carrier wave. However, in order to maintain the symmetry of the phase voltage waveform, the second instruction value m is set to 0.5 in the first 0.5 cycle. u 、m v 、m w Therefore, in this embodiment, only seven values ​​corresponding to seven intervals of the carrier half cycle need to be optimized, which makes optimization easy. u 、m v 、m w The waveform has 7 degrees of freedom, so by using the fundamental component and 6 higher harmonic components, the original optimal waveform can be reproduced.

[0114] In the third embodiment, the objective function f shown in the following formula (8) is obj In a minimization manner, the harmonic components included in the second command value are optimized.

[0115] [Formula 8]

[0116]

[0117] In addition, here, the higher harmonic components are optimized in such a way that the square root of the sum of the squares of the values ​​obtained by dividing the nth-order higher harmonic voltage vn by its order n, that is, the effective value of the load current, becomes the minimum. Here, it is assumed that n = 6i ± 1. Among them, regarding specific frequency components, here, the 11th and 13th-order higher harmonic components, it is assumed that they will excite the mechanical resonance of the load and cause large noise and torque pulsation. By increasing the weighting of these order components, they are preferentially reduced. That is, the weight k in formula (8) is n As shown in the following formula (9), when n is 11 and when n is 13, it is larger than when n is other than 11 and 13. This can reduce load loss while suppressing noise and torque ripple.

[0118] [Formula 9]

[0119]

[0120] In this embodiment, the multiphase inverter circuit 3 and motor 4 have three phases, resulting in three phase waveforms with phases offset by 120°. This prevents the generation of harmonic components that are multiples of three. Furthermore, the voltage waveforms of each phase are positively and negatively symmetrical between phases 0° to 180° and between phases 180° to 360°, preventing the generation of harmonic components that are multiples of two. Furthermore, during optimization, harmonic components up to the 50th order were considered.

[0121] The waveform calculator 604C calculates the amplitude M and the fundamental wave phase θ v , calculate the second instruction value m u 、m v 、m w For example, the second instruction value m of the u phase is calculated using the following formula (10): u (M).

[0122] [Formula 10]

[0123]

[0124] In addition, the second command value m of the three phases u 、m v 、m w The waveforms are mutually phase-shifted by 120°, so the waveform calculator 604C can use the fundamental wave phase θ of the u phase. v To generate the second command value m for the three-phase part u 、m v 、m w .

[0125] Figure 19 The second command value m in the third embodiment is shown. u 、m v 、m w , carrier signal c and output phase voltage v u The waveform of . Figure 19 In FIG. 1 , the case where the amplitude M=0.8 is shown. The second command value m u 、m v 、m w Including the first instruction value v u * 、v v * 、v w * The fundamental wave component and the higher harmonic components including the odd-order sine wave components. Here, the higher harmonic components include the sine wave components whose frequencies are not integer multiples of the number of phases.

[0126] Here, in order to illustrate the effects of the power conversion device 1C according to the present embodiment, a comparative example using a general carrier-synchronized PWM will be described. Figure 20 The phase voltage command value, the carrier signal c, and the output phase voltage v in the comparative example of the third embodiment are shown. u The waveform of . Figure 19 The difference of the third embodiment shown is that the phase voltage command value does not have a high-order harmonic component superimposed thereon. Figure 19 The same signal is shown in the example.

[0127] Here, the effective current value of the motor 4 as a load is evaluated using WTHD represented by the above formula (6). Figure 21 This is a diagram showing the WTHD of a power conversion device 1C according to the third embodiment. Figure 22 This is a diagram showing WTHD in a comparative example of embodiment 3. Figure 21 and Figure 22 In particular, it was confirmed that the WTHD can be significantly reduced in the region where the amplitude M of the modulation voltage is large, and the effective value of the load current, i.e., the loss, can be reduced. However, only in the region where the amplitude M is close to the maximum value, the power conversion device 1C of the third embodiment cannot reduce the WTHD compared with the comparative example. This is because, despite the absence of a change in the second command value m, u 、m v 、m w degrees of freedom, but preferentially reduces the 11th and 13th order harmonic components.

[0128] Furthermore, the harmonic components included in the output phase voltage are compared between the power conversion device 1C according to the third embodiment and the comparative example. Figure 23 1C is a diagram showing the magnitude of harmonic components included in the output phase voltage of the power conversion device 1C according to the third embodiment. Figure 24 : is a diagram showing the magnitude of the higher harmonic components included in the output phase voltage in the comparative example of the third embodiment. Figure 23 as well as Figure 24 In the figure, the horizontal axis is the amplitude M, and the vertical axis is the frequency of the higher harmonics relative to the fundamental wave. Figure 23 as well as Figure 24 In the figure, the magnitude of the higher harmonic components is expressed by the intensity of the colors. ph The value obtained by dividing by half the DC voltage. Figure 23 as well as Figure 24 It can be seen that the power conversion device 1C of the third embodiment can significantly reduce specific frequency components, specifically the 11th and 13th harmonic components, which are expected to cause large noise and torque ripple by exciting mechanical resonance of the load. 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 largely eliminated.

[0129] As described above, according to the power conversion device 1C of the third embodiment, the frequency of the carrier signal c is higher than that of the power conversion device 1A of the first embodiment. However, even in this case, the frequency distribution of the higher harmonics generated by the switching of the multiphase inverter circuit 3 can be optimized with a relatively simple structure. As a result, the power conversion device 1C can achieve the same effects as the first embodiment. In addition, in the third embodiment, the modulation voltage generator 6C stores the amplitude of the fundamental wave component, the amplitude of the sine wave included in the higher harmonic component, and the multiple of the sine wave included in the higher harmonic component relative to the fundamental wave component in the order amplitude storage device 606C, and uses the order amplitude storage device 606C to generate the second command value m. u 、m v 、m w Therefore, similarly to the second embodiment, even if the first command value v u * 、v v * 、v w * The phase and frequency of the carrier signal c change transiently, and the phase synchronization control of the carrier signal c does not completely follow the first instruction value v u * 、v v * 、v w * During the period, it is also possible to u * 、v v * 、v w * The voltage supplied to the motor 4 as a load is thus controlled with high precision and high response. In addition, when the load is the motor 4 as in this embodiment, the speed and torque of the motor 4 can be controlled with high precision and high response.

[0130] Here, the hardware structure of the power conversion devices 1A, 1B, and 1C of embodiments 1 to 3 is described. Here, the power conversion devices 1A, 1B, and 1C are collectively referred to as the power conversion device 1. The functions of the power conversion device 1 can be realized using a processing circuit. Here, the functions of the power conversion device 1 refer to the functions of the modulation voltage generators 6A, 6B, and 6C, the carrier signal generators 7A and 7B, and the selection signal generator 8. The processing circuit can be either Figure 25 Dedicated hardware such as the dedicated processing circuit 14 shown may also be Figure 26 A processor 15 and a storage device 16 are shown.

[0131] Figure 25This diagram illustrates an example configuration of a power conversion device 1 using dedicated hardware. When using dedicated hardware, the dedicated processing circuit 14 may be a single circuit, a composite circuit, a variably programmable processor, a parallel-programmable 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 conversion device 1 described above may be implemented using a separate dedicated processing circuit 14, or the dedicated processing circuit 14 may be used to implement all of the functions of the power conversion device 1.

[0132] Figure 26 This diagram shows an example configuration of a power conversion device 1 using a processor and a storage device. When using a processor 15 and a storage device 16, the various functions of the power conversion device 1 described above are implemented using software, firmware, or a combination thereof. Software and firmware are described as programs, and the processor 15 reads and executes the programs stored in the storage device 16. These programs can also be considered procedures or methods for causing a computer to execute the various functions of the power conversion device 1.

[0133] The processor 15 is a CPU (Central Processing Unit), also known as a processing device, arithmetic device, microprocessor, microcomputer, DSP (Digital Signal Processor), etc. The storage device 16 is, for example, a non-volatile or volatile semiconductor memory such as ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Japanese registered trademark) (Electrically Erasable Programmable Read-Only Memory), a floppy disk, an optical disk, a high-density disk, a DVD (Digital Versatile Disk), etc. Furthermore, some of the multiple functions of the power conversion device 1 may be implemented using dedicated hardware, while others may be implemented using software or firmware.

[0134] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and the embodiments may be combined with each other. Part of the configuration may also be omitted or modified without departing from the spirit of the invention.

[0135] 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 another number of phases, and various inverter circuits such as a multilevel inverter such as a three-level inverter and a five-level inverter can be used.

[0136] In the above embodiment, the carrier signal generators 7A and 7B make the median value of the triangular wave as the carrier signal c and the first command value v u * 、v v * 、v w * In the case of phase 0° synchronization, the median of the rising side of the triangle wave is used. Figure 3 In the example, the phase is 270°. However, the carrier signal generators 7A and 7B may also make the median of the decreasing side of the triangle wave Figure 3 In the example, the phase is 90° and the first command value v u * 、v v * 、v w * The phase is 0° synchronized.

[0137] Furthermore, in the above-described embodiment, the carrier signal generators 7A and 7B generate the common carrier signal c in all phases, but a separate carrier signal c may be prepared for each phase.

[0138] In the above embodiment, the second command value m is set to 0 in the carrier half cycle during which the carrier signal c changes from the minimum value to the maximum value or from the maximum value to the minimum value. u 、m v 、m w However, if a high-speed computing device can be used, a smoother second command value m which is updated with a sufficiently short period relative to the carrier signal c may be used. u 、m v 、m w .

[0139] In the above embodiment, the first command value v u * 、v v * 、v w * Divide by the DC voltage v dc The second command value m of the phase voltage command value for modulation obtained by half of u 、m v 、m w, only the odd-order sine wave components are superimposed on the fundamental wave components, thereby generating a second command value m including the fundamental wave component and a sine wave having an odd-order multiple of the fundamental wave component and at least one higher harmonic component. u 、m v 、m w , and the second instruction value m u 、m v 、m w The waveform of the phase voltage is optimized, but the first command value v u * 、v v * 、v w * , only the odd-order sine wave components are superimposed on the fundamental wave components.

[0140] In addition, in Embodiments 1 and 2, the 5th and 7th harmonic components are preferentially reduced as specific frequency components, while in Embodiment 3, the 11th and 13th harmonic components are preferentially reduced. As described above, when the symmetry of the voltage waveform is taken into account, harmonic components that are integer multiples of the number of phases or even-numbered harmonic components are not generated. Regarding the harmonic components in the case of three phases, when k is an integer, they can be expressed as 6k±1st harmonic components. In addition to the above examples, it is also possible to preferentially reduce components that are freely selected from the 6k±1st harmonic components.

[0141] Explanation of symbols

[0142] 1. 1A, 1B, 1C: power conversion device; 2: DC power supply; 3: multi-phase inverter circuit; 4: motor; 5: motor controller; 6A, 6B, 6C: modulation voltage generator; 7A, 7B: carrier signal generator; 8: selection signal generator; 14: dedicated processing circuit; 15: processor; 16: storage device; 31, 31u, 31v, 31w: branch; 601, 701: three-phase to two-phase converter; 602: amplitude operator; 603, 702: phase operator; 604A, 604B, 604C: waveform operator; 605: waveform storage device; 606B, 606C: frequency amplitude storage device; 703A, 703B: carrier signal operator.

Claims

1. A power conversion device for supplying power to a multi-phase load based on a first command value that is a sinusoidal phase voltage command value, characterized in that: The power conversion device comprises: A multiphase inverter circuit is configured such that a number of branches, each consisting of two semiconductor switching elements having a reverse conducting function connected in series, are connected in parallel between the positive and negative terminals of a DC power supply, the same number as the number of phases, and a terminal between two of the semiconductor switching elements in each of the plurality of branches is connected to each phase of the load. a modulation voltage generator for generating a second command value as a phase voltage command value for modulation, the second command value including a fundamental wave component of the first command value and a higher harmonic component, the higher harmonic component including at least one sine wave having a frequency that is an odd multiple of the fundamental wave component; a carrier signal generator for generating the triangular wave carrier signal so that the frequency is an odd multiple of the fundamental wave component of the first command value and the median of the triangular wave is synchronized with the phase zero of the fundamental wave component of the first command value; as well as A gate signal generator generates a gate signal for driving the semiconductor switch element based on a comparison result between the second command value and the carrier signal.

2. The power conversion device according to claim 1, wherein: The higher harmonic components included in the second command value include at least one sine wave having a frequency that is an odd multiple of the fundamental wave component of the first command value and that is not an integral multiple of the number of phases of the multi-phase inverter circuit.

3. The power conversion device according to claim 1 or 2, characterized in that: The modulation voltage generator stores the second command value corresponding to a quarter cycle of the fundamental wave component of the first command value in a storage device, and generates the second command value using the storage device.

4. The power conversion device according to claim 1 or 2, characterized in that: The modulation voltage generator stores the amplitude of the fundamental component, the amplitude of the sine wave included in the higher harmonic component, and the multiple of the frequency of the sine wave included in the higher harmonic component relative to the fundamental component in a storage device, and uses the storage device to generate the second command value.

5. The power conversion device according to any one of claims 1 to 4, characterized in that: The carrier signal generator generates the carrier signal having a frequency nine times that of the fundamental wave component. The higher harmonic components include sine waves of three frequencies.

6. The power conversion device according to claim 5, characterized in that The higher harmonic components include sine waves having frequencies three times, five times, and seven times that of the fundamental wave component.

7. The power conversion device according to any one of claims 1 to 4, characterized in that: The carrier signal generator generates the carrier signal having a frequency 15 times that of the fundamental wave component. The high-order harmonic components include sine waves of 6 frequencies.

8. The power conversion device according to claim 7, characterized in that The higher harmonic components include sine waves having frequencies 3 times, 5 times, 7 times, 9 times, 11 times, and 13 times that of the fundamental wave component.

9. The power conversion device according to any one of claims 1 to 8, characterized in that: A multiple of the frequency of the carrier signal relative to the fundamental wave component is an odd number and an integer multiple of the number of phases of the multi-phase inverter circuit.

10. The power conversion device according to any one of claims 1 to 9, characterized in that: The modulation voltage generator maintains the second command value at a constant value in a carrier half cycle, which is a period during which the carrier signal changes from a minimum value to a maximum value or a period during which the carrier signal changes from a maximum value to a minimum value.

11. The power conversion device according to any one of claims 1 to 10, characterized in that: Compared to a case where the second command value does not include the harmonic component, the effective value of the current of the load is lower.

12. The power conversion device according to any one of claims 1 to 10, characterized in that: Compared to a case where the second command value does not include the harmonic component, the amplitude of the predetermined frequency component included in the phase voltage of the load is lower.

13. A control method for a power conversion device, the power conversion device comprising a multiphase inverter circuit, wherein a number of branches, each consisting of two semiconductor switching elements having a reverse conduction function connected in series, equal to the number of phases, are connected in parallel between the positive and negative terminals of a DC power supply, and a terminal between two of the semiconductor switching elements in each of the plurality of branches is connected to a respective phase of a load. The power conversion device supplies power to the multiphase load in accordance with a first command value, which is a sinusoidal phase voltage command value. The control method comprises: generating a second command value as a phase voltage command value for modulation, wherein the second command value includes a fundamental wave component of the first command value and a higher harmonic component, the higher harmonic component including at least one sine wave having an odd-integer frequency relative to the fundamental wave component; generating a carrier signal of the triangular wave such that the frequency is an odd multiple of the fundamental wave component of the first command value and the median of the triangular wave is synchronized with the phase zero of the fundamental wave component of the first command value; and A step of generating a gate signal for driving the semiconductor switch element based on a comparison result between the second command value and the carrier signal.

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