Power conversion device

Abstract

A power conversion device (100) is provided with: a rectifying unit (2) for converting a three-phase AC voltage into a DC voltage; a power converter (6) that converts a DC voltage into an AC voltage and controls the electric motor (7); and a control unit (50) that derives, on the basis of a detected value of a three-phase AC voltage, a ripple included in a DC voltage obtained by full-wave rectification of the three-phase AC voltage as a ripple voltage predicted value ([Delta] Vdc *), and derives, on the basis of a detected value of the DC voltage, a ripple included in the DC voltage as a ripple voltage measured value ([Delta] Vdc). At least one of the D-axis voltage command (Vd *) and the Q-axis voltage command (Vq *) is corrected by voltage correction commands ([delta] Vd *, [delta] Vq *) generated so as to reduce the deviation between the ripple voltage predicted value ([delta] Vdc *) and the ripple voltage measured value ([delta] Vdc).

Description

Technical Field

[0001] The present application relates to a power conversion device. Background Art

[0002] As a power conversion device for driving an AC motor, a power conversion device composed of a rectifier that rectifies AC power input from a three-phase AC power source such as a commercial power source into DC power and an inverter that converts the DC power into AC power suitable for the AC motor and outputs it to the AC motor is used. Generally speaking, it is known that if a three-phase AC voltage is rectified by a rectifier composed of diodes, pulsation with a frequency six times the frequency of the AC power source is generated in the rectified DC voltage.

[0003] Here, a smoothing capacitor is provided in a DC link portion connecting the DC output side of a rectifier and the DC input side of an inverter, and an LC resonance circuit is formed by the inductance component on the AC power supply side and the smoothing capacitor. When the resonance frequency of the LC resonance circuit coincides with a frequency six times the power supply frequency, the DC voltage of the DC link portion pulsates greatly. In particular, when a small-capacity film capacitor is used as a smoothing capacitor for the purpose of miniaturization of the device, a large pulsation of the DC voltage and distortion of the power supply current often occur, and sometimes the continuous operation of the power conversion device becomes difficult. In order to solve such a problem, an inverter device as a power conversion device having the following structure is disclosed.

[0004] That is, the conventional inverter device includes an inductor connected between a diode bridge as a rectifier and an inverter unit, and a capacitor connected to an input terminal of the inverter unit. The control unit of the inverter unit multiplies the voltage across the inductor detected by the voltage detector by a gain (k). The voltage across the inductor multiplied by the gain (k) is subtracted from the signal from the PI controller or the initial value of the voltage control rate (for example, refer to Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2008-29151 (FIG. 18, FIG. 19) Summary of the invention

[0008] Problems to be solved by the invention

[0009] In the conventional inverter device as described above, the voltage across the inductor provided between the diode bridge and the smoothing capacitor is detected and multiplied by a gain (k), and then the current command as a signal from the PI controller or the modulation rate as a voltage control rate is corrected. This can improve the ripple of the power supply current and the DC voltage.

[0010] However, in such a correction method based on the detected value of the voltage across the inductor, the greater the impedance on the power supply side, the smaller the effect of the control to suppress the pulsation. In addition, for the correction of the current command, it is difficult to improve the pulsation unless the current control system is designed to have a very high response. In addition, on the DC link voltage, in addition to the pulsation of 6 times the power supply frequency, there is also superimposed a high-order pulsation of more than 6 times due to the rectification action of the rectifier, the resonance of the LC resonant circuit, etc. In the above-mentioned conventional correction method, there is a problem that the effect of suppressing such pulsation is small, and the effect of suppressing the distortion of the power supply current is also small.

[0011] The present application discloses a technology for solving the above-mentioned problems, and an object of the present application is to provide a power conversion device capable of effectively suppressing ripple generated in a power supply current or a DC link unit.

[0012] Solutions to Solve Problems

[0013] The power conversion device disclosed in the present application comprises:

[0014] A rectifier unit, which converts the input three-phase AC voltage into a DC voltage and outputs it to a DC bus;

[0015] a power converter that converts the DC voltage in the DC bus converted by the rectifier into an AC voltage to control the motor; and

[0016] a control unit that controls the power converter,

[0017] The control unit is configured as follows:

[0018] converting the current flowing in the motor into a D-axis current and a Q-axis current on orthogonal two-axis coordinates, generating a D-axis voltage command so that the D-axis current follows the D-axis current command, and generating a Q-axis voltage command so that the Q-axis current follows the Q-axis current command, and controlling the power converter based on the generated D-axis voltage command and the generated Q-axis voltage command,

[0019] Based on the detected value of the three-phase AC voltage, the pulsation contained in the DC voltage obtained by full-wave rectification of the three-phase AC voltage is derived as a pulsation voltage prediction value, and based on the detected value of the DC voltage, the pulsation contained in the DC voltage is derived as a pulsation voltage actual value,

[0020] At least one of the D-axis voltage command and the Q-axis voltage command is corrected by a voltage correction command generated so as to reduce a deviation between the pulsating voltage prediction value and the pulsating voltage actual measurement value.

[0021] Effects of the Invention

[0022] According to the power conversion device disclosed in the present application, it is possible to effectively suppress ripples generated in the power supply current and the DC link unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a block diagram showing a schematic configuration of a power conversion device according to the first embodiment.

[0024] Figure 2 This is a control block diagram showing the internal structure of the control unit of the power conversion device according to the first embodiment.

[0025] Figure 3 This is a control block diagram showing the configuration of the pulsation suppression control unit of the power conversion device according to the first embodiment.

[0026] Figure 4 This is a diagram showing an example of the hardware configuration of a control unit as a control device according to the first embodiment.

[0027] Figure 5A , Figure 5B It is a diagram showing an operation waveform of a power conversion device according to a comparative example.

[0028] Fig. 6A , Figure 6B It is a diagram showing an operation waveform of the power conversion device according to the first embodiment.

[0029] Fig. 7A , Figure 7B It is a diagram showing an operation waveform of the power conversion device according to the first embodiment.

[0030] Figure 8 This is a control block diagram showing the internal structure of the pulsation suppression control unit of the power conversion device according to the second embodiment.

[0031] Fig. 9 This is a control block diagram showing the internal structure of the pulsation suppression control unit of the power conversion device according to the second embodiment. DETAILED DESCRIPTION

[0032] Implementation Method 1

[0033] The power conversion device 100 according to the first embodiment will be described with reference to the drawings.

[0034] Figure 1 This is a block diagram showing a schematic configuration of the power conversion device 100 according to the first embodiment.

[0035] The power conversion device 100 is provided between a three-phase AC power source 1 such as a commercial power source and a motor 7 as an electric motor, temporarily converts AC power from the AC power source 1 into DC power, and converts the converted DC power into AC power to supply the motor 7 as a load.

[0036] The power conversion device 100 includes a rectifier 2 as a rectifying unit, a DC link unit 5 , an inverter 6 as a power converter, and a control unit 50 .

[0037] The rectifier 2 is composed of diodes, and performs full-wave rectification on a three-phase AC voltage input from a three-phase AC power source 1 to convert the voltage into a DC voltage.

[0038] The DC link unit 5 is provided between the rectifier 2 and the inverter 6, and supplies the DC power converted by the rectifier 2 to the inverter 6. The DC link unit 5 includes: positive and negative DC bus lines P and N connecting the DC output side of the rectifier 2 and the DC input side of the inverter 6; a DC reactor 3 connected in series with the positive DC bus line P; and a smoothing capacitor 4 provided between the positive and negative DC bus lines P and N.

[0039] The inverter 6 includes six semiconductor elements (not shown), which are driven by a drive signal G from the control unit 50 to convert the DC voltage from the DC link unit 5 into an AC voltage with a variable voltage and frequency, thereby controlling the motor 7 at an arbitrary rotation speed.

[0040] In addition, the power conversion device 100 also has: a voltage sensor 10 for detecting the line voltage Vab of the AC voltage on the AC power supply 1 side; a voltage sensor 11 for detecting the DC bus voltage Vdc between the DC buses P and N; and a load current sensor 12 for detecting the load currents Iu, Iv, and Iw flowing in each phase of the motor 7.

[0041] The input to the control unit 50 is characterized in that, in addition to the information of the DC bus voltage Vdc, the information of the load currents Iu, Iv, and Iw flowing in the motor 7, and the information of the angular velocity ω of the motor 7, the information of the line voltage Vab on the AC power supply 1 side detected by the voltage sensor 10 for suppressing the pulsation generated in the AC power supply 1 and the DC link unit 5 is also input, and the details will be described later. The control unit 50 generates a drive signal G for controlling the inverter 6 based on these input detection values.

[0042] In addition, although the load current sensor 12 is shown to obtain all currents of the three-phase load currents Iu, Iv, and Iw, the current of the remaining phase can be calculated by detecting the currents of two phases among the three phases, so only two phases may be actually detected. As another method, a current sensor may be provided on the input negative electrode side of the semiconductor element of the inverter 6, and multiple sampling may be performed to calculate the three-phase currents respectively.

[0043] Furthermore, in order to reduce higher harmonic noise, a DC reactor 3 is generally inserted into the DC bus P. However, in the power conversion device 100 of the present embodiment, the DC reactor 3 is not necessarily required, and therefore the DC reactor 3 can be eliminated.

[0044] Next, the control unit 50 will be described.

[0045] Figure 2 1 is a control block diagram showing the internal structure of the control unit 50 of the power conversion device 100 according to Embodiment 1. In this embodiment, a control block for performing vector control is adopted.

[0046] The control unit 50 includes: PI control units 22, 23, 24 for performing feedback control based on input deviations; a coordinate conversion unit 25 for converting two-phase D-axis voltage instructions Vd* and Q-axis voltage instructions Vq* into three-phase voltage instructions Vu*, Vv*, Vw*; a PWM control unit 26 for generating a drive signal G for driving a semiconductor element of the inverter 6 based on the converted voltage instructions Vu*, Vv*, Vw*; a pulsation suppression control unit 30 for suppressing pulsation in the power supply current and the DC link unit 5; and subtractors 21A, 21B, 21C, 21D, 21E.

[0047] In the control unit 50 , the detected load currents Iu, Iv, and Iw of the motor 7 are converted into a D-axis current Id and a Q-axis current Iq on orthogonal biaxial coordinates by a converter (not shown).

[0048] Then, the subtractor 21A calculates the deviation between the angular velocity command ω* as the velocity command and the angular velocity ω estimated by the position sensorless control, and the PI control unit 22 performs PI control to reduce the calculated deviation, thereby deriving the Q-axis current command Iq*.

[0049] The subtractor 21B calculates the deviation between the Q-axis current command Iq* and the detected Q-axis current Iq, and the PI control unit 23 performs PI control to calculate the Q-axis voltage command Vq* so as to reduce the calculated deviation, that is, so as to make the Q-axis current Iq follow the Q-axis current command Iq*.

[0050] Similarly for the D axis, the deviation between the D axis current command Id* and the detected D axis current Id is calculated by the subtractor 21D, and the PI control is performed by the PI control unit 24 in such a way as to reduce the calculated deviation, that is, in such a way that the D axis current Id follows the D axis current command Id*, and the D axis voltage command Vd* is calculated.

[0051] Furthermore, the pulsation suppression control unit 30 calculates a D-axis voltage correction command ΔVd* as a voltage correction command and a Q-axis voltage correction command ΔVq* as a voltage correction command. The pulsation suppression control unit 30 will be described in detail later.

[0052] Then, the D-axis voltage command Vd* is corrected by subtracting the D-axis voltage correction command ΔVd* from the D-axis voltage command Vd* by the subtractor 21E. In addition, the Q-axis voltage command Vq* is corrected by subtracting the Q-axis voltage correction command ΔVq* from the Q-axis voltage command Vq* by the subtractor 21C. The corrected D-axis voltage command Vd* and Q-axis voltage command Vq* are input to the coordinate conversion unit 25.

[0053] The coordinate conversion unit 25 performs coordinate conversion from D and Q axis rotating coordinates to stationary coordinates of U, V and W, which are actual output voltage commands. The voltage commands Vu*, Vv* and Vw* of each phase obtained by the coordinate conversion are input to the PWM control unit 26 .

[0054] The PWM control unit 26 generates a drive signal G for the semiconductor element of the inverter 6 based on the input voltage commands Vu*, Vv*, and Vw* of the respective phases.

[0055] In addition, since the coordinate conversion unit 25 and the PWM control unit 26 are methods used in general inverter control, detailed descriptions thereof are omitted here.

[0056] In addition, although the control block described here does not record the decoupling control of the DQ axes for suppressing the interference of the DQ axes, the decoupling control of the DQ axes can also be performed before the voltage command is corrected by the D-axis voltage correction command ΔVd* and the Q-axis voltage correction command ΔVq* from the pulsation suppression control unit 30.

[0057] Next, the pulsation suppression control unit 30 which is a main part of the power conversion device 100 according to the present embodiment will be described in detail.

[0058] Figure 3 1 is a control block diagram showing the configuration of the pulsation suppression control unit 30 of the power conversion device 100 according to the first embodiment.

[0059] The ripple suppression control unit 30 performs ripple suppression control for suppressing voltage ripple and current distortion generated from the AC power supply 1 to the DC link unit 5 .

[0060] The pulsation suppression control unit 30 includes an amplitude / phase calculation unit 31 , a pulsating voltage command calculation unit 32 , a D-axis feedback control unit 35 that performs feedback control based on an input deviation, a Q-axis feedback control unit 36 ​​, gain adjustment units 37 , 38 , and high-pass filters 33A, 33B.

[0061] The inputs of the pulsation suppression control unit 30 are the detected line voltage Vab on the AC power supply 1 side and the detected DC bus voltage Vdc. The outputs of the pulsation suppression control unit 30 are the D-axis voltage correction command ΔVd* and the Q-axis voltage correction command ΔVq*.

[0062] Hereinafter, the ripple suppression control performed by the ripple suppression control unit 30 will be described in order from the input of the line voltage Vab.

[0063] First, in the amplitude / phase calculation unit 31, the amplitude Vs and the phase θs are calculated based on the simulated voltage signal. As a calculation method, the method of ePLL (enhanced phase looked loop) can be used. In addition, the amplitude Vs and the phase θs of the AC voltage can also be derived using the zero-crossing signal of the line voltage Vab. If only the zero-crossing from negative to positive is detected, the zero-crossing signal is input once in one cycle of the power supply. The time T1 between zero-crossing-zero-crossing and the time T2 between zero-crossing-zero-crossing in the previous cycle can be used to calculate the phase angle as shown in the following formula (1). The unit is set to radians [rad].

[0064]

Mathematical formula 1

[0065] θ=T1 / T2*2π…(1)

[0066] The amplitude Vs can be calculated as shown in the following equation (2) by integrating the absolute value of the power line voltage Vab between zero crosses and zero crosses and taking the average value.

[0067]

Mathematical formula 2

[0068]

[0069] In the equation (2), π / 2 is a coefficient for converting the average value into an effective value. By using the above equations (1) and (2) based on the zero-cross signal, the amplitude Vs and the phase θs can be derived.

[0070] Even without detecting the line voltage Vab by simulation, the amplitude Vs and the phase θs can be calculated only from the zero-crossing signal. In this case, the amplitude Vs can be derived by the following equation (3) using the average value Vdcave of the DC bus voltage.

[0071]

Mathematical formula 3

[0072] V s =K1V dcave …(3)

[0073] K1 is the gain, and is usually set to "K1 = π / 3". If the resistance component such as the power supply impedance is large, K1 can be slightly increased to make fine adjustments.

[0074] The amplitude Vs and the phase θs of the AC voltage calculated by the amplitude / phase calculation unit 31 are input to the pulsating voltage command calculation unit 32 .

[0075] The pulsating voltage command calculation unit 32 can restore the phase voltages Va, Vb, and Vc of the three-phase AC power source 1 respectively as shown in the following equations (4) to (6) using the input amplitude Vs and phase θs.

[0076]

Mathematical formula 4

[0077]

[0078]

Mathematical formula 5

[0079]

[0080]

Mathematical formula 6

[0081]

[0082] Then, for the restored three-phase AC power supply 1 phase voltages Va, Vb, Vc, the minimum phase voltage Va, Vb, Vc is subtracted from the maximum phase voltage Va, Vb, Vc in each phase, thereby deriving the DC bus voltage prediction value Vdc*. When expressed in mathematical form, equation (7) is obtained.

[0083]

Mathematical formula 7

[0084]

[0085] Then, the DC component of the DC bus voltage prediction value Vdc* is removed by the high-pass filter 33A, so that the pulsating voltage prediction value ΔVdc* from which the AC component is extracted can be calculated.

[0086] The pulsating voltage prediction value ΔVdc* is a prediction value of an AC component included in a DC bus voltage between DC buses P and N obtained by full-wave rectifying a three-phase AC voltage, and is a pulsation oscillating at a frequency six times the frequency of the AC voltage of the AC power supply 1 .

[0087] Below, from Figure 3The following description will be given starting from the DC bus voltage Vdc input at the lower side of the figure.

[0088] The DC bus voltage Vdc detected by the voltage sensor 11 is subjected to a high-pass filter 33B to remove the DC component, thereby deriving a pulsating voltage actual measurement value ΔVdc obtained by extracting the actual AC component on the DC buses P and N.

[0089] The high-pass filters 33A and 33B are provided because if the pulsating voltage prediction value ΔVdc* and the pulsating voltage actual measurement value ΔVdc to be derived have a residual DC component, they will be Figure 2 The motor control itself may not work well due to the current control disturbance shown. Therefore, the insertion of high pass filters 33A, 33B is necessary.

[0090] Then, the pulsating voltage actual measurement value ΔVdc is subtracted from the pulsating voltage prediction value ΔVdc* by a subtractor 34 to obtain a deviation ΔVerr.

[0091] Here, the actual measured value of the pulsation in the DC link unit 5, that is, the pulsating voltage measured value ΔVdc, has a higher wave height than the pulsating voltage predicted value ΔVdc* that oscillates at a frequency six times the power supply frequency predicted by calculation. In addition, the pulsating voltage measured value ΔVdc is a waveform that also includes high-order pulsations having a frequency exceeding six times the power supply frequency due to the actual rectification operation of the rectifier 2, the resonance of the LC resonance circuit formed in the actual circuit, and the like. Therefore, the deviation ΔVerr derived by subtracting the pulsating voltage measured value ΔVdc from the pulsating voltage predicted value ΔVdc* is a waveform that includes the sixth-order pulsations and the higher-order pulsations exceeding the sixth-order.

[0092] Then, the D-axis feedback control unit 35 performs feedback control on the D-axis to derive a control amount 35C so as to reduce the deviation ΔVerr, that is, so as to reduce pulsations including 6th-order pulsations and higher-order pulsations exceeding 6th-order pulsations.

[0093] Then, in the gain adjustment unit 37 , the control amount 35C is multiplied by a gain 37G (Vdc / Id) as a first gain that is proportional to the DC bus voltage Vdc and inversely proportional to the D-axis current Id, thereby calculating a D-axis voltage correction command ΔVd*.

[0094] Proportional (P) control is usually used for feedback control. However, when the control bandwidth is increased, proportional derivative (PD) control may also be used.

[0095] The P control can be expressed by the following equation (8), and the PD control can be expressed by the following equation (9).

[0096]

Mathematical formula 8

[0097] G(s)=K P ...(8)

[0098]

Mathematical formula 9

[0099] G(s)=K P +K d S…(9)

[0100] In the above equations (8) and (9), Kp is a proportional gain as a control gain, and Kd is a differential gain as a control gain. Instead of performing PD control, a configuration may be adopted in which phase advance control and P control are performed by a phase advance compensation filter. The phase advance control is a control that makes the control amount derived by P control advance by a set phase amount, and by compensating for control lag generated by a control cycle that performs feedback control, the pulsation suppression effect can be improved.

[0101] Similarly for the Q axis, the feedback control unit 36 ​​performs feedback control and calculates the control amount 36C so as to reduce the deviation ΔVerr, that is, so as to reduce pulsations including 6th-order pulsations and higher-order pulsations exceeding 6th-order pulsations.

[0102] Then, in the gain adjustment unit 38 , the control amount 36C is multiplied by a gain 38G (Vdc / Iq) as a first gain that is proportional to the DC bus voltage Vdc and inversely proportional to the Q-axis current Iq, thereby calculating a Q-axis voltage correction command ΔVq*.

[0103] Such D-axis voltage correction command ΔVd* and Q-axis voltage correction command ΔVq* perform corrections to increase the D-axis voltage and the Q-axis voltage in order to increase the output power of the inverter 6 when the DC bus voltage Vdc increases. In addition, the D-axis voltage correction command ΔVd* and the Q-axis voltage correction command ΔVq* perform corrections to decrease the D-axis voltage and the Q-axis voltage in order to decrease the output power of the inverter 6 when the DC bus voltage Vdc decreases. In this way, pulsation suppression control is performed to suppress pulsation in the power supply current and the DC link unit 5.

[0104] Furthermore, the magnitudes of the control amounts 35C and 36C in the present embodiment are adjusted by the gains 37G and 38G serving as the first gains, respectively.

[0105] Such gains 37G and 38G have the effect of making the control effect by the pulsation suppression control constant. The gain 37G will be described below as an example.

[0106] First, the output power of the inverter 6 is set to Pout+ΔPout. The DC component of the output power is Pout, and the pulsating power of the output power is ΔPout. Pout is the DC power generated by normal motor control, and ΔPout is the pulsating power generated to suppress resonance. The output power Pout+ΔPout can be calculated by the following formula (10).

[0107]

Mathematical formula 10

[0108] P out +ΔP out =(V d +ΔV d )(I d +ΔI d )+(V q +ΔV q )(I q +ΔI q )=(V d I d +V d ΔI d +ΔV d I d +ΔV d ΔI d )+(V q I q +V q ΔI q +ΔV q I q +ΔV q ΔI q )…(10)

[0109] Among them, Vd is the DC component of the D-axis voltage, ΔVd is the AC component of the D-axis voltage, Vq is the DC component of the Q-axis voltage, ΔVq is the AC component of the Q-axis voltage, Id is the DC component of the D-axis current, ΔId is the AC component of the D-axis current, Iq is the DC component of the Q-axis current, and ΔIq is the AC component of the Q-axis current.

[0110] Here, if the DC component power Pout is represented, equation (11) is obtained.

[0111]

Mathematical formula 11

[0112] P out =V d I d +V q I q ...(11)

[0113] ΔPout can be derived from equations (10) and (11) to obtain equation (12).

[0114]

Mathematical formula 12

[0115] ΔP out =(V d ΔI d +ΔV d I d +ΔV d ΔI d )+(V q ΔI q +ΔV q I q +ΔVqΔI q )…(12)

[0116] In this equation (12), the term ΔV*I, which is the product of the voltage AC component ΔV and the current DC component I, plays a leading role. Due to the characteristics of the motor, even if ΔV changes, ΔI does not change significantly, so it can be approximated by ignoring the term ΔI. If the approximation is performed, equation (13) is obtained.

[0117]

Mathematical formula 13

[0118]

[0119] Next, the input current of the inverter 6 is calculated. If the input power of the inverter 6 is set to Pin+ΔPin, it can be expressed by the following equation (14).

[0120]

Mathematical formula 14

[0121] P in +ΔP in =(V dc +ΔV dc )(I dc +ΔI dc )=(V dc I dc +V dc ΔI dc +ΔV dc I dc +ΔV dc ΔI dc )…(14)

[0122] Wherein, Vdc is the DC voltage component of the DC bus voltage, ΔVdc is the AC component of the DC bus voltage, Idc is the DC component of the inverter input current, and ΔIdc is the AC component of the inverter input current.

[0123] Here, if the DC component power Pin is represented, the following equation (15) is obtained.

[0124]

Mathematical formula 15

[0125] P in =V dc I dc …(15)

[0126] ΔPin can be derived from equations (14) and (15) to obtain the following equation (16).

[0127]

Mathematical formula 16

[0128] ΔP in =V dc ΔI dc +ΔV dc I dc +ΔV dc ΔI dc …(16)

[0129] Here, if inverter 6 is appropriately controlled, the term ΔVdc of the oscillation component of the bus voltage becomes small, and the term Vdc*ΔIdc becomes dominant. Therefore, when approximation is performed, the following equation (17) is obtained.

[0130]

Mathematical formula 17

[0131]

[0132] If ΔIdc is placed on the left and arranged, it can be expressed by equation (18).

[0133]

Mathematical formula 18

[0134]

[0135] Since ΔPin and ΔPout are equal, by substituting equation (13) into ΔPin of equation (18), equation (19) can be derived.

[0136]

Mathematical formula 19

[0137] ΔI dc =I d / V dc ΔV d +I q / V dc ΔV q …(19)

[0138] According to the result of formula (19), when the pulsating voltage ΔVd is intentionally given to the D-axis in order to suppress resonance, a pulsating input current ΔIdc proportional to the D-axis current Id and inversely proportional to the DC bus voltage Vdc is obtained relative to the given pulsating voltage ΔVd. Therefore, it can be seen that if Id and Vdc change, the control amount of ΔIdc will also change.

[0139] Therefore, in order to make ΔIdc constant, in the case of the D axis, the control amount 35C that gives the pulsating voltage to the D axis voltage command Vd* may be multiplied by the gain 37G in such a manner as the gain 37G, so as to be proportional to the DC bus voltage Vdc and inversely proportional to the D axis current Id. Similarly, in the case of the Q axis, the control amount 36C that gives the pulsating voltage to the Q axis voltage command Vq* may be multiplied by the gain 38G in such a manner as the gain 38G, so as to be proportional to the DC bus voltage Vdc and inversely proportional to the Q axis current Iq.

[0140] The values ​​of the DC bus voltage Vdc, the D-axis current Id, and the Q-axis current Iq used in the gains 37G and 38G may use the average values ​​when the motor 7 is driven, but are not limited to this. For example, the gains 37G and 38G may not be preset fixed values, but may adopt a structure in which the values ​​of the gains 37G and 38G are updated according to the detected values ​​of the DC bus voltage Vdc, the D-axis current Id, and the Q-axis current Iq when the motor 7 is driven.

[0141] Gain 37G adjusts the control amount in feedback control to be proportional to the detected DC bus voltage Vdc and inversely proportional to the D-axis current Id. By adjusting the control amount in this way, even if Vdc and Id change, the control amount of ΔIdc can be kept constant, and the control effect can be further kept constant. Therefore, the deviation of the control effect such as insufficient control amount and generation of pulsation depending on the conditions can be suppressed, and resonance can be suppressed more efficiently.

[0142] In addition, the structure in which the gain 37G is inversely proportional to the D-axis current Id and the gain 38G is inversely proportional to the Q-axis current Iq is shown, but it is not limited to this. As shown in the above formula (19), as long as the gains 37G and 38G are both at least proportional to the DC bus voltage Vdc, even if they are not inversely proportional to the D-axis current Id and the Q-axis current Iq, the effect of making ΔIdc constant to a certain extent can be obtained.

[0143] Alternatively, only one of the D-axis voltage command Vd* and the Q-axis voltage command Vq* may be corrected by the voltage correction command. In this case, when the D-axis voltage command Vd* does not need to be corrected, control may be performed to disable the D-axis voltage correction command ΔVd*.

[0144] In addition, when performing field weakening control or the like, in the case of an operation in which a current flows in the D axis in addition to the Q axis current, the D axis voltage command Vd* and the Q axis voltage command Vq* can be corrected by the voltage correction command. Thus, even when the motor 7 rotates at a high speed, resonance can be suppressed, and healthy operation of the motor 7 within a wide speed range can be ensured.

[0145] Next, the hardware configuration of the control unit 50 will be described.

[0146] As described below using the accompanying drawings, the control unit 50 generally executes the above Figure 2 , Figure 3 The control block shown is composed of a microcomputer, etc.

[0147] Figure 4 This is a diagram showing an example of the hardware configuration of the control unit 50 as the control device according to the first embodiment.

[0148] like Figure 3 As an example of hardware shown in FIG. 1 , the control device is composed of a processor 51 and a storage device 52. The storage device 52 includes a volatile storage device such as a random access memory (not shown) and a nonvolatile auxiliary storage device such as a flash memory.

[0149] In addition, an auxiliary storage device including a hard disk may be used instead of the flash memory. The processor 51 executes the program input from the storage device 52. In this case, the program is input from the auxiliary storage device to the processor 51 via the volatile storage device. In addition, the processor 51 may output data such as the calculation result to the volatile storage device of the storage device 52, or may store the data in the auxiliary storage device via the volatile storage device.

[0150] Hereinafter, the effectiveness of the pulsation suppression control will be confirmed by using the actual operation waveforms using the attached drawings.

[0151] Figure 5A and Figure 5B It is a diagram showing an operation waveform of a power conversion device according to a comparative example in which pulsation suppression control is not performed.

[0152] Figure 5A The power supply current waveform is shown when the power supply operates with a low torque load of Id = 0A and Iq = 30A. Figure 5B The power supply current waveform when operating with a high torque load of Id=0A and Iq=100A is shown.

[0153] Since large pulsations were generated in both cases, it was confirmed that resonance occurred.

[0154] Fig. 6A and Figure 6B 1 is a diagram showing operation waveforms of the power conversion device 100 according to the present embodiment when performing pulsation suppression control.

[0155] Fig. 6A The power supply current waveform when operating with a low torque load of Id=0A and Iq=30A is shown. Figure 6B The power supply current waveform when operating with a high torque load of Id=0A and Iq=100A is shown.

[0156] The feedback control in the pulsation suppression control unit 30 is set to only P control, and the Q-axis feedback gain is set to Kp = 0.3. For the D-axis, since Id = 0A, even if compensation is performed, there is little effect, so in the case of this waveform, no feedback is performed. That is, in the case of this waveform, the power conversion device 100 corrects only the Q-axis voltage command Vq* by the Q-axis voltage correction command ΔVq*.

[0157] If you observe Fig. 6A , Figure 6B Both waveforms can significantly reduce pulsation, confirming the effect of pulsation suppression control.

[0158] Fig. 7A and Figure 7B These are the operating waveforms when gains of 37G and 38G are applied at fixed values.

[0159] Fig. 7A The power supply current waveform is shown in the case of low torque load operation with Id = 0A and Iq = 30A. Fig. 6A When the gain is adjusted in the same waveform, if the load is operated with a high torque of Id = 0A and Iq = 100A, the Figure 7B In the waveform diagram, the power supply current waveform oscillates.

[0160] Therefore, it can be confirmed that the gains 37G and 38G are important structures for realizing stable operation under various operating conditions.

[0161] The gain 37G is divided by the D-axis current Id, so when the value of the D-axis current Id is small, the D-axis voltage correction command ΔVd* becomes too large. In this case, the clamp control described below is performed to prevent the value of the D-axis current Id from being too small, or the control of disabling the D-axis voltage correction command ΔVd* is performed when the D-axis current Id is 0 or infinitely small. The same is true for the Q-axis current Iq of the gain 38G.

[0162] When clamp control is performed, for example, if the D-axis current Id or the Q-axis current Iq reaches a value within the set first value range, the value of the D-axis current Id for the gain 37G and the value of the Q-axis current Iq for the gain 38G may be adjusted to a value exceeding the first value range. For example, if the first value range is set to a range of -10 to +10, clamp control is performed so that when the D-axis current Id is -2, the value is clamped to -10.1, and when the Q-axis current Iq is +3, the value is clamped to +10.1.

[0163] In particular, when the motor 7 rotates at a low or medium speed, control is often performed at Id of 0 A, which corresponds to this phenomenon.

[0164] The power conversion device of the present embodiment configured as described above includes:

[0165] A rectifier unit, which converts the input three-phase AC voltage into a DC voltage and outputs it to a DC bus;

[0166] a power converter that converts the DC voltage in the DC bus converted by the rectifier into an AC voltage to control the motor; and

[0167] a control unit that controls the power converter,

[0168] The control unit is configured as follows:

[0169] converting the current flowing in the motor into a D-axis current and a Q-axis current on orthogonal two-axis coordinates, generating a D-axis voltage command so that the D-axis current follows the D-axis current command, and generating a Q-axis voltage command so that the Q-axis current follows the Q-axis current command, and controlling the power converter based on the generated D-axis voltage command and the generated Q-axis voltage command,

[0170] Based on the detected value of the three-phase AC voltage, the pulsation contained in the DC voltage obtained by full-wave rectification of the three-phase AC voltage is derived as a pulsation voltage prediction value, and based on the detected value of the DC voltage, the pulsation contained in the DC voltage is derived as a pulsation voltage actual value,

[0171] At least one of the D-axis voltage command and the Q-axis voltage command is corrected by a voltage correction command generated so as to reduce a deviation between the pulsating voltage prediction value and the pulsating voltage actual measurement value.

[0172] In this way, the control unit derives the pulsation included in the DC voltage obtained by full-wave rectification of the three-phase AC voltage as the pulsation voltage prediction value based on the detection value of the three-phase AC voltage. In addition, based on the detection value of the DC voltage of the DC bus, the pulsation included in the DC voltage is derived as the pulsation voltage actual value, and the deviation between the pulsation voltage prediction value and the pulsation voltage actual value is calculated. The calculated deviation includes the pulsation component of the sixth harmonic caused by the height difference between the pulsation voltage prediction value and the pulsation voltage actual value, and also includes the pulsation of higher order exceeding the sixth order caused by the rectification action of the rectifier, the resonance of the LC resonant circuit, etc. included in the pulsation voltage actual value. The control unit generates a voltage correction command in a manner to reduce the calculated deviation, and corrects at least one of the D-axis voltage command and the Q-axis voltage command, so that the pulsation of the power supply current and the pulsation of the DC bus including high-order noise can be effectively suppressed, and the inverter can be continuously operated stably and soundly.

[0173] In particular, the voltage correction command is generated based on the deviation between the pulsating voltage prediction value and the pulsating voltage actual measurement value so as to reduce the deviation. Therefore, the pulsation can be effectively suppressed regardless of the impedance on the power supply side, and the control amount can be reduced, so the tracking performance relative to the target value is good. Therefore, high-order noise such as more than 6th order can also be effectively suppressed.

[0174] In addition, since the voltage commands of the D-axis and Q-axis are corrected instead of the current commands, pulsation can be effectively suppressed even when the current control system is not designed to have a high response. Therefore, high-order noise can be effectively reduced.

[0175] Furthermore, in the power conversion device of the present embodiment configured as described above,

[0176] The control unit derives the pulsating voltage prediction value by subtracting a minimum phase voltage from a maximum phase voltage in each phase of the three-phase AC voltage for each phase.

[0177] In this way, the predicted value of the pulsation included in the DC voltage after full-wave rectification is derived from the phase voltage of the three-phase AC voltage. As a result, the predicted value of the pulsation with a frequency six times the power supply frequency can be derived with high accuracy, excluding the pulsation caused by the rectification action of the rectifier generated in the actual circuit, the pulsation caused by the LC resonance of the LC circuit formed in the actual circuit, and the like.

[0178] Furthermore, in the power conversion device of the present embodiment configured as described above,

[0179] The control unit performs feedback control using a set control gain to reduce the deviation to derive a control amount, and generates the voltage correction command by multiplying the control amount by a first gain proportional to the voltage of the DC bus.

[0180] By performing feedback control in this manner, control responsiveness with respect to a target value can be improved, and higher-order noise can be effectively suppressed.

[0181] In addition, by using the first gain that is proportional to the voltage of the DC bus, the D-axis voltage command and the Q-axis voltage command can be corrected with an appropriate control amount, thereby suppressing excessive correction or insufficient correction. In this way, the power converter can be operated continuously in a stable and healthy manner. In addition, it is also possible to suppress pulsations with small amplitudes when the resonant frequency is inconsistent with 6 times the power supply frequency with high precision.

[0182] Furthermore, in the power conversion device of the present embodiment configured as described above,

[0183] The control unit is configured as follows:

[0184] The control amount is multiplied by the first gain configured inversely proportional to the D-axis current to generate the voltage correction command for correcting the D-axis voltage command,

[0185] The voltage correction command for correcting the Q-axis voltage command is generated by multiplying the control amount by the first gain configured inversely proportional to the Q-axis current.

[0186] By using the first gain configured in this way, the D-axis voltage command and the Q-axis voltage command can be corrected with a more appropriate control amount, the control amount of ΔIdc can be made constant, and the control effect can be kept constant. In this way, the pulsation generated in the power supply current and the DC link part can be stably eliminated, and the power converter can be continuously operated stably and soundly.

[0187] Furthermore, in the power conversion device of the present embodiment configured as described above,

[0188] At least one value of the voltage of the DC bus, the D-axis current, and the Q-axis current constituting the first gain is updated based on a detection value when the power converter is operating.

[0189] As a result, under various operating conditions such as changes in load current, it is possible to suppress insufficient control amount and variations in control effect, and to efficiently suppress pulsation.

[0190] Furthermore, in the power conversion device of the present embodiment configured as described above,

[0191] If the D-axis current or the Q-axis current reaches a value within a set first value range,

[0192] Then, the control unit performs clamp control to adjust the value of the D-axis current or the Q-axis current used in the first gain to a value exceeding the first value range.

[0193] As a result, excessive input of control variables and the like can be suppressed under various operating conditions, and the power converter can be continuously operated in a more stable and healthy manner.

[0194] Implementation Method 2

[0195] Hereinafter, Embodiment 2 of the present application will be described with reference to the drawings, focusing on the differences from Embodiment 1 described above. The same reference numerals are given to the same parts as those in Embodiment 1 described above, and the description thereof will be omitted.

[0196] The circuit configuration of the power conversion device of the second embodiment is the same as that of the first embodiment. Figure 1 The structure of the control unit 50 of this embodiment is also the same as that of the first embodiment. Figure 2The structure shown in FIG. 1 is the same as that shown in FIG. 1 , but the internal structure of the pulsation suppression control unit 30 is different.

[0197] Figure 8 1 is a control block diagram showing the internal structure of the pulsation suppression control unit 230 of the power conversion device according to the second embodiment.

[0198] The pulsation suppression control unit 230 of the second embodiment is different from the pulsation suppression control unit 30 of the first embodiment in the feedback control unit 235, the gain adjustment unit 237, and the positive and negative determination units 239d and 239q as the sign function.

[0199] In particular, unlike the first embodiment, the feedback control unit 235 for suppressing resonance is characterized in that the D-axis and the Q-axis are constructed in the same manner, and a control quantity 235C is derived that is commonly used in generating the D-axis voltage correction command ΔVd* and the Q-axis voltage correction command ΔVq* that respectively correct the D-axis voltage command Vd* and the Q-axis voltage command Vq*.

[0200] In addition, the feedback control in the feedback control unit 235 usually uses proportional (P) control. In the case of increasing the control bandwidth, it can also be composed of proportional differential (PD) control. In addition, a structure in which control using a phase lead compensation filter that makes the control amount lead the set phase amount and proportional (P) control are simultaneously performed instead of PD control can also be adopted.

[0201] Then, the gain adjustment unit 237 multiplies the control amount 235C used in common for the D-axis and the Q-axis by a gain 237G (Vdc / (|Id|+|Iq|)) which is a first gain used in common for the D-axis and the Q-axis.

[0202] The gain 237G is proportional to the DC bus voltage Vdc and inversely proportional to the sum of the absolute value of the D-axis current Id and the absolute value of the Q-axis current Iq.

[0203] Next, with respect to the D axis, the positive / negative determination unit 239d generates a voltage correction command ΔVd* by multiplying the control amount multiplied by the gain 237G by the sign function Sign(Id) that takes out only the polarity of the D axis current Id as a variable. Next, with respect to the Q axis, the positive / negative determination unit 239q generates a voltage correction command ΔVq* by multiplying the control amount multiplied by the gain 237G by the sign function Sign(Iq) that takes out only the polarity of the Q axis current Iq as a variable.

[0204] The D-axis voltage command Vd* and the Q-axis voltage command Vq* are corrected by the D-axis voltage correction command ΔVd* and the Q-axis voltage correction command ΔVq* generated in this way.

[0205] Next, the configuration of the gain 237G and the positive / negative determination units 239d and 239q according to the present embodiment will be described.

[0206] In the first embodiment, it was confirmed that ΔIdc was derived by the above-mentioned equation (19).

[0207] Here, in this embodiment, ΔVd given to the voltage command to suppress pulsation, that is, the D-axis voltage correction command ΔVd* is given by the following equation (20). In addition, ΔVq given to the voltage command intentionally to suppress pulsation, that is, the Q-axis voltage correction command ΔVq* is given by the following equation (21).

[0208]

Mathematical formula 20

[0209]

[0210]

Mathematical formula 21

[0211]

[0212] ΔVerr is a deviation between the pulsating voltage prediction value ΔVdc* and the pulsating voltage actual value ΔVdc, and corresponds to the output of the subtractor 34. In addition, the feedback control performed when deriving the above ΔVd* and ΔVq* is only proportional (P) control using a proportional gain Kp.

[0213] Here, it is a normal state that the D-axis current Id is 0 or a negative value and Iq is a positive value. Therefore, the above equations (20) and (21) can be rewritten as the following equations (22) and (23).

[0214]

Mathematical formula 22

[0215]

[0216]

Mathematical formula 23

[0217]

[0218] If equations (22) and (23) are substituted into equation (19), we obtain equation (24).

[0219]

Mathematical formula 24

[0220] ΔI dc =Id / V dc ·{-V dc / (-I d +I q )·K p ΔV err}+I q / V dc ·{V dc / (-I d +I q )·K p ΔV err}

[0221] =K p ΔV err …(twenty four)

[0222] That is, the output power of the inverter 6 represented by the above equation (19) can be made to have a simple characteristic in which the influence of the physical parameters of Vdc, Id, and Iq is offset as represented by the above equation (24).

[0223] By adjusting in this way, the control amount of ΔIdc can be made constant, and insufficient control amount, generation of pulsation, and variation in control effect due to conditions can be suppressed, thereby efficiently suppressing resonance.

[0224] Next, another gain calculation method is described. Replace the contents of the pulsation suppression control unit with Fig. 9 The pulsation suppression control unit 230A is shown.

[0225] Fig. 9 1 is a control block diagram showing the internal structure of the pulsation suppression control unit 230A of the power conversion device according to the second embodiment.

[0226] and Figure 8 The pulsation suppression control unit 230 shown is different in the gain multiplied by the control amount 235C in the gain adjustment units 237A and 238A.

[0227] On the D axis, the gain adjustment unit 237A multiplies the control amount 235C by a gain 237AG (|Id| / Id′) as a second gain in addition to multiplying the control amount 235C by a gain 237G (Vdc / (|Id|+|Iq|)) as a first gain.

[0228] In addition, on the Q axis, the gain adjustment unit 238A multiplies the control amount 235C by a gain 238AG (|Iq| / Iq′) as a second gain in addition to multiplying the control amount 235C by a gain 237G (Vdc / (|Id|+|Iq|)) as a first gain.

[0229] The gain 237AG is configured to be proportional to the absolute value of the D-axis current Id and inversely proportional to the value of the D-axis current Id that is clamped and controlled to a value exceeding the set first value range.

[0230] The gain 238AG is configured to be proportional to the absolute value of the Q-axis current Iq and inversely proportional to the value of the Q-axis current Iq that is clamped and controlled to a value exceeding the set first value range.

[0231] The denominator Id′ of the gain 237AG is the D-axis current Id after the amplitude limiting process is performed by the clamp control, and the denominator Iq′ of the gain 238AG is the Q-axis current Iq after the amplitude limiting process is performed by the clamp control.

[0232] The output is clamped by the limiting process performed by the clamp control so that the absolute values ​​of the D-axis current Id and the Q-axis current Iq do not fall within the set first value range. For example, when the first value range is set to -9A to 9A, the current is clamped to 9.1A when 7A is input. Conversely, the current is clamped to -9.1A when -7A is input.

[0233] Thus, even when the absolute values ​​of the D-axis current Id and the Q-axis current Iq are small, the voltage command is not corrected excessively.

[0234] If this control block is used, for example, when Id = 0A, the voltage correction command ΔVd* = 0V by executing clamp control. On the contrary, when neither the D axis nor the Q axis is clamped, the voltage correction command ΔVd* = 0V. Figure 8 The pulsation suppression control of the structure shown has the same action.

[0235] In the power conversion device of this embodiment configured as described above,

[0236] The control unit generates the voltage correction command for correcting the D-axis voltage command and the Q-axis voltage command by multiplying the control amount by the first gain inversely proportional to the sum of the absolute value of the D-axis current and the absolute value of the Q-axis current.

[0237] Furthermore, in the power conversion device of the present embodiment configured as described above,

[0238] In the feedback control, the control unit derives the control amount commonly used in generating the voltage correction command for correcting the D-axis voltage command and the Q-axis voltage command.

[0239] By using the first gain of such a structure, the D-axis voltage command and the Q-axis voltage command can be corrected with an appropriate control amount, and both the D-axis and the Q-axis can realize feedback control through one structure. In this way, the feedback control performed in the control unit can be reduced, and the same first gain can be used for the D-axis and the Q-axis to derive a control amount that can be used in common in the generation of the voltage correction command for correcting the D-axis and the Q-axis voltage commands, thereby simplifying the control structure and reducing the control load of the control unit. In this way, a high-speed response of the feedback control can be realized, and high-order pulsation can be effectively suppressed.

[0240] Furthermore, in the power conversion device of the present embodiment configured as described above,

[0241] In a structure in which the first gain is inversely proportional to the sum of the absolute value of the D-axis current and the absolute value of the Q-axis current,

[0242] The control unit multiplies the control amount used in common in correcting the D-axis voltage instruction and the Q-axis voltage instruction by a sign function that only takes out the polarity of the D-axis current as a variable to generate the voltage correction instruction for correcting the D-axis voltage instruction, and multiplies the control amount by a sign function that only takes out the polarity of the Q-axis current as a variable to generate the voltage correction instruction for correcting the Q-axis voltage instruction.

[0243] In this way, by adopting a structure in which the voltage correction command is generated by multiplying the control amount by a sign function that only extracts the polarity of the D-axis and Q-axis currents with respect to the same control amount used in common for the D-axis and Q-axis, the output of the power converter can be controlled by a simple characteristic of multiplying the deviation ΔVerr by the gain Kp. In this way, the power converter can be continuously operated stably and soundly under various operating conditions.

[0244] Furthermore, in the power conversion device of the present embodiment configured as described above,

[0245] In a structure in which the first gain is inversely proportional to the sum of the absolute value of the D-axis current and the absolute value of the Q-axis current,

[0246] The control unit multiplies the control amount commonly used in correcting the D-axis voltage command and the Q-axis voltage command by a second gain in addition to the first gain.

[0247] The second gain is constituted as follows:

[0248] is proportional to the absolute value of the D-axis current and inversely proportional to the value of the D-axis current that is clamped and controlled to a value exceeding a set first value range,

[0249] or,

[0250] The Q-axis current is proportional to the absolute value of the Q-axis current and is inversely proportional to the value of the Q-axis current that is clamped and controlled to a value exceeding a set first value range.

[0251] Thus, even when the driving conditions of the electric motor change, it is possible to suppress excessive correction, and the inverter can be continuously operated stably and soundly while suppressing pulsation.

[0252] This application describes various exemplary embodiments and examples, but various features, methods, and functions described in one or more embodiments are not limited to application in specific embodiments and can be applied to the embodiments alone or in various combinations.

[0253] Therefore, numerous modifications not shown in the examples are conceivable within the scope of the technology disclosed in this application, including, for example, the modification, addition or omission of at least one constituent element, and the extraction of at least one constituent element and the combination with constituent elements of other embodiments.

[0254] Description of Reference Numerals

[0255] 2 rectifier (rectification unit), 6 inverter (power converter), 7 motor (electric motor), 50 control unit, 37G, 38G gain (first gain), 100 power conversion device, P, N DC bus.

Claims

1. A power conversion device, wherein: The power conversion device comprises: A rectifier unit, which converts the input three-phase AC voltage into a DC voltage and outputs it to a DC bus; a power converter, the power converter converting the DC voltage in the DC bus converted by the rectifying unit into an AC voltage to control the motor; as well as a control unit that controls the power converter, The control unit is configured as follows: converting the current flowing in the motor into a D-axis current and a Q-axis current on orthogonal two-axis coordinates, generating a D-axis voltage command so that the D-axis current follows the D-axis current command, and generating a Q-axis voltage command so that the Q-axis current follows the Q-axis current command, and controlling the power converter based on the generated D-axis voltage command and the generated Q-axis voltage command, Based on the detected value of the three-phase AC voltage, the pulsation contained in the DC voltage obtained by full-wave rectification of the three-phase AC voltage is derived as a pulsation voltage prediction value, and based on the detected value of the DC voltage, the pulsation contained in the DC voltage is derived as a pulsation voltage actual value, At least one of the D-axis voltage command and the Q-axis voltage command is corrected by a voltage correction command generated so as to reduce a deviation between the pulsating voltage prediction value and the pulsating voltage actual measurement value.

2. The power conversion device according to claim 1, wherein: The control unit derives the pulsating voltage prediction value by subtracting a minimum phase voltage from a maximum phase voltage in each phase of the three-phase AC voltage for each phase.

3. The power conversion device according to claim 1 or 2, wherein: The control unit performs feedback control using a set control gain to reduce the deviation to derive a control amount, and generates the voltage correction command by multiplying the control amount by a first gain proportional to the voltage of the DC bus.

4. The power conversion device according to claim 3, wherein: The control unit is configured as follows: The control amount is multiplied by the first gain configured inversely proportional to the D-axis current to generate the voltage correction command for correcting the D-axis voltage command, The voltage correction command for correcting the Q-axis voltage command is generated by multiplying the control amount by the first gain configured inversely proportional to the Q-axis current.

5. The power conversion device according to claim 3, wherein: The control unit generates the voltage correction command for correcting the D-axis voltage command and the Q-axis voltage command by multiplying the control amount by the first gain inversely proportional to the sum of the absolute value of the D-axis current and the absolute value of the Q-axis current.

6. The power conversion device according to claim 5, wherein: In the feedback control, the control unit derives the control amount commonly used in generating the voltage correction command for correcting the D-axis voltage command and the Q-axis voltage command.

7. The power conversion device according to claim 6, wherein: In a structure in which the first gain is inversely proportional to the sum of the absolute value of the D-axis current and the absolute value of the Q-axis current, The control unit multiplies the control amount used in common in correcting the D-axis voltage instruction and the Q-axis voltage instruction by a sign function that only takes out the polarity of the D-axis current as a variable to generate the voltage correction instruction for correcting the D-axis voltage instruction, and multiplies the control amount by a sign function that only takes out the polarity of the Q-axis current as a variable to generate the voltage correction instruction for correcting the Q-axis voltage instruction.

8. The power conversion device according to claim 5 or 6, wherein: In a structure in which the first gain is inversely proportional to the sum of the absolute value of the D-axis current and the absolute value of the Q-axis current, The control unit multiplies the control amount commonly used in correcting the D-axis voltage command and the Q-axis voltage command by a second gain in addition to the first gain. The second gain is constituted as follows: is proportional to the absolute value of the D-axis current and inversely proportional to the value of the D-axis current that is clamped and controlled to a value exceeding a set first value range, or, The Q-axis current is proportional to the absolute value of the Q-axis current and is inversely proportional to the value of the Q-axis current that is clamped and controlled to a value exceeding a set first value range.

9. The power conversion device according to any one of claims 3 to 8, wherein: The feedback control performs any one of proportional control, proportional differential control, and control in which the control amount is advanced by a set phase amount and proportional control are performed simultaneously.

10. The power conversion device according to claim 4, wherein: If the D-axis current or the Q-axis current reaches a value within a set first value range, Then, the control unit performs clamp control to adjust the value of the D-axis current or the Q-axis current used in the first gain to a value exceeding the first value range.

11. The power conversion device according to any one of claims 3 to 10, wherein: At least one value of the voltage of the DC bus, the D-axis current, and the Q-axis current constituting the first gain is updated based on a detection value when the power converter is operating.

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