JP2014036479A - Control device of electric power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power conversion device which reduces a high frequency component of a DC voltage of an inverter without depending upon response of current control.SOLUTION: A high frequency component acquisition part 45 acquires a high frequency component of a DC voltage which is larger than 2N times as high as the frequency of an N-phase AC voltage. A command generation part 48 generates a d-axis voltage command Vd** for a d-axis voltage component of an AC voltage applied to a rotary machine and a q-axis voltage command Vq* for a q-axis voltage component on dq-axis rotary coordinates which rotate as the rotary machine rotates and have a "d" axis in phase with the pole center of a field of the rotary machine and a "q" axis orthogonal in phase to the "d" axis. A correction part 46 corrects only the d-axis voltage command Vd** into a higher voltage as the high frequency component is higher so as to generate a d-axis voltage command Vd* after correction. A control signal generation part 47 outputs a control signal to an electric power conversion part on the basis of the d-axis voltage command Vd* after correction and the q-axis voltage command Vq*.

Description

  The present invention relates to a control device for a power conversion device, for example, a control device for a capacitorless inverter.

  Patent Document 1 describes an electric motor control device. The electric motor control device has a converter and an inverter. The converter receives an AC voltage, converts it into a DC voltage, and outputs it to the DC link. The inverter receives the DC voltage, converts it to an AC voltage, and outputs it to the motor. The DC link is provided with a capacitor. As this capacitor, a capacitor having a small capacitance is employed. Therefore, the capacitor does not sufficiently smooth the DC voltage output from the converter, and the DC voltage pulsates.

  Therefore, in Patent Document 1, the voltage of the capacitor is detected, and the voltage command for the AC voltage output from the inverter is corrected so that the pulsation is not transmitted to the output of the inverter. For example, the output of the inverter is made substantially constant by performing a correction that reduces the voltage command as the voltage of the capacitor increases.

  In Patent Document 1, a reactor is provided on the input side of the converter. This capacitor and the reactor form an LC filter. Therefore, the capacitor voltage can vibrate due to the resonance of the LC filter.

  Therefore, in Patent Document 1, the vibration component is extracted from the voltage of the capacitor, and the current command for the alternating current output from the inverter or the torque command or the rotation command for the electric motor is corrected so as to reduce this vibration component. . This also reduces vibration components due to the LC filter.

  Techniques related to the present invention are described in Patent Documents 2 and 3 and Non-Patent Document 1.

JP 2007-181358 A Patent No. 4067021 JP 2009-17673 A

Sugimoto and two others, “Theory and design of AC server systems: from basics to software servos”, Sogaku Publishing Co., pp. 117

  However, in Patent Document 1, in order to suppress the oscillation of the voltage of the capacitor due to the resonance of the LC filter, the current command is corrected instead of the output voltage command.

  The upper limit of the current control response depends on the carrier frequency for switching the switching element of the inverter. Non-Patent Document 1 describes that the limit of the current control response is about 6000 rad / sec (955 Hz) when the carrier frequency is 3 kHz. That is, if the carrier frequency of the inverter is low, the current control response is lowered, so that the current control does not sufficiently function and the desired stabilization cannot be performed.

  That is, when the carrier frequency is 3 kHz or less, an unstable phenomenon due to a resonance frequency (resonance frequency of the LC filter) of 955 Hz or more cannot be suppressed due to a limit due to a current control response. That is, depending on the combination of the capacitor and the inductance and the carrier frequency, the pulsation component of the correction value corresponding to the voltage component detected from the DC voltage becomes higher than the responsiveness of the current control, and the correction value passes the current control (for example, PI control). As a result, components (or amounts) necessary for stability are attenuated, and desired stability and control performance cannot be obtained.

  This invention is made | formed in view of the said situation, The objective is to provide the control apparatus of the power converter device which reduces the high frequency component of DC voltage, without depending on the response of current control.

  A first aspect of a control device for a power conversion device according to the present invention is a full-wave rectification of an N (N is a natural number) phase AC voltage input via an input line to convert the DC voltage into first and second DC voltages. Based on the rectification unit (1) that is output between the DC lines (LH, LL) and the input control signal, the DC voltage is converted into an AC voltage, and the AC voltage is output to the rotating machine (M1). A high-frequency component acquisition unit (45) for acquiring a high-frequency component higher than 2N times the frequency of the N-phase AC voltage; , In the dq axis rotation coordinate having a d axis in phase with the pole center of the field of the rotating machine and a q axis whose phase is orthogonal to the d axis. D-axis voltage command (Vd **) for the d-axis voltage component and q-axis voltage command (Vq *) for the q-axis voltage component. ) And a correction unit (46) that generates a corrected d-axis voltage command (Vd *) by performing correction to increase only the d-axis voltage command as the high-frequency component is higher. And a control signal generator (47) that outputs the control signal to the power converter based on the corrected d-axis voltage command and the q-axis voltage command.

  A second aspect of the control device for the power conversion device according to the present invention is the control device for the power conversion device according to the first aspect, wherein the capacitor is provided between the first and second DC lines. And a voltage detector (5) for detecting a DC voltage of the capacitor, and the high-frequency component acquisition unit (45) extracts the high-frequency component from the DC voltage of the capacitor.

  A third aspect of the control device for the power conversion device according to the present invention is a control device for the power conversion device according to the first aspect, in which a capacitor (between the first and second DC lines) is provided. C1), a reactor (L1) provided on the first or second DC line (LH, LL), and a voltage (VL1) applied to the reactor, on the rectifying unit (1) side of the capacitor. ), And the high-frequency component acquisition unit (45) extracts the high-frequency component from the voltage.

  A fourth aspect of the control device for the power conversion device according to the present invention is the control device for the power conversion device according to the first aspect, and is applied to the reactor (L2) provided in the input line and the reactor. And a reactor voltage detector (6) for detecting the voltage (VL2), and the high-frequency component acquisition unit (45) extracts the high-frequency component from the voltage.

  According to the first, third, and fourth aspects of the control device for the power converter according to the present invention, the corrected d-axis voltage command increases as the high-frequency component of the DC voltage increases. The amplitude of the AC voltage output from the power source increases, and as a result, the power output from the power converter increases. Since the DC voltage on the input side decreases as the power on the output side increases, the DC voltage can be reduced when the high frequency component of the DC voltage is high. Therefore, this high frequency component can be reduced.

  Moreover, since the voltage command is corrected, the DC voltage can be stabilized without depending on the response of the current control. Therefore, it is possible to stabilize the DC voltage using a low-cost microcomputer with poor arithmetic processing capability even if the current control response is low at a low carrier frequency.

  Further, the present control device can be applied even if the rotating machine has no saliency. This is because when the rotating machine has no saliency, the power output from the power converter does not depend on the q-axis voltage but depends on the d-axis voltage.

  According to the 2nd aspect of the control apparatus of the power converter device concerning this invention, since a high frequency component is extracted from DC voltage, extraction is easy.

It is a figure which shows an example of a notional structure of a power converter device. It is a figure which shows an example of a notional structure of a control part. It is a figure which shows an example of a notional structure of a power converter device. It is a figure which shows typically an example of a direct-current voltage and the alternating current of an input side. It is a figure which shows typically an example of a direct-current voltage and the alternating current of an input side. It is a figure which shows typically an example of a direct-current voltage and the alternating current of an input side. It is a figure which shows an example of a notional structure of a power converter device. It is a figure which shows an example of a notional structure of a power converter device. It is a figure which shows an example of a notional structure of a power converter device. It is a figure which shows an example of a direct-current voltage, an input side alternating current, and an output side alternating current. It is a figure which shows an example of a direct-current voltage, an input side alternating current, and an output side alternating current. It is a figure which shows an example of a notional structure of a power converter device.

First embodiment.
As shown in FIG. 1, the power conversion device includes a rectification unit 1 and a power conversion unit 3. The rectifying unit 1 performs full-wave rectification on the N-phase AC voltage input via the input line, and outputs a DC voltage between the DC lines LH and LL. In the illustration of FIG. 1, the rectifier 1 is a diode rectifier circuit. However, the rectifier 1 is not limited to the diode rectifier circuit, and may be a separately excited rectifier circuit or a self-excited rectifier circuit. As the separately excited rectifier circuit, for example, a thyristor bridge rectifier circuit can be adopted, and as the self-excited rectifier circuit, for example, a PWM (Pulse-Width-Modulation) type AC-DC converter can be adopted.

  In the illustration of FIG. 1, the rectifying unit 1 is a single-phase rectifier circuit to which a single-phase AC voltage is input. However, the number of phases of the AC voltage input to the rectifying unit 1, that is, the number of phases of the rectifying unit 1 is not limited to a single phase, and may be set as appropriate.

  In the illustration of FIG. 1, a capacitor C1 is provided between the DC lines LH and LL. The capacitor C1 is a film capacitor, for example. Such a capacitor C1 is less expensive than an electrolytic capacitor. On the other hand, the capacitance of the capacitor C1 is smaller than the capacitance of the electrolytic capacitor, and the DC voltage between the DC lines LH and LL is not sufficiently smoothed. In other words, the capacitor C1 allows pulsation of the DC voltage of the DC lines LH and LL. Therefore, the DC voltage has a pulsation component (that is, a pulsation component having a frequency 2N times the frequency of the N-phase AC voltage) due to full-wave rectification of the N-phase AC voltage.

  In the illustration of FIG. 1, a reactor L2 is provided. Reactor L2 is provided on an input line connected to rectifying unit 1. However, the present invention is not limited to this. For example, as shown in FIG. 3, a reactor L1 may be provided. Reactor L1 is provided on DC line LH or DC line LL (DC line LH in FIG. 3) on the rectifying unit 1 side with respect to capacitor C1.

  Since the reactor L2 (or L1) and the capacitor C1 are connected in series between the pair of output terminals of the AC power supply E1, a so-called LC filter is formed. Since the capacitance of the capacitor C1 is small as described above, the resonance frequency of the LC filter tends to increase. Similarly, as the inductance of reactor L2 (or L1) is decreased, the resonance frequency tends to be further increased. For example, in FIG. 3, when the capacitance of the capacitor C1 is 40 μF and the inductance of the reactor L1 is 0.7 mH, the resonance frequency is about 951 Hz.

  The power conversion unit 3 is an inverter, for example, and inputs a DC voltage between the DC lines LH and LL. The power conversion unit 3 converts the DC voltage into an AC voltage based on a control signal from the control unit 4, and outputs the AC voltage to the rotating machine M1. In the illustration of FIGS. 1 and 3, the power conversion unit 3 includes, for example, a pair of switching units connected in series between the DC lines LH and LL for three phases. In the example of FIG. 1, a pair of switching units Sup and Sun are connected in series, a pair of switching units Svp and Svn are connected in series, and a pair of switching units Swp and Swn are connected in series. A connection point between a pair of switching units Sxp, Sxn (x represents u, v, w, and so on) of each phase is connected to the rotating machine M1 via the output line Px. When these switching units Sxp and Sxn are turned on / off based on an appropriate control signal, the power conversion unit 3 converts the DC voltage into a three-phase AC voltage and outputs it to the rotating machine M1.

  The rotating machine M1 is an AC rotating machine and may be an induction machine or a synchronous machine. 1 and 3 exemplify a three-phase rotating machine M1, the number of phases is not limited thereto. In other words, the power converter 3 is not limited to a three-phase power converter.

<Control unit 4>
The control unit 4 generates a control signal to be given to the power conversion unit 3 (more specifically, the switching units Sxp and Sxn), and controls the power conversion unit 3. Referring to FIG. 2, the control unit 4 includes a voltage command generation unit 48, a high frequency component acquisition unit 45, a correction unit 46, and a control signal generation unit (hereinafter referred to as a PWM control unit) 47.

  Here, the control unit 4 includes a microcomputer and a storage device. The microcomputer executes each processing step (in other words, a procedure) described in the program. The storage device is composed of one or more of various storage devices such as a ROM (Read Only Memory), a RAM (Random Access Memory), a rewritable nonvolatile memory (EPROM (Erasable Programmable ROM), etc.), and a hard disk device, for example. Is possible. The storage device stores various information, data, and the like, stores a program executed by the microcomputer, and provides a work area for executing the program. It can be understood that the microcomputer functions as various means (for example, the voltage command generation unit 48, the high frequency component acquisition unit 45, the correction unit 46, and the PWM control unit 47) corresponding to each processing step described in the program, Alternatively, it can be understood that various functions corresponding to each processing step are realized. The controller 4 is not limited to this, and various procedures executed by the controller 4 or various means or various functions implemented may be realized by hardware.

  The voltage command generator 48 generates a d-axis voltage command Vd ** and a q-axis voltage command Vq * in the dq-axis rotation coordinates. The dq-axis rotation coordinates are coordinates that rotate according to the rotation of the rotating machine M1, and are formed by the d-axis and the q-axis that are orthogonal to each other. The d axis is an axis in phase with the magnetic field center of the field of the rotating machine M1, and the q axis is an axis whose phase is orthogonal to the d axis. The d-axis voltage command Vd ** is a command for the d-axis voltage component (so-called d-axis voltage) of the AC voltage output by the power converter 3, and the q-axis voltage command Vq * is the q-axis voltage of the AC voltage. This is a command for a voltage component (so-called q-axis voltage).

  The voltage command generator 48 may generate the d-axis voltage command Vd ** and the q-axis voltage command Vq * using any known method. An example will be described in detail below. For example, the voltage command generator 48 includes a speed controller 41, a current controller 42, a dq axis / three-phase converter 43, and a phase calculator 44.

  The speed control unit 41 inputs a rotational speed command ω * for the rotational speed ω of the rotating machine M1 from the outside (not shown). The speed controller 41 also inputs the rotational speed ω (detected value) of the rotating machine M1. The rotational speed ω is detected by the rotational speed detector 8 shown in FIGS. The rotational speed detector 8 detects the rotational speed ω of the rotating machine M1 by any known method. For example, the rotation speed detection unit 8 may be a rotation speed sensor provided in the rotating machine M1. Alternatively, the rotational speed detector 8 may estimate the rotational speed ω from the alternating current flowing through the rotating machine M1.

  The speed control unit 41 generates a current command Ia * so that the rotational speed command ω * and the rotational speed ω coincide with each other. This current command Ia * is a command for the amplitude of the alternating current flowing through the rotating machine M1. For example, the speed controller 41 employs PI (proportional integral) control or PID (proportional integral derivative) control to generate the current command Ia *.

  The current control unit 42 inputs a current command Ia * from the speed control unit 41 and a phase command β * from the outside (not shown), for example. The phase command β * is the phase with respect to the q axis of the current obtained by converting the alternating current flowing through the rotating machine M1 into the dq axis rotating coordinate system.

  The current control unit 42 also receives the d-axis current id, which is the d-axis component in the dq-axis rotation coordinates of the alternating current flowing through the rotating machine M1, and the q-axis current iq, which is the q-axis component. These d-axis current id and q-axis current iq are acquired as follows, for example.

  In the illustrations of FIGS. 1 and 3, the alternating current flowing through the rotating machine M <b> 1 is detected by the current detection unit 7. As the current detector 7, for example, a current transformer can be adopted. 1 and 3 exemplify a three-phase rotating machine M1, the current detector 7 detects a two-phase alternating current. Since the sum of the three-phase alternating currents is ideally zero, if the two-phase alternating current is detected, the remaining one-phase alternating current can be calculated. The current detector 7 may detect a three-phase alternating current. Further, although the current detection unit 7 is provided on the output side of the power conversion unit 3, it may be provided on the input side, that is, the DC line LH or the DC line LL. In this case, the current detection unit 7 detects the direct current flowing through the direct current line LH or the direct current line LL as an alternating current of a phase determined by the switching pattern of the power conversion unit 3. Since this detection method is a known technique, a detailed description thereof is omitted.

  Here, the alternating currents iu and iv flowing through the output lines Pu and Pv are detected and input to the dq axis / three-phase converter 43 (see FIG. 2). The phase θ is also input from the phase calculator 44 to the dq axis / three-phase converter 43. This phase θ is a phase difference between the three-phase fixed coordinates and the dq axis rotation coordinates. The phase calculator 44 integrates the rotational speed ω acquired from the rotational speed detector 8 to calculate the phase θ, and outputs this to the dq axis / three-phase converter 43. The dq axis / three-phase conversion unit 43 performs known coordinate conversion on the alternating currents iu and iv based on the phase θ, and calculates the d-axis current id and the q-axis current iq in the dq-axis rotation coordinates. Then, the d-axis current id and the q-axis current iq are input to the current control unit 42.

  Based on the current command Ia * and the phase command β * and the d-axis current id and the q-axis current iq, the current control unit 42 outputs the d-axis voltage command Vd ** and the q-axis voltage command Vq * by a known method. Generate. For example, the d-axis current command and the q-axis current command are calculated based on the current command Ia * and the phase command β *, the deviation between the d-axis current command and the d-axis current id, and the q-axis current command and the q-axis current iq. The d-axis voltage command Vd ** and the q-axis voltage command Vq * are generated so that both of the deviations from the above approach zero. For example, the deviation between the d-axis current command and the d-axis current id is amplified to generate the d-axis voltage command Vd **, and the deviation between the q-axis current command and the q-axis current iq is amplified to obtain the q-axis voltage. This can be realized by generating the command Vq *.

  The d-axis voltage command Vd ** is output to the correction unit 46, and the q-axis voltage command Vq * is output to the PWM control unit 47.

  The high frequency component acquisition unit 45 acquires a high frequency component of a DC voltage between the DC lines LH and LL. The high-frequency component here is a high-frequency component higher than 2N times the frequency of the N-phase AC voltage input to the rectifying unit 1. That is, the high frequency component acquisition unit 45 acquires a high frequency component having a higher frequency than the pulsation component due to full-wave rectification of the N-phase AC voltage. Such high frequency components include resonance frequency components due to the capacitor C1 and the reactor L2.

  In the example of FIGS. 1 and 3, a DC voltage detection unit 5 that detects the DC voltage Vdc of the capacitor C <b> 1 is provided. The DC voltage Vdc detected by the DC voltage detection unit 5 is input to the high frequency component acquisition unit 45.

  The high frequency component acquisition unit 45 extracts a high frequency component of the DC voltage Vdc. The high frequency component acquisition unit 45 includes, for example, an LPF unit 451, a subtraction unit 452, and a gain unit 453. The LPF unit 451 receives the DC voltage Vdc, removes a high frequency component higher than 2N times the frequency of the N-phase AC voltage, and outputs a low frequency component.

  1 and 3, a single-phase AC voltage is input to the rectifying unit 1. For example, when the frequency of the single-phase AC voltage is 50 Hz, the frequency of the DC voltage pulsation by full-wave rectification is 100 (= 2 × number of phases × 50) Hz. Further, assuming that the resonance frequency by the capacitor C1 and the reactor L2 is about 951 Hz, the cutoff frequency of the LPF unit 451 can be set as follows, for example. That is, the cutoff frequency of the LPF unit 451 can be set to about 430 Hz, for example, so that the 100 Hz frequency component of the DC voltage Vdc can be sufficiently passed and the frequency component of the resonance frequency 951 Hz can be sufficiently removed.

  The low frequency component output from the LPF unit 451 is input to the subtraction unit 452. The subtractor 452 also receives the DC voltage Vdc, subtracts the low frequency component from the DC voltage Vdc, and outputs the result. Therefore, the subtraction unit 452 outputs a high frequency component of the DC voltage Vdc.

  The gain unit 453 receives the high frequency component of the DC voltage Vdc from the subtraction unit 452. The gain unit 453 multiplies this high frequency component by a gain, and outputs this to the correction unit 46 as a correction value.

  The correction unit 46 performs correction to increase the d-axis voltage command Vd ** as the high frequency component of the DC voltage Vdc is higher. The correction unit 46 is, for example, an addition unit, and adds a correction value to the d-axis voltage command Vd ** and outputs it as a d-axis voltage command Vd *.

  The PWM control unit 47 receives the d-axis voltage command Vd * from the correction unit 46 and the q-axis voltage command Vq * from the voltage command generation unit 48, generates a control signal based on these, and generates the power conversion unit 3 To output. Such generation of the control signal is performed using any known technique. For example, a known coordinate transformation is performed on the d-axis voltage command Vd * and the q-axis voltage command Vq * to generate a three-phase voltage command. Then, by comparing the three-phase voltage command with a predetermined carrier, the comparison result can be generated as a control signal.

  According to such a control method, since the d-axis voltage command Vd * increases as the high frequency component of the DC voltage Vdc increases, the amplitude of the AC voltage output from the power conversion unit 3 when the high frequency component is high is increased. Can do. As a result, the electric power which the power converter 3 outputs increases. Since the DC voltage Vdc on the input side decreases as the power on the output side of the power converter 3 increases, the DC voltage Vdc can be reduced when the high frequency component of the DC voltage Vdc is high. Therefore, this high frequency component can be reduced.

  In addition, according to the present control method, the voltage command is corrected, so that the high frequency component of the DC voltage can be reduced without depending on the response of the current control. In other words, it is possible to use an inexpensive microcomputer with poor arithmetic processing capability. In addition, unlike the present control method, in the control method for correcting the current command, the current control response cannot be increased due to the carrier frequency restriction, and the high frequency component of the DC voltage cannot be sufficiently suppressed. However, since this control method can also avoid such a problem, the high frequency component of the DC voltage can be reduced without increasing the carrier frequency.

  1 and 3, the power source impedance (including the resistance component and the inductance component) is simply shown as the reactor 9 in the input line of the rectifying unit 1. This power supply impedance forms an LC filter together with the reactor L2 (or L1) and the capacitor C1. Since the power supply impedance also depends on the length of the power supply wiring and the like, various values can be taken according to the site where the power converter is employed. Therefore, the resonance frequency of the LC filter including the power supply impedance can take various values depending on the site.

  Unlike the control method, when the high-frequency component of the DC voltage Vdc is not suppressed, the DC voltage may fluctuate (for example, resonate) depending on the value taken by the wiring inductance.

  On the other hand, according to this control method, even if various power supply impedances are provided on the input side of the rectifying unit 1, fluctuation (for example, resonance) of the DC voltage Vdc corresponding to the power supply impedance is suppressed. This is because the power converter 3 is controlled so that the high frequency component of the DC voltage Vdc is reduced. Therefore, such fluctuations can be suppressed. In other words, resonance of the LC filter composed of the reactor L2 (or L1) and the capacitor C1 can be suppressed. In addition, the selectivity of the power supply wiring can be improved thereby, and various power supply wirings can be employed.

  4 shows the DC voltage Vdc of the capacitor C1 and the AC current Is flowing through the input line of the rectifying unit 1 in the power conversion device of FIG. In FIG. 4, a 6 kW synchronous machine is adopted as the rotating machine M1, and the wiring inductance and the wiring resistance are set to 0.4572 mH and 0.05125Ω, respectively, as the power supply impedance. In FIG. 4, the waveform of the DC voltage Vdc is indicated by a solid line, and the waveform of the AC current Is is indicated by a broken line.

  For comparison, FIG. 5 shows the DC voltage Vdc and the AC current Is when the voltage command is not corrected. In FIG. 5, the same conditions as those in FIG. 4 are adopted except for the presence or absence of correction.

  From the comparison between FIG. 4 and FIG. 5, when this control method is implemented, it is confirmed that the high frequency component (including the resonance frequency component) of the waveform of the DC voltage Vdc is reduced, and the effect of realizing a stable DC voltage Vdc is confirmed. it can. Further, by reducing the high frequency component of the DC voltage Vdc, the harmonic component of the AC current Is is also reduced.

  This control method is repeatedly executed at a control cycle sufficiently shorter than the cycle of the AC voltage of the AC power supply E1. Therefore, the power output from the power conversion unit 3 that varies according to the present control method is the power in the control cycle. That is, by correcting the voltage command in a fine control cycle, the power in the control cycle is changed to suppress fine fluctuations (harmonic components) of the DC voltage Vdc in FIG.

  On the other hand, in paragraph 0018 of Patent Document 3, when the capacitance of the capacitor provided in the DC link (DC lines LH and LL in the present embodiment) is reduced, the control system is caused by resonance of the LC filter including the power source impedance. Describes the conditions under which is unstable. The power source impedance here is an impedance between the rectifying unit 1 and the AC power source E1, and is simply indicated by the reactor 9 in FIGS.

  Patent Document 3 describes, as one of the conditions, “(e) The greater the motor output, the more likely to become unstable”. The motor output is considered to be equivalent to the power output from the power conversion unit 3 of the present embodiment. However, the power here is, for example, power in about one cycle of the AC voltage, and the period is different from the power to be changed by the present control method.

  According to the present control method, the harmonic component of the DC voltage Vdc can be reduced by appropriately varying the power in the short control cycle, so that even if the power in one cycle of the AC voltage is large, for example, Instability can be suppressed.

  Moreover, according to this control method, only the d-axis voltage command Vd ** is corrected without performing the above-described correction for the q-axis voltage command Vq *. In describing the significance of this point, first, the power P on the output side of the power converter 3 is formulated. Here, when the rotating machine M1 is a synchronous machine, the state equation of the voltage and current of the synchronous machine expressed only by the steady term ignoring the transient term can be described as the equation (1).

Vd = R · id−ω · Lq · iq
Vq = R · iq + ω · Ld · id + ω · φa (1)

  Here, R represents the resistance component of the armature of the rotating machine M1, Ld and Lq represent the d-axis inductance and q-axis inductance of the rotating machine M1, respectively, and φa represents the magnetic flux for the field of the rotating machine M1. .

  Since the high frequency component of the DC voltage Vdc increases in the region where the rotational speed ω is high, the equation (1) can be approximated as the equation (2).

  By transforming equation (2) to express q-axis current iq by d-axis voltage Vd and d-axis current id by q-axis voltage Vq, equation (3) is derived.

  On the other hand, the electric power P output from the power conversion unit 3 can be expressed by Expression (4) using the d-axis voltage Vd, the d-axis current id, the q-axis voltage Vq, and the q-axis current iq.

  P = Vd · id + Vq · iq (4)

  When Expression (3) is substituted into Expression (4), the electric power P output from the power conversion unit 3 can be expressed by the q-axis voltage Vq and the d-axis voltage Vd as shown in Expression (5).

  As can be understood from the equation (5), even when Lq = Ld, that is, when the rotating machine M1 does not have saliency, the power conversion unit is changed by changing the d-axis voltage Vd. The electric power P output by 3 can be changed. On the other hand, when Lq = Ld, the coefficient of the q-axis voltage Vq is zero, and at this time, the power P does not depend on the q-axis voltage Vq. Therefore, even if the q-axis voltage Vq is changed for the rotating machine M1 having no saliency, the power P output from the power conversion unit 3 cannot be changed.

  As described above, according to this control method, the d-axis voltage command is corrected, so that the electric power P can be adjusted even for the rotating machine M1 having no saliency, and accordingly, the high-frequency component of the DC voltage Vdc can be appropriately adjusted. Can be reduced.

  Next, the high-frequency component of the DC voltage Vdc when the rotating machine M1 having saliency is employed and the q-axis voltage command Vq * is corrected only unlike the present control method will be considered. FIG. 6 shows the DC voltage Vdc and the AC current Is when only the q-axis voltage command Vq * is corrected. The conditions in FIG. 6 are the same as the conditions in FIG. 4 except that the correction target is different.

  From a comparison between FIG. 4 and FIG. 6, the high frequency component of the DC voltage Vdc when only the q-axis voltage command Vq * is corrected is compared with the DC voltage Vdc when only the d-axis voltage command Vd ** is corrected. Slightly more. That is, by correcting only the d-axis voltage command Vd **, it is possible to further suppress the high-frequency component of the DC voltage Vdc as compared to the case of correcting only the q-axis voltage command Vq *.

  It is also desirable to correct the d-axis voltage command Vd ** from the following points. That is, if the rotation speed ω is constant and the voltage command is not corrected, the d-axis voltage Vd and the q-axis voltage Vq can be regarded as substantially constant. The constant rotation speed ω can be realized in the steady state of the rotating machine M1. Referring to Expression (5), when correcting the d-axis voltage Vd in a steady state, the power P output from the power converter 3 is substantially proportional to the d-axis voltage Vd. Therefore, it is easier to control the power P when correcting the d-axis voltage Vd than when correcting the q-axis voltage Vq.

Second embodiment.
In the first embodiment, the DC voltage Vdc of the capacitor C1 is detected. In the second embodiment, voltage VL2 of reactor L2 is detected with reference to FIG. The power conversion device in FIG. 7 has the same configuration as the power conversion device in FIG. 1, but a reactor voltage detection unit (hereinafter simply referred to as a voltage detection unit) 6 is provided instead of the DC voltage detection unit 5. The voltage detector 6 detects the voltage VL2 of the reactor L2 and outputs it to the controller 4.

  Further, although the configuration of the control unit 4 according to the second embodiment has the same configuration as the configuration of FIG. 2, the high frequency component acquisition unit 45 receives the voltage VL2 of the reactor L2 instead of the DC voltage Vdc of the capacitor C1. Is done. Here, voltage VL2 of reactor L2 is a voltage based on the potential on the AC power supply E1 side.

  Since the high frequency component of the DC voltage Vdc of the capacitor C1 is also transmitted to the input side of the rectifier 1, the high frequency component of the DC voltage Vdc of the capacitor C1 appears in the voltage VL2 of the reactor L2.

  Therefore, in the second embodiment, the voltage VL2 of the reactor L2 is input to the high frequency component acquisition unit 45. The high-frequency component acquisition unit 45 extracts a high-frequency component (a frequency component larger than a frequency 2N times the frequency of the N-phase AC voltage) from the voltage VL2 of the reactor L2, and multiplies this by a gain to the correction unit 46 as a correction value. Is output. The other functions of the control unit 4 are the same as those of the first embodiment, and thus repeated description is avoided.

  Since the high-frequency component of the DC voltage Vdc appears in the voltage VL2 of the reactor L2, the d-axis voltage command Vd * can be increased as the high-frequency component of the DC voltage Vdc is higher in the second embodiment as well. Therefore, the high frequency component of the DC voltage Vdc can be reduced. Since the correction is performed only on the d-axis voltage command as in the first embodiment, this control method can also be applied to the rotating machine M1 having no saliency. Similarly to the first embodiment, the effect of reducing the high frequency is higher than when correction is performed only on the q-axis voltage command.

  In the illustration of FIG. 7, although the reactor L2 is provided on the input side of the rectifying unit 1, as illustrated in FIG. 8, the reactor L1 is connected to the DC line LH or the DC line LL (DC line LH in FIG. 8). It may be provided. Also in this case, since the high frequency component of the DC voltage Vdc of the capacitor C1 appears in the voltage VL1 of the reactor L1, the voltage detection unit 61 detects the voltage VL1 of the reactor L1 and acquires the high frequency component in more detail. The high frequency component acquisition unit 45 may extract the high frequency component from the voltage VL1 of the reactor L1.

Third embodiment.
In the third embodiment, the rectifying unit 1 inputs a three-phase AC voltage. For example, as illustrated in FIG. 9, the rectifier 1 is a three-phase diode rectifier circuit. The other points are the same as those of the power conversion device of FIG. 3, and the configuration of the control unit 4 is the same as that of the first embodiment.

  Note that the cutoff frequency of the LPF unit 451 can be set in the same manner as in the first embodiment. However, assuming that the frequency of the three-phase AC voltage is 50 Hz, the frequency of the pulsation of the DC voltage Vdc by full-wave rectification is 300 Hz. Therefore, the cutoff frequency of the LPF unit 451 is set so that the 300 Hz frequency component of the DC voltage Vdc can be sufficiently passed. Further, assuming that the resonance frequency of the capacitor C1 and the reactor L1 is about 951 Hz, the cutoff frequency is set so that the frequency component of 951 Hz can be sufficiently cut off. For example, the cutoff frequency can be set to about 430 Hz as in the first embodiment.

  Also in the third embodiment, as in the first embodiment, the higher the high frequency component of the DC voltage Vdc, the higher the d-axis voltage command Vd *, so that the high frequency component of the DC voltage Vdc can be reduced.

  FIG. 10 shows the DC voltage Vdc of the capacitor C1, the one-phase alternating current flowing through the input line of the rectifying unit 1, and the one-phase alternating current output by the power conversion unit 3. In FIG. 10, a 6 kW synchronous machine is adopted as the rotating machine M1, and the wiring inductance and the wiring resistance are set to 0.4572 mH and 0.05125Ω, respectively, as the power supply impedance. In FIG. 10, the waveform of the DC voltage Vdc is indicated by a solid line, the one-phase AC current input to the rectifying unit 1 is indicated by a broken line, and the one-phase AC current output from the power conversion unit 3 is indicated by a two-point difference line. ing.

  For comparison, when the voltage command is not corrected, the DC voltage Vdc of the capacitor C1, the one-phase AC current flowing through the input line of the rectifier 1, and the one-phase output from the power converter 3 The alternating current is shown in FIG. In FIG. 11, the same conditions as those in FIG. 10 are adopted except for the presence or absence of correction.

  From the comparison between FIG. 10 and FIG. 11, when this control method is implemented, the high frequency component (for example, resonance frequency component) of the waveform of the DC voltage Vdc is reduced, and the effect of realizing a stable DC voltage Vdc can be confirmed. . Further, by reducing the high frequency component of the DC voltage Vdc, the high frequency component of the alternating current input to the rectifying unit 1 is also reduced. Furthermore, the peak of the DC voltage Vdc is also reduced with the reduction of the high frequency component. In the first embodiment, the peak of the DC voltage Vdc is slightly reduced (FIGS. 4 and 5).

  Since the d-axis voltage command Vd ** is corrected, the high frequency component of the DC voltage Vdc can be reduced even when the rotating machine M1 has no saliency as in the first embodiment. In addition, the high-frequency component reduction effect is higher than when only the q-axis voltage command Vq * is corrected.

  Also in the third embodiment, similarly to the first embodiment, the reactor does not need to be provided on the DC line LH or the DC line LL, and may be provided on the input line input to the rectifying unit 1. good. However, since a three-phase AC voltage is input to the rectifying unit 1, it is desirable that a reactor is provided for each of the three input lines.

  Similarly to the second embodiment, for example, as shown in FIG. 12, the voltage detection unit 6 may detect the voltage VL1 of the reactor L1 and output it to the control unit 4. In this case, the high frequency component acquisition unit 45 of the control unit 4 extracts the high frequency component of the voltage VL1, and the correction unit 46 increases the d-axis voltage command Vd * as the high frequency component increases.

  Also, when a reactor is provided on the input line of the rectifying unit 1, the voltage of the reactor is detected, the high frequency component of this voltage is extracted, and the d-axis voltage command Vd * is similarly increased based on the high frequency component. Also good.

DESCRIPTION OF SYMBOLS 1 Rectification part 3 Power conversion part 5,6 Voltage detection part 45 High frequency component acquisition part 46 Correction part 47 PWM control part 48 Voltage command generation part

Claims (4)

A rectification unit (1) that full-wave rectifies an N-phase AC voltage input via an input line and outputs a DC voltage between the first and second DC lines (LH, LL). When,
Based on an input control signal, the DC voltage is converted into an AC voltage, and a power converter (2) that outputs the AC voltage to a rotating machine (M1), a control device for a power converter,
A high frequency component acquisition unit (45) for acquiring a high frequency component of the DC voltage higher than 2N times the frequency of the N-phase AC voltage;
In the dq-axis rotation coordinate that rotates in accordance with the rotation of the rotating machine and has a d-axis in phase with the pole center of the field of the rotating machine and a q-axis whose phase is orthogonal to the d-axis, the AC voltage A command generator (48) for generating a d-axis voltage command (Vd **) for the d-axis voltage component and a q-axis voltage command (Vq *) for the q-axis voltage component;
A correction unit (46) that performs correction to increase only the d-axis voltage command as the high-frequency component is higher, and generates a corrected d-axis voltage command (Vd *);
A control device for a power converter, comprising: a control signal generation unit (47) that outputs the control signal to the power converter based on the corrected d-axis voltage command and the q-axis voltage command. A capacitor provided between the first and second DC lines;
A voltage detector (5) for detecting the DC voltage of the capacitor,
The control device for a power converter according to claim 1, wherein the high-frequency component acquisition unit (45) extracts the high-frequency component from the DC voltage of the capacitor. A capacitor (C1) provided between the first and second DC lines;
A reactor (L1) provided on the first or second DC line (LH, LL) on the rectifying unit (1) side of the capacitor;
A reactor voltage detector (6) for detecting a voltage (VL1) applied to the reactor,
The control device for a power converter according to claim 1, wherein the high-frequency component acquisition unit (45) extracts the high-frequency component from the voltage. A reactor (L2) provided in the input line;
Reactor voltage detector (6) for detecting the voltage (VL2) applied to the reactor,
The control device for a power converter according to claim 1, wherein the high-frequency component acquisition unit (45) extracts the high-frequency component from the voltage.

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