TWI467902B - Improvement of Output Current Waveform of Current Control Type Power Converter and Current Control Type Power Converter - Google Patents

Description

Method for improving output current waveform of current control type power converter and current control type power converter

The present invention relates to a current control type power converter and a method of improving an output current waveform of a current control type power converter for improving distortion of an output current waveform of the converter.

A conventional technique of a three-phase, four-wire voltage-controlled power converter is disclosed in Japanese Laid-Open Patent Publication No. 2000-224862 (Patent Document 1). In the voltage control type power converter, a pair of capacitors connected in series are provided between a pair of DC output terminals of a DC power source, and a connection point of a pair of capacitors is formed into a neutral phase.

In addition, the three-phase four-wire voltage-controlled power converter shown in Japanese Laid-Open Patent Publication No. 2007-274825 (Patent Document 2) is configured to connect two sets of semiconductor switching elements in series to a three-phase power converter. The neutral phase arm is additionally provided with a reactor in which one end is connected to the intermediate point of the neutral phase arm and the other end is taken out as a neutral line. The neutral phase arm is alternately switched with a duty of 50%. The third harmonic is then cancelled by PWM control of the switching element of the neutral phase arm.

(Patent Document 1) Japanese Patent Laid-Open Publication No. 2000-224862

(Patent Document 2) Japanese Patent Laid-Open Publication No. 2007-274825

In the former three-phase four-wire voltage-controlled power converter, a large distortion occurs in the output current waveform. Further, in the latter voltage-controlled power converter, although the output voltage waveform distortion is small, it is necessary to provide a neutral phase arm and to perform PWM control on the neutral phase arm, which is complicated. Further, the conventional voltage-controlled power converter controls the output voltage to a constant power converter, and thus it is difficult to actively improve the distortion of the output current waveform. Among them, this problem is a problem that occurs in a current-controlled power converter in which a multi-phase inverter circuit is used and a connection point of a pair of capacitors is a neutral phase.

It is an object of the present invention to provide a method for improving an output current waveform of a current control type power converter and a current control type power converter which can improve distortion of an output current waveform.

A current control type power converter according to the present invention is characterized in that: a pair of capacitors connected in series between a pair of DC output terminals of a DC power supply; and a plurality of opposite phase circuit circuits connected to a pair of DC output terminals; And a current command signal generating circuit for generating a multi-phase current command signal for multi-phase inverter circuit feedback control, forming a connection point of the pair of capacitors into a neutral phase. The current command signal generating circuit includes: a third harmonic voltage component forming unit that generates a third harmonic voltage component that is synchronized with the phase voltage of the multiphase according to the multiphase output voltage of the multiphase inverter circuit; And outputting a harmonic shifting portion of the third harmonic voltage component obtained by shifting the third harmonic voltage component in a direction delayed in time by a predetermined time; and a multi-phase current command signal The subtraction signal obtained by multiplying the predetermined third gain by the shifted third harmonic voltage component is respectively formed, and is formed as a multi-phase divided current command signal and output to the signal subtraction unit of the multi-phase inverter circuit.

In a specific three-phase four-wire current control type power converter, a pair of capacitors, a three-phase inverter circuit, and a current command signal generating circuit that are connected in series between a pair of DC output terminals of a DC power supply are provided. And the gate signal generation circuit. The three-phase inverter circuit includes six bridged semiconductor switching elements and is connected to a pair of DC output terminals of the DC power supply. In addition, the current command signal generating circuit generates a current command signal for three-phase division of the six semiconductor switching elements for feedback control. In addition, the gate signal generating circuit generates a gate signal for PWM control of the six semiconductor switching elements according to the three-phase current command signal. In this current control type power converter, a connection point of a pair of capacitors is formed into a neutral phase.

The inventors of the present invention found that the reason why the waveform of the output current is largely distorted by the three-phase four-wire current-controlled power converter is the third harmonic current component included in the output current. The inventor has thought of removing the third harmonic included in the output current by providing a current command signal to the gate circuit that corrects the corrected three-phase current component of the third harmonic current component included in the output current. The technical idea of the wave component has been confirmed to have an effect.

Therefore, in the specific configuration of the present invention, the current command signal generating circuit is constituted by the third harmonic voltage component forming portion, the wave shifting portions, and the signal subtracting portion. The third harmonic voltage component forming unit generates a third harmonic voltage component that is synchronized with all of the three-phase phase voltages based on the three-phase output voltage of the three-phase inverter circuit. Further, the harmonic shifting unit outputs a third harmonic voltage component obtained by shifting the third harmonic voltage component by a predetermined time in a direction delayed in time.

In addition, the signal subtraction unit subtracts the subtraction signal obtained by multiplying the predetermined third gain of the shifted third harmonic voltage component by the three-phase current command signal, and forms a three-phase corrected current command signal. And output to the gate signal generating circuit. The subtraction signal is the cause component of the third harmonic current component included in the output current. Therefore, if the three-phase divided corrected current command signal obtained by subtracting the subtraction signal from the three-phase current command signal is generated by the gate signal generating circuit, the gate signal is generated by the three-phase inverter circuit. The output three-phase output current waveform does not contain harmonic components. Therefore, the distortion of the output current waveform can be improved by the current control type power converter of the present invention. The technical idea of the present invention is applicable to a current control type power converter in which a connection point of a pair of capacitors is formed into a neutral phase.

The "predetermined time" and the "predetermined gain" described above are set so as to suppress the occurrence of distortion of the current waveform of the third harmonic current component in the multiphase output current of the multi-phase inverter circuit. The "predetermined time" and the "predetermined gain" are obtained by analyzing the output of the third harmonic current from the output current waveform of the conventional current-controlled power converter to which the present invention is not applied, according to the third harmonic The waveform of the wave current component can be set. Specifically, the predetermined time corresponds to the time delay component of the third harmonic current component included in the multiphase output current with respect to the multiphase output voltage. Further, the predetermined gain is set such that the amplitude of the shifted third harmonic voltage component matches the amplitude of the third harmonic component included in the multiphase output current. In this way, the distortion of the output current waveform can be improved with higher precision.

The present invention can also be grasped as a method for improving the waveform distortion of the multi-phase output current in the above current-controlled power converter. That is, in the method of the present invention, the waveform of the multi-phase output current is improved by correcting the multi-phase current command signal to remove the third harmonic component included in the multi-phase output current. distortion.

In a specific method for a three-phase four-wire current-controlled power converter, first, based on a three-phase output voltage of a three-phase inverter circuit, a phase voltage of three phases is used to synchronize with a phase voltage of three phases. 3rd harmonic voltage component. Then, the phase of the third harmonic voltage component is delayed in time so that the phase of the third harmonic voltage component matches the phase of the third harmonic component included in the three-phase output current. The third harmonic voltage component after shifting. Further, the third harmonic of the shift is multiplied by a predetermined gain in which the amplitude of the shifted third harmonic voltage component coincides with the amplitude of the third harmonic current component included in the three-phase output current. The voltage component forms a subtraction signal. Then, the current-command signal of the three-phase sub-divided signal is respectively reduced to form a three-phase corrected current command signal, and is output to the gate signal generating circuit. As a result, since the third-order output current waveform does not include the third harmonic current component, the distortion of the output current waveform can be improved.

According to the current-controlled power converter of the present invention, the multi-phase divided current command signal is removed to the multi-phase divided corrected current command signal after the signal causing the third harmonic component is generated, and the current command signal is input to the gate signal. Since the circuit is generated, the output current of the multi-phase inverter circuit can obtain an output current waveform that does not substantially include the third harmonic current component.

Embodiments of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a circuit diagram showing a configuration of an embodiment of a current control type power converter according to the present invention, and Fig. 2 is a view showing an example of a configuration of a current command signal generating circuit and a gate signal generating circuit. The three-phase four-wire current control type power converter shown in Fig. 1 includes a pair of capacitors C1 and C2 connected in series between a pair of DC output terminals of the DC power source DC. Further, a three-phase inverter circuit IV is connected between the pair of DC output terminals. The three-phase inverter circuit IV is configured to include six bridged semiconductor switching elements Tr1 to Tr6 and six diodes D1 to D6 connected in anti-parallel with the six semiconductor switching elements Tr1 to Tr6. The three output terminals of the three-phase inverter circuit IV are connected to the three-phase AC line of the AC source AC through the reactors L1 to L3, respectively. Further, a connection point of the pair of capacitors C1 and C2 is connected to a neutral phase line of the AC source AC. Capacitors C3 to C5 are connected between the three-phase AC line and the neutral phase line, respectively. Next, the current command signal generating circuit 1 generates a three-phase current command signal for feedback control of the six semiconductor switching elements Tr1 to Tr6. Further, the gate signal generating circuit 2 generates a gate signal for PWM control of the six semiconductor switching elements Tr1 to Tr6 based on the three-phase current command signal.

As shown in FIG. 2, the current command signal generating circuit 1 of the present embodiment includes a third harmonic voltage component generating unit 3, a harmonic shifting unit 4, and a signal subtracting unit 5. The three-phase AC output current detected by the three current detectors CT1 to CT3 is input to the current command signal generating circuit 1 and the output voltage from the three-phase AC output line is input (U-phase voltage, V phase voltage, W phase voltage). Further, the voltage of the neutral phase line is input to the current command signal generating circuit 1 as a reference point of 0 V when the phase voltage waveforms Vu, Vv, and Vw of the three phases are detected and controlled. Among them, a neutral phase line is not shown in FIG. 2 .

As shown in Fig. 2, the third harmonic voltage component creating unit 3 creates a third harmonic which is synchronized with the three-phase phase voltage waveforms Vu, Vv, and Vw based on the three-phase output voltage of the three-phase inverter circuit IV. Wave voltage component. Fig. 3 shows the third harmonic voltage component V3 when the phase voltage waveform Vu is used as a reference. For the three-phase phase voltage waveforms Vu, Vv, and Vw, there is only one third harmonic voltage component V3. Therefore, the phase difference between the phase of the third harmonic voltage component V3 and the phase of the three-phase phase voltage waveforms Vu, Vv, and Vw is different.

The harmonic shifting unit 4 shifts the generated third harmonic voltage component V3 by a predetermined time Δt in the temporally delayed direction, and outputs a shifted third harmonic voltage component V3. ,. In addition, the method of creating the third harmonic voltage component in the third harmonic voltage component forming unit 3 is well known, and thus the description thereof is omitted. Signal reduction unit 5 is made by feedback control The three-phase current command signal Iu_ref~Iw_ref is used to subtract a predetermined subtraction signal ΔI3 obtained by multiplying the shifted third harmonic voltage component V3' by a predetermined gain K1 to form a three-phase component. The corrected current command signal Iux~Iwx is output to the gate signal generating circuit 2. Fig. 3 is a diagram showing the third harmonic voltage component V3' multiplied by the gain K1 obtained by shifting the third harmonic voltage component V3 with the phase voltage waveform Vu as a reference for a predetermined time Δt. The subtraction signal △I3. The predetermined gain K1 is set such that the amplitude of the shifted third harmonic voltage component V3 coincides with the amplitude of the third harmonic current component included in the three-phase output current. The gain K1 is also set in advance as a fixed value. However, if the gain K1 is excessively increased, the phase relationship between the current command signal and the corrected current command signal deviates. Therefore, in the present embodiment, the gain K1 is formed to a small extent that the phase relationship does not deviate. Value (for example, a value below 0.02).

Here, the predetermined time Δt in the harmonic shifting section 4 and the predetermined gain K1 in the signal subtracting section 5 are such as to suppress the occurrence of the three-phase output current in the three-phase inverter circuit IV according to the third harmonic current component. The current waveform distortion is set separately. The specific predetermined time Δt and the predetermined gain K1 can be extracted, and the third harmonic current component is extracted from the output current waveform of the conventional current control type power converter to which the present invention is not applied, according to the first The waveform of the third harmonic current component is set in advance. The third harmonic current component is included in each of the three-phase output currents in the same phase. Further, specifically, the predetermined time Δt corresponds to the time delay of the third harmonic current component included in the three-phase output current with respect to the three-phase output voltage. Generally, the predetermined time Δt is set in advance with a fixed value of 1 msec to 10 msec.

In the present embodiment, the current command signals Iu_ref to Iw_ref of the three-phase points used for the feedback control are current command signals (U-phase current commands) of the respective phases outputted from the current command generating means (not shown). The signal, the V-phase current command signal, and the W-phase current command signal are subtracted from the signal obtained by multiplying the signal obtained by the U-phase current to the W-phase current detected by the current detectors CT1 to CT3 by the gain K2, and adding the U-phase voltage. ~W phase voltage derived. When the three-phase current command signals Iu_ref~Iw_ref used for the feedback control are obtained, the U-phase voltage to the W-phase voltage are added in order to synchronize the output phase current with the output phase voltage.

A subtraction signal ΔI3 is a causative component of the third harmonic component included in the three-phase output current. Therefore, the three-phase divided current command signal Iux~Iwx obtained by subtracting the subtraction signal ΔI3 from the three-phase current command signal Iu_ref~Iw_ref is used, and the gate signal generating circuit 2 is required to generate the gate for PWM control. Signals Su, XSu, Sv, XSv, Sw, XSw. The gate signal generating circuit 2 uses the comparator CMP to compare the carrier outputted by the carrier generator 6 with the current command signals Iux~Iwx to generate the gate signals Su, XSu, Sv, XSv required for the PWM control signals. , Sw, XSw. In the gate signal generating circuit 2, a dead time for causing the gate signal Su and the gate signal Xsu not to simultaneously turn on a pair of semiconductor switching elements is added to the two signals. between. Further, in the gate signal generating circuit 2, the insulation between the gate signals is performed, and the gate signals are supplied to the respective semiconductor switching elements Tr1 to Tr6.

In the method of the present invention, the three-phase current command signals Iu_ref~Iw_ref are corrected in such a manner as to remove the third harmonic component included in the three-phase output current, thereby improving the waveform distortion of the three-phase output current. Therefore, according to the three-phase output voltage of the three-phase inverter circuit, a third harmonic voltage component V3 synchronized with the phase voltage of the three phases is formed. Next, the third harmonic voltage component V3 is delayed in time so that the phase of the third harmonic voltage component V3 coincides with the phase of the third harmonic current component included in the three-phase output current. The direction shifts to form the shifted third harmonic voltage component V3'. Further, the predetermined gain K1 in which the amplitude of the shifted third harmonic voltage component V3' coincides with the amplitude of the third harmonic current component included in the three-phase output current is multiplied by the shifted The third harmonic voltage component V3' forms a subtraction signal ΔI3. Then, the subtraction signal ΔI3 is finally subtracted from the three-phase current command signals Iu_ref~Iw_ref to form three-phase corrected current command signals Iux~Iwx, and output to the gate signal generating circuit 2. As a result, the third-order output current waveform does not include the third harmonic current component, so that the distortion of the output current waveform can be improved.

In the above embodiment, the three-phase four-wire current control type power converter is targeted, but the present invention is applicable to a current using a plurality of opposite phase circuit circuits and a connection point of a pair of capacitors as a neutral phase. Controlled power converter.

1. . . Current command signal generation circuit

2. . . Gate signal generation circuit

3. . . The third harmonic voltage component creation unit

4. . . Harmonic shifting section

5. . . Signal reduction department

6. . . Carrier generator

AC. . . Commercial AC power supply (AC source)

C1~C5. . . Capacitor

CMP. . . Comparators

CT1~CT3. . . Current detector

D1~D6. . . Dipole

DC. . . DC power supply

Iux~Iwx. . . Current command signal

Iu_ref~Iw_ref. . . Current command signal

K1, K2. . . Gain

L1~L3. . . Reactor

Su, XSu, Sv, XSv, Sw, XSw. . . Gate signal

Tr1~Tr6. . . Semiconductor switching element

V3, V3’. . . Third harmonic voltage component

Vu, Vv, Vw. . . Phase voltage waveform

ΔI3. . . Subtraction signal

Fig. 1 is a circuit diagram showing a configuration of an embodiment of a current control type power converter according to the present invention.

Fig. 2 is a view showing an example of the configuration of a current command signal generating circuit and a gate signal generating circuit.

Fig. 3 is a waveform diagram showing an example of one phase voltage waveform, third harmonic voltage component, and subtraction signal.

1. . . Current command signal generation circuit

2. . . Gate signal generation circuit

3. . . The third harmonic voltage component creation unit

4. . . Harmonic shifting section

5. . . Signal reduction department

6. . . Carrier generator

CMP. . . Comparators

Iux~Iwx. . . Current command signal

Iu_ref~Iw_ref. . . Current command signal

K1, K2. . . Gain

Su, XSu, Sv, XSv, Sw, XSw. . . Gate signal

V3, V3’. . . Third harmonic voltage component

Vu, Vv, Vw. . . Phase voltage waveform

ΔI3. . . Subtraction signal

Claims (4)

A current control type power converter comprising: a pair of capacitors connected in series between a pair of DC output terminals of a DC power supply; and comprising six bridged semiconductor switching elements and connected to the pair of DC outputs a three-phase inverter circuit of the terminal; a current command signal generating circuit for generating a three-phase current command signal for feedback control of the six semiconductor switching elements; and a current command signal according to the three-phase component a current control type power converter in which a gate signal of the gate signal is PWM-controlled by the six semiconductor switching elements, and a connection point of the pair of capacitors is formed as a neutral phase, wherein the current is The command signal generating circuit includes: a third harmonic voltage component generating unit that generates a third harmonic voltage component synchronized with a phase voltage of the three phases based on a three-phase output voltage of the three-phase inverter circuit; The third harmonic voltage obtained by shifting the third harmonic voltage component in a direction delayed in time by a predetermined time is outputted a harmonic shifting portion; and a subtraction signal obtained by multiplying the predetermined third gain of the shifted third harmonic voltage component by the current command signal of the three-phase component, and forming a three-phase correction The subsequent current command signal is output to the signal subtraction unit of the gate signal generating circuit. The current control type power converter according to claim 1, wherein the predetermined time and the predetermined gain are used to suppress generation of a three-phase output current of the three-phase inverter circuit according to a third harmonic current component. The way in which the current waveform is distorted is set separately. The current control type power converter according to claim 1, wherein the predetermined time period corresponds to a time delay of a third harmonic current component included in the three-phase output current with respect to the three-phase output voltage The predetermined gain is set such that the amplitude of the third harmonic voltage component after the shift matches the amplitude of the third harmonic current component included in the three-phase output current. A method for improving an output current waveform of a current control type power converter is a method for improving waveform distortion of a three-phase output current output by a current control type power converter, the current control type power converter having: a pair of capacitors connected in series between a pair of DC output terminals of a DC power supply; a three-phase inverter circuit comprising six bridged semiconductor switching elements and connected to the pair of DC output terminals; 6 semiconductor switching elements for feedback control of the current command signal generating circuit of the three-phase current command signal; and generating a gate for PWM control of the six semiconductor switching elements according to the current command signal of the three-phase component The gate signal generating circuit of the pole signal, and the connection point of the pair of capacitors is formed into a neutral phase, and its characteristics a third harmonic voltage component synchronized with a phase voltage of the three phases according to the three-phase output voltage of the three-phase inverter circuit, so that the phase of the third harmonic voltage component and the three-phase output current are The third harmonic voltage component obtained by shifting the direction in which the third harmonic voltage component is delayed in time is formed so that the phases of the third harmonic current components are matched. a predetermined gain in which the amplitude of the third harmonic voltage component after the shift is matched with the amplitude of the third harmonic current component included in the three-phase output current, and the third gain after the shift The subharmonic voltage component is multiplied to form an subtraction signal, and the subtraction signal is subtracted from the three-phase current command signal to form a three-phase corrected current command signal and output to the gate signal. Circuit.