JP5833524B2 - Power converter and control device for power converter - Google Patents

Description

  The present invention relates to a power conversion device and a control device for the power conversion device. The present invention particularly relates to an improvement in voltage utilization in a three-phase half-bridge PWM (pulse width modulation) power converter.

  In a three-phase PWM converter that converts alternating current to direct current or a PWM inverter that converts direct current to alternating current, a third order that is offset by the line voltage is provided on condition that the line voltage of the output alternating voltage is maintained as a sine wave. A method of generating a voltage command value for each phase arm by superimposing a harmonic component that is an integral multiple of a sine wave voltage command value is proposed. According to this method, the voltage utilization rate is improved as compared with the sine wave modulation method. For example, a control device for a power conversion device disclosed in Japanese Patent Application Laid-Open No. 10-1664846 (Patent Document 1) includes a zero-phase modulator for superimposing a third-order integral multiple of harmonics on the output of a current control amplifier. Prepare.

  FIG. 4 is a functional block diagram of a conventional converter control circuit disclosed in JP-A-10-164846. Referring to FIG. 4, AC power from three-phase AC power supply 201 is converted into DC power by converter 204. AC capacitor 202 and reactor 203 constitute a filter circuit that removes harmonics. Converter 204 includes a power semiconductor (not shown) and converts AC power into DC power. The DC power from the converter 204 is smoothed by the DC smoothing capacitor 205 and supplied to a load (not shown).

  The voltage sensor 207 detects the voltage of the three-phase AC power source 201. The voltage sensor 208 detects the DC voltage of the DC smoothing capacitor 205. Current sensor 209 detects current Ic input to converter 204.

  FIG. 5 is a diagram showing a configuration example of converter 204 shown in FIG. Referring to FIG. 5, converter 204 is, for example, a three-phase full-bridge conversion circuit, and includes a power semiconductor (Qu to Qz) such as an IGBT (Insulated Gate Bipolar Transistor). Corresponding to each of the three phases, AC capacitors 202u, 202v, and 202w are provided, and reactors 203u, 203v, and 203w are provided. DC smoothing capacitors 205p and 205n are connected in series between the positive electrode line Pdc and the negative electrode line Ndc.

  Returning to FIG. 4, the operation of the converter control circuit will be described. The DC voltage setting circuit 210 outputs a DC voltage reference Vdc *. The subtractor 11 calculates a deviation between the DC voltage reference Vdc * and the detected value Vdc− of the DC voltage Vdc detected by the voltage sensor 8. The deviation calculated by the subtractor 11 is input to the voltage controller (AVR) 212.

  The multiplier 213 calculates the product of the output of the voltage controller 212 and the AC power supply voltage detected by the voltage sensor 208 for each of the three-phase AC phases. Thus, the multiplier 213 generates a sine wave three-phase current command (Icu *, Icv *, Icw *). The subtractor 214 receives the current command value (Icu * to Icw *) and the detected current value (Icu−, Icv−, Icw−) detected by the current sensor 209, and detects the current command value and detection for each phase. Calculate the deviation between the values. The deviation of each phase is input to a current controller (ACR) 215 for each phase.

  The adder 217 adds the output of the current controller 215 for each phase and the voltage command from the zero-phase voltage command generation circuit 216 to obtain a three-phase PWM voltage command value (Vu *, Vv *, Vw *). Is generated. The voltage command values (Vu * to Vw *) are input to the PWM circuit 218. The PWM circuit 218 generates a gate pulse signal for turning on and off the power semiconductor in the converter 204 according to a known method such as a triangular wave carrier comparison method, and outputs the gate pulse signal to the converter 204.

Here, the zero-phase voltage command value is a harmonic of the third integer multiple of the basic sine wave voltage command from the current controller (ACR) 215. When the amplitude of the triangular wave carrier of the PWM circuit is ± Vc and the modulation factor is a, the zero-phase voltage command value is expressed by the following equation: Zero-phase voltage command value = 2 / √3a · Vc · 1/6 · sin ( 3θ) (1)
θ: Fundamental wave reference phase synchronized with the power supply voltage of the AC power supply The amplitude of sinθ is 1, whereas the maximum value of sinθ + (1/6) · sin (3θ) is 3 ^1/2 / 2. The maximum value of the zero-phase voltage command value is a · Vc. PWM is possible in the range of 0 ≦ a ≦ 1. The peak voltage of the PWM voltage command value is lowered by superimposing the zero phase voltage command. Therefore, the voltage utilization factor can be improved by (3 ^1/2 / 2-1) × 100 = about 15% compared to the case where no zero-phase voltage is superimposed.

  In addition, since the zero-phase voltage command value is a third-order integral multiple of the fundamental wave, the line voltage does not include the third-order harmonic voltage. Therefore, the line voltage can be maintained as a sine wave.

Japanese Patent Laid-Open No. 10-164846

  In the case of the above configuration, the current command value Ic * for each phase is a sine wave. Assuming that the output of the voltage controller (AVR) 212 is A, the current command value Ic * of each phase is expressed by the following equation.

Icu * = A × √2 × Vs × sin (θ) (2)
Icv * = A × √2 × Vs × sin (θ−2 / 3π) (3)
Icw * = A × √2 × Vs × sin (θ + 2 / 3π) (4)
Therefore, as shown in the following equation, the current command does not include the zero phase component.

Icu * + Icv * + Icw * = 0 (5)
Here, the configuration shown in FIG. 4 superimposes the zero-phase voltage command on the current command value by feedforward. This configuration and control method can be applied only when the zero-phase current does not flow to the converter circuit even when the zero-phase voltage is output. That is, the above method is applicable only to the full bridge circuit shown in FIG.

  On the other hand, the full bridge circuit generates a common mode voltage, which causes an increase in leakage current that causes noise. For this reason, a three-phase half-bridge circuit may be applied as a converter circuit for suppressing the common mode voltage.

  FIG. 6 is a diagram illustrating a configuration example of a three-phase half-bridge circuit. Referring to FIG. 6, the same parts as those in FIG. In the configuration shown in FIG. 6, the neutral phase that is the connection point of the AC capacitors 202 u to 202 w is connected to the neutral point that is the connection point of the DC smoothing capacitors 205 p and 205 n via the neutral phase line 206. This is different from the configuration shown in FIG.

  As described above, in the three-phase half-bridge circuit, the neutral phase of the AC filter and the neutral point of the DC circuit (DC smoothing capacitors 205p and 205n) are connected. Thus, a closed circuit is formed. For this reason, when the above control method is applied, a zero-phase current component flows through the route of converter 204 -AC filter-neutral phase line 206 -DC smoothing capacitor 205 due to the zero-phase voltage.

  Therefore, when the conventional control method is applied to a three-phase half-bridge circuit, the above equation (5) is not satisfied, and thus current according to the current command does not flow. As a result, there is a problem that the converter cannot be controlled. Alternatively, since the converter is controlled so that the zero-phase component current becomes zero, the current control works so as to cancel the zero-phase voltage superimposed by feedforward. Therefore, there is a problem that the voltage utilization rate does not increase.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to improve voltage utilization in a half-bridge type power converter.

  In one aspect of the present invention, power conversion device 100 includes a converter that converts power between three-phase alternating current and direct current, and a reactor and a capacitor provided for each phase of the three-phase alternating current, and is generated from the converter. DC circuit having a connection point connected to the neutral phase of the filter circuit, including a filter circuit for removing harmonics to be generated, and a plurality of capacitors connected in series between a positive electrode and a negative electrode on the DC side of the converter And a control circuit for controlling the converter. The control circuit generates a sinusoidal three-phase current command value based on a deviation between the DC voltage reference value and the detected DC voltage value of the converter and a three-phase AC voltage. Generation circuit, zero-phase current command generation circuit that generates a harmonic current value that is an integer multiple of the third order as the zero-phase current command value, and adds the zero-phase current command value to the three-phase current command value for conversion Current controller that generates a three-phase PWM voltage command value based on the deviation between the current command value from the adder and the detected value of the three-phase AC current of the converter And a PWM circuit that generates a control signal for PWM control of the converter based on the PWM voltage command value.

  In another aspect of the present invention, a control device for a power converter is provided. A power converter includes a converter that converts power between three-phase AC and DC, and a reactor and a capacitor provided for each phase of the three-phase AC, and a filter circuit that removes harmonics generated from the converter And a DC circuit including a plurality of capacitors connected in series between a positive electrode and a negative electrode on the DC side of the converter, and having a connection point connected to the neutral phase of the filter circuit. The control device generates a sine wave three-phase current command value based on a deviation between the DC voltage reference value and the detected DC voltage value of the converter and a three-phase AC voltage. Generation circuit, zero-phase current command generation circuit that generates a harmonic current value that is an integer multiple of the third order as the zero-phase current command value, and adds the zero-phase current command value to the three-phase current command value for conversion Current controller that generates a three-phase PWM voltage command value based on the deviation between the current command value from the adder and the detected value of the three-phase AC current of the converter And a PWM circuit for generating a control signal for PWM control of the converter based on the PWM voltage command value.

  ADVANTAGE OF THE INVENTION According to this invention, a voltage utilization factor can be improved in a half bridge type PWM power converter.

It is a schematic block diagram of the power converter device which concerns on embodiment of this invention. It is a functional block diagram of the control circuit which concerns on Embodiment 1 of this invention. It is a functional block diagram of the control circuit which concerns on Embodiment 2 of this invention. It is a functional block diagram of the conventional converter control circuit disclosed by Unexamined-Japanese-Patent No. 10-164846. It is the figure which showed the structural example of the converter shown by FIG. It is the figure which showed the structural example of the three-phase half bridge circuit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic configuration diagram of a power conversion device according to an embodiment of the present invention. Referring to FIG. 1, the power converter includes AC capacitors 2u, 2v, 2w, reactors 3u, 3v, 3w, converter 4, DC smoothing capacitors 5p, 5n, neutral phase line 6, and control circuit. 50.

  Converter 4 converts the three-phase alternating current from three-phase alternating current power supply 1 into direct-current power. The DC power output from the converter 4 is supplied to a load (not shown), for example.

  The converter 4 includes power semiconductors Qu, Qx, Qv, Qy, Qw, Qz such as IGBT. Power semiconductors Qu and Qx are connected in series between positive electrode line Pdc and negative electrode line Ndc to form a U-phase arm. Power semiconductors Qv and Qy are connected in series between positive electrode line Pdc and negative electrode line Ndc to form a V-phase arm. Power semiconductors Qz and Qw are connected in series between positive electrode line Pdc and negative electrode line Ndc to form a W-phase arm.

  AC capacitors 2u, 2v, and 2w and reactors 3u, 3v, and 3w constitute a filter circuit, and remove harmonic components generated from converter 4. One end of reactor 3u is connected to a connection point of power semiconductors Qu and Qx via an AC line corresponding to the U phase. The other end of reactor 3u is connected to an AC line on the three-phase AC power source 1 side. One end of reactor 3v is connected to a connection point of power semiconductors Qv and Qy via an AC line corresponding to the V phase. The other end of the reactor 3v is connected to an AC line on the three-phase AC power source 1 side. Reactor 3w has one end connected to a connection point of power semiconductors Qw and Qz via an AC line corresponding to the W phase. The other end of reactor 3w is connected to an AC line on the three-phase AC power source 1 side.

  One end of AC capacitor 2u is connected to the other end of reactor 3u. One end of AC capacitor 2v is connected to the other end of reactor 3v. One end of AC capacitor 2w is connected to the other end of reactor 3w. The other ends of the AC capacitors 2u, 2v, 2w are connected to each other.

  The DC smoothing capacitors 5p and 5n constitute a DC circuit. DC smoothing capacitors 5p and 5n are directly connected between positive electrode line Pdc and negative electrode line Ndc, and smooth the DC power output from converter 4.

  The neutral phase line 6 connects the neutral phase, which is the connection point of the AC capacitors 2u to 2w, and the neutral point, which is the connection point of the DC smoothing capacitors 5p and 5n. The control circuit 50 controls switching of the power semiconductors Qu, Qx, Qv, Qy, Qw, Qz constituting the converter 4 according to the PWM method. That is, in the embodiment of the present invention, a three-phase half-bridge PWM power converter is realized.

  In the control of the three-phase half-bridge PWM power converter according to the embodiment of the present invention, a current command that is a third integer multiple of the fundamental wave is superimposed on the current command (sine wave current command) of converter 4. Improve voltage utilization. According to the embodiment of the present invention, it is possible to improve the voltage utilization rate of the three-phase half-bridge type PWM power converter without adding new parts. Thereby, a low noise and highly efficient power converter device can be achieved. Hereinafter, the control of the converter according to each embodiment will be described in detail.

[Embodiment 1]
FIG. 2 is a functional block diagram of the control circuit 50 according to the first embodiment of the present invention. Referring to FIG. 2, control circuit 50 includes DC voltage setting circuit 10, subtractor 11, voltage controller (AVR) 12, multiplier 13, subtractor 14, and current controller (ACR) 15. A PWM circuit 18, a zero-phase current command generation circuit 19, and an adder 20. The DC voltage setting circuit 10, the subtractor 11, the voltage controller (AVR) 12, and the multiplier 13 are for generating a sine wave three-phase current command value (Icu *, Icv *, Icw *). A sine wave current command generation circuit 10A is configured. In the figure, “///” is a symbol indicating three phases.

  The DC voltage setting circuit 10 outputs a DC voltage reference Vdc * that is a reference for the DC voltage Vdc between the positive electrode line Pdc and the negative electrode line Ndc. The subtractor 11 calculates a deviation between the DC voltage reference Vdc * and the detected value Vdc− of the DC voltage Vdc detected by the voltage sensor 8. The deviation calculated by the subtractor 11 is input to the voltage controller (AVR) 12.

  The multiplier 13 calculates the product of the output of the voltage controller 12 and the AC power supply voltage Vs− of each phase detected by the voltage sensor 7. Thus, the multiplier 13 generates a sine wave three-phase current command value (Icu *, Icv *, Icw *).

  The zero-phase current command generation circuit 19 generates a zero-phase current command value Ic0 * from the detected value of the power supply voltage Vs detected by the voltage sensor 7. The adder 20 adds the zero-phase current command value Ic0 * to the sine wave three-phase current command values (Icu *, Icv *, Icw *) to generate a current command value.

  The subtractor 14 generates a deviation between the current command from the adder 20 and the detected current value (Icu− to Icw−) detected by the current sensor 9 for each phase, and the current controller 15 for each phase. Enter in (ACR). The output of each phase current controller is input to the PWM circuit 18 as a three-phase PWM voltage command value (Vu *, Vv *, Vw *). The PWM circuit 18 generates a control signal (gate pulse signal) for turning on and off the power semiconductor in the converter 4 according to a known method such as a triangular wave carrier comparison method, and outputs the control signal to the converter 4.

  The zero-phase current command value Ic0 * is added to the sinusoidal three-phase current command values (Icu *, Icv *, Icw *) in order to improve the voltage utilization factor. The zero-phase current command value Ic0 * is a third-order integer multiple harmonic current value determined from a third-order integer multiple harmonic voltage with respect to the basic sine wave voltage and the capacity of the AC capacitor 2. The zero-phase current command generation circuit 19 obtains a zero-phase current command value Ic0 * according to the following equation (6). The zero-phase current command value Ic0 * is a zero-phase current value to the AC capacitor for obtaining the zero-phase voltage value obtained by the equation (1).

Ic0 * = 2 / √3a · Vc · 1/6 · 2π · 3 · f · Cf · cos (3θ) (6)
here,
f: Frequency of power supply voltage Vs Cf: Capacity of AC capacitor.

  Therefore, the current command (Icu *, Icv *, Icw *) of each phase output from the adder 20 is expressed by the following equations (7) to (9) obtained by adding the zero-phase current command to the sine wave current command. Is done. A represents the output of the voltage controller (AVR) 12.

Icu * = A × √2 × Vs × sin (θ) + Ic0 * (7)
Icv * = A × √2 × Vs × sin (θ−2 / 3π) + Ic0 * (8)
Icw * = A × √2 × Vs × sin (θ + 2 / 3π) + Ic0 * (9)
As described above, in the first embodiment, the current command for converter 4 is generated by superimposing the third-order integer multiple harmonic current Ic0 * on the sine wave current command (Icu *, Icv *, Icw *). To do. A third-order integral multiple harmonic current flows through the converter current, and a zero-phase third-order harmonic voltage is superimposed on the AC capacitor 2. Therefore, the phase voltage peak of the AC capacitor 2 is lowered. As a result, the voltage utilization factor can be improved by about 15% compared to the case where no zero-phase voltage is superimposed.

  Furthermore, since the zero-phase current command value is a third-order harmonic, the line voltage does not include the third-order harmonic voltage. Therefore, the line voltage can be maintained as a sine wave.

[Embodiment 2]
In the first embodiment, in order to improve the voltage utilization factor, a zero-phase current command value that generates a required tertiary voltage is obtained by feed-forward addition to a sine wave three-phase current command value. In the second embodiment, control for feeding back a third-order voltage is executed.

  FIG. 3 is a functional block diagram of the control circuit 50 according to the second embodiment of the present invention. 2 and 3, in the second embodiment, instead of the zero-phase current command generation circuit 19, a zero-phase voltage command generation circuit 16, a subtractor 22, a voltage controller (AVR) 23, The difference from Embodiment 1 is that a zero-phase voltage detector 24 is provided.

  The zero-phase voltage command generation circuit 16 generates a zero-phase voltage command value Vs0 * according to the above equation (1). The zero phase voltage detector 24 detects the zero phase voltage Vs0−. Specifically, the zero-phase voltage detector 24 detects the zero-phase voltage Vs0− by adding the detected values of the three-phase phase voltages (shown as Vs−) detected by the voltage sensor 21.

  The subtractor 22 generates a deviation between the zero phase voltage command value Vs0 * and the zero phase voltage Vs0−. This deviation is input to the voltage controller (AVR) 23. Thereby, feedback control is performed. The output of the voltage controller 23 becomes a zero-phase current command for generating a zero-phase voltage for improving the voltage utilization rate. Similarly to the first embodiment, the adder 20 adds the zero-phase current command value to the sine wave three-phase current command (Icu *, Icv *, Icw *). Thereby, it is possible to superimpose a tertiary voltage that improves the voltage utilization rate.

  As described above, in the second embodiment, the control circuit 50 is configured to feedback control the zero phase voltage. As a result, it is possible to superimpose a higher-accuracy tertiary voltage on the voltage command value of the sine wave as compared with the first embodiment.

  In the first and second embodiments, control related to a converter that converts alternating current into direct current is shown. However, the control according to the above embodiment can be applied to an inverter circuit that converts direct current to alternating current instead of the converter. In this case, the same effect as described above can be obtained.

  Further, in the three-phase half-bridge conversion circuit of FIG. 4, the neutral phase that is the connection point of the AC capacitors 2 u to 2 w is shown as a circuit that is connected to the neutral point that is the connection point of the DC smoothing capacitors 5 p and 5 n. However, the neutral phase only needs to be connected at one point of the DC circuit. Therefore, a half bridge circuit in which the neutral phase of the filter circuit is connected by the DC smoothing capacitor 5p or 5n is also applicable to the present invention.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1,201 Three-phase AC power source, 2,2u-2w, 202,202u-202w capacitor, 3u-3w, 203,203u-203w reactor, 4,204 converter, 5p, 5n, 205,205p, 205n DC smoothing capacitor, 6, 206 neutral phase line, 7, 8, 21, 207, 208 voltage sensor, 9, 209 current sensor, 10 DC voltage setting circuit, 10A sine wave current command generation circuit, 11, 14, 22, 214 subtractor, 12, 23, 212 Voltage controller (AVR), 13, 213 multiplier, 15, 215 Current controller (ACR), 16, 216 Zero phase voltage command generation circuit, 18, 218 PWM circuit, 19 Zero phase current command generation Circuit, 20, 217 adder, 24 zero phase voltage detector, 50 control circuit, 100 power converter, Ndc Polar, Pdc positive line, Qu~Qw, Qx~Qz power semiconductor.

Claims (7)

A converter that converts power between three-phase AC and DC;
A filter circuit including a reactor and a capacitor provided for each phase of the three-phase alternating current, and removing harmonics generated from the converter;
A DC circuit including a plurality of capacitors connected in series between a positive electrode and a negative electrode on the DC side of the converter, and having a connection point connected to a neutral phase of the filter circuit;
A control circuit for controlling the converter,
The control circuit includes:
A sine wave current command generation circuit that generates a sine wave three-phase current command value based on a deviation between a DC voltage reference value and a detected value of the DC voltage of the converter and the three-phase AC voltage When,
A zero-phase current command generation circuit that generates a third-order integer multiple harmonic current value as a zero-phase current command value;
An adder for adding the zero-phase current command value to the three-phase current command value to generate a current command value for the converter;
A current controller that generates a three-phase PWM voltage command value based on a deviation between the current command value from the adder and a detected value of the three-phase alternating current of the converter;
And a PWM circuit that generates a control signal for PWM control of the converter based on the PWM voltage command value.   The zero-phase current command generation circuit determines the zero-phase current command value from a harmonic voltage that is a third-order integer multiple of the three-phase alternating current basic sine wave voltage and the capacitance of the capacitor, and The power conversion device according to claim 1, configured to add a phase current command value to the three-phase current command value in a feedforward manner. The zero-phase current command generation circuit is
A zero-phase voltage command generation circuit that generates a zero-phase voltage command value based on the three-phase AC voltage detection value;
A zero-phase voltage detector for detecting the zero-phase voltage of the three-phase AC from the voltage detection value of the three-phase AC;
The power converter according to claim 1, further comprising: a voltage controller that generates the zero-phase current command value from a deviation between the zero-phase voltage command value and the detected value of the zero-phase voltage.   The power converter according to any one of claims 1 to 3, wherein the converter is a converter that converts three-phase alternating current into direct current. A converter that converts power between three-phase AC and DC, a filter circuit that includes a reactor and a capacitor provided for each phase of the three-phase AC, and removes harmonics generated from the converter; A controller for a power converter, comprising: a plurality of capacitors connected in series between a positive electrode and a negative electrode on the DC side of the capacitor; and a DC circuit having a connection point connected to a neutral phase of the filter circuit. There,
A sine wave current command generation circuit that generates a sine wave three-phase current command value based on a deviation between a DC voltage reference value and a detected value of the DC voltage of the converter and the three-phase AC voltage When,
A zero-phase current command generation circuit that generates a third-order integer multiple harmonic current value as a zero-phase current command value;
An adder for adding the zero-phase current command value to the three-phase current command value to generate a current command value for the converter;
A current controller that generates a three-phase PWM voltage command value based on a deviation between the current command value from the adder and a detected value of the three-phase alternating current of the converter;
And a PWM circuit that generates a control signal for PWM control of the converter based on the PWM voltage command value.   The zero-phase current command generation circuit determines the zero-phase current command value from a harmonic voltage that is a third-order integer multiple of the three-phase alternating current basic sine wave voltage and the capacitance of the capacitor, and The control device for a power converter according to claim 5, wherein the control device is configured to add a phase current command value to the three-phase current command value by feedforward. The zero-phase current command generation circuit is
A zero-phase voltage command generation circuit that generates a zero-phase voltage command value based on the three-phase AC voltage detection value;
A zero-phase voltage detector for detecting the zero-phase voltage of the three-phase AC from the voltage detection value of the three-phase AC;
The control device for a power converter according to claim 5, further comprising: a voltage controller that generates the zero-phase current command value from a deviation between the zero-phase voltage command value and the detected value of the zero-phase voltage.

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