JP5211953B2 - Power converter - Google Patents

Description

  The present invention relates to a method for controlling a power converter that converts alternating current input into alternating current having different voltage or frequency and outputs the alternating current, and supplies a stable alternating voltage to a load.

  Patent Documents 1 to 3 show power conversion circuits that can supply power to a load without using an insulating transformer. An N-phase arm composed of a series circuit of two semiconductor switching elements in which a diode is connected in reverse parallel is connected between the positive and negative electrodes of a DC circuit of an inverse converter that performs DC-AC conversion and outputs a three-phase AC voltage. A circuit configuration in which the connection method of the AC output filter capacitor of the inverter is a star connection, and a reactor (hereinafter referred to as a neutral point output reactor) is connected between the neutral point and the series connection point of the N-phase arm. It is.

  FIG. 10 shows a circuit configuration of the three-phase four-wire non-insulated power conversion device disclosed in Patent Documents 1 to 3. In FIG. 10, 1 is a three-phase AC power source, 5 is an input filter capacitor, 6 is an input filter reactor, 2 is a forward conversion circuit that performs AC-DC conversion, 8 is a DC capacitor, 3 is an N-phase arm, and 4 is reverse conversion. Circuit 10 is an output filter reactor, 11 is an output filter capacitor, and 9 is a neutral point output reactor. The input filter capacitor 5 is also star-connected, and the neutral point of the input / output filter capacitor is connected to fix the input / output potential.

In Patent Document 1, the N-phase arm 3 is controlled so that the midpoint potential of the DC circuit of the inverse conversion circuit 4 and the potential of the series connection point (intermediate point) of the N-phase arm are equivalent, and the neutral point output A neutral point potential of the DC circuit is virtually obtained through the reactor 9.
In Patent Document 2 and Patent Document 3, in order to improve the voltage utilization factor of the DC circuit, the third harmonic signal synchronized with the sine wave signal is added to the sine wave signal that is the voltage control command signal of the inverse conversion circuit 4. And the N-phase arm 3 is controlled by a signal superimposed on the voltage control command signal of the inverse conversion circuit 4 so that the three-phase output voltage with respect to the neutral point of the output filter capacitor 11 becomes a sine wave.
JP 2000-224862 A JP 2007-274825 A JP 2000-259688 A

  In the three-phase four-wire non-insulated power converter, as shown in FIG. 11, a load 12 is provided between the neutral point of the output filter capacitor 11 and any one of the three-phase outputs (here, the W-phase). May be connected. In the case of such a configuration, the path of the current flowing in the power conversion circuit is output filter reactor 10 -inverse conversion circuit 4 -N-phase arm 3 -neutral point output reactor 9 -output filter capacitor 11, and output filter reactor 10 A voltage drop occurs in the neutral point output reactor 9.

  In such a conduction state, the voltage drop of the neutral point output reactor 9 causes the fluctuation, and in the control method of Patent Document 1, the DC circuit neutral point potential varies. The zero-phase voltage is superimposed on the three-phase output voltage with respect to the neutral point of the output filter capacitor 11 under the influence of this fluctuation. In the control methods of Patent Document 2 and Patent Document 3, the neutral point potential of the DC circuit varies depending on the sum of the superimposed signal and the voltage drop of the neutral point output reactor 9. For this reason, as in the case of Patent Document 1, the zero-phase voltage is superimposed on the three-phase output voltage with respect to the neutral point of the output filter capacitor 11.

As described above, in any of Patent Document 1, Patent Document 2, and Patent Document 3, the neutral point potential fluctuation of the DC circuit due to the voltage drop of the neutral point output reactor 9 causes neutrality of the output filter capacitor 11. The zero-phase voltage is superimposed on the three-phase output voltage for the point, and a stable sine wave voltage cannot be supplied to the load.
It is possible to add a control for detecting the neutral point potential of the DC circuit and suppressing the superposition of the zero-phase voltage to either the N-phase arm 3, the inverse conversion circuit 4 or the forward conversion circuit 2, but the voltage detector Need to be added separately.
The present invention has been made to solve the problems of the conventional control system as described above. A stable sine wave voltage is applied to the load without adding a voltage detector for detecting the neutral point potential of the DC circuit. An object of the present invention is to provide a three-phase four-wire non-insulated power converter to be supplied.

  In order to solve the above-described problem, in the first invention, a forward converter connected to a three-phase AC power source and performing AC-DC conversion by a high-frequency switching operation of a semiconductor switching element, and a DC circuit of the forward converter It consists of a series circuit of two semiconductor switching elements that are connected between DC terminals, perform DC-AC conversion by high-frequency switching operation of the semiconductor switching element, and output a three-phase AC voltage, and diodes connected in reverse parallel. An N-phase arm connected between the DC terminals of the DC circuit, and the connecting method of the filter capacitor on the forward converter AC input side and the filter capacitor on the inverse converter AC output side is a star connection, respectively. A three-phase four-wire non-insulated power conversion device in which the neutral point and the series connection point of the N-phase arm are connected via a reactor. The N-phase arm includes means for controlling a dc circuit neutral point voltage provided virtually, and the inverse converter converts a three-phase output voltage with respect to a neutral point of the filter capacitor to a normal component and a zero phase. Means for controlling the output voltage by separating into components is provided, and the output voltage of the inverse converter is controlled to a sine wave.

  In the second invention, the third harmonic signal synchronized with the output voltage command is superimposed on the control signal for each of the N-phase arm and the inverse converter, and the N-phase arm controls the voltage of the DC circuit virtual neutral point. The inverse converter separates the normal component and the zero phase component to control the output voltage.

  In a third aspect of the invention, a forward converter connected to a three-phase AC power source and performing AC-DC conversion by a high-frequency switching operation of a semiconductor switching element is connected between the DC terminals of the DC circuit of the forward converter, and the semiconductor switching It consists of a series circuit of two semiconductor switching elements connected in reverse parallel with a reverse converter that performs DC-AC conversion by high-frequency switching operation of the element and outputs a three-phase AC voltage, and is connected between the DC terminals of the DC circuit N-phase arm, and the connecting method of the filter capacitor on the forward converter AC input side and the filter capacitor on the reverse converter AC output side is a star connection, respectively, the neutral point and the N phase In a three-phase four-wire non-insulated power conversion apparatus in which a series connection point of arms is connected via a reactor, the N-phase arm has three Means for controlling the zero-phase component of the output voltage, and means for controlling the normal component of the inverse converter, respectively, and the N-phase arm and the inverse converter provide voltage control for different components of the output voltage. Do.

  In a fourth aspect of the invention, a third harmonic signal synchronized with an output voltage command is superimposed on a control signal for each of the N-phase arm and the inverter, and the N-phase arm is a voltage at a DC circuit virtual neutral point. The inverse converter separates the normal component and the zero phase component to control the output voltage.

  In the three-phase four-wire non-insulated power conversion device according to the first and second inventions of the present invention, the N-phase arm is provided with means for controlling the imaginary DC circuit neutral point voltage, and the inverse converter is a filter. Since there is a means to control the output voltage by separating the three-phase output voltage for the neutral point of the capacitor into a normal component and a zero-phase component, a voltage drop occurred in the output filter reactor and neutral point output reactor Even in this case, fluctuations in the neutral point potential of the DC circuit can be suppressed, and the three-phase output voltage with respect to the neutral point of the filter capacitor can be a sine wave.

  In the three-phase four-wire non-insulated power conversion apparatus according to the third and fourth inventions, the N-phase arm controls the zero-phase component of the three-phase output voltage, and the inverse converter controls the normal component. Since the N-phase arm and inverse converter control the voltage for different components of the output voltage, even if a voltage drop occurs in the output filter reactor or neutral point output reactor, The fluctuation of the neutral point potential can be suppressed, and the three-phase output voltage with respect to the neutral point of the filter capacitor can be a sine wave.

  The essential point of the present invention is that the N-phase arm is provided with a means for controlling the virtually-provided DC circuit neutral point voltage, and the inverse converter converts each phase voltage of the three-phase output to the neutral point of the filter capacitor with a normal component and zero. The output voltage is controlled by separating into phase components.

  FIG. 1 shows a first embodiment of the present invention. FIG. 1 shows a voltage control block diagram of each phase arm and N phase arm of the inverse conversion circuit. Each phase arm of the inverse conversion circuit performs three-phase output voltage control, and the N-phase arm controls the neutral point voltage of the DC circuit.

  FIG. 2 shows a three-phase output current necessary for control for correcting a voltage drop at the output filter reactor 10 and the neutral point output reactor 9 caused by the load current and the detection point of the three-phase output voltage to be controlled. 3 shows a three-phase four-wire non-insulated power conversion device illustrating the detection points. The voltage detector 13 detects each phase voltage based on the neutral point of the output filter capacitor 11 as a three-phase output voltage, and the current detector 14 detects a current output to the load as a three-phase output current. ing.

  As shown in the voltage control block diagram of FIG. 1, in order to control the three-phase output voltage, the zero-phase component and the components other than the zero-phase component (hereinafter referred to as normal components) are controlled separately. Further, in order to control the neutral point of the DC circuit, a three-phase output voltage and a zero-phase component of the three-phase output voltage are used. Therefore, the three-phase output voltage and the three-phase output current detected by the voltage detector and current detector of FIG. 2 are separated into a zero-phase component and a normal component.

  FIG. 3 shows a control block diagram for separating the detected three-phase output voltage and three-phase output current into a zero-phase component and a normal component. First, three-phase sums are obtained by adders 16 and 18 from the detected three-phase output voltage and three-phase output current. Next, the outputs of the adders 16 and 18 are reduced to one third by the proportional gains 36 and 37, respectively, and are set as an output voltage zero phase component Vz and an output current zero phase component Iz, respectively. The obtained zero-phase components are removed from the detected three-phase voltages and three-phase currents using the subtractors 15u, 15w, 17u, and 17w, and normal component voltages Vnu and Vnw and normal component currents Inu and Inw are removed. To extract. The normal component has a three-phase sum of zero and one of the three phases is subordinate to the other two phases, so only two phases are used for control. This time, it has two phases of U phase and W phase.

Hereinafter, the voltage control block diagram of FIG. 1 will be described in detail.
Each phase arm of the inverse conversion circuit is individually controlled, and correctors 18u and 18w including three compensators are added so that the output voltage normal component of each phase matches the output voltage command. In the corrector 18u, first, a difference between the output voltage command Vu * and the detected output voltage normal component Vnu is obtained by the subtractor 19u, and a normal voltage difference correction command is obtained by the compensator 21u. Further, in order to correct the normal voltage drop in the output filter reactor 10 due to the output current normal component Inu, a voltage drop correction command is obtained by the compensator 22u.

  Further, the sum of the voltage difference correction command and the voltage drop correction command is obtained by the adder 20u, the component outside the control band is removed by the compensator 23u, and the adder 26u is used for the output voltage command Vu * as the normal component correction command. to add. The same applies to the compensator 18w. The normal component is zero in the three-phase sum, and one of the three phases is subordinate to the other two phases. Therefore, the corrector is installed in two of the three phases and the two-phase correctors 18u and 18w. Is subtracted from the remaining one-phase command by the subtractor 27, and normal component correction for the remaining one-phase is performed.

  In addition to the above, a zero-phase component correction for controlling the zero-phase component of the output voltage is added to each phase arm of the inverse conversion circuit. The zero-phase component correction command is obtained using the corrector 18z having the same configuration as the normal component correction command. First, the difference between the output voltage zero-phase component command Vz * and the detected output voltage zero-phase component Vz is obtained by the subtractor 19z, and the zero-phase voltage difference correction command is obtained by the compensator 21z. Further, in order to correct the zero phase component voltage drop in the output filter reactor 10 due to the output current zero phase component Iz, a zero phase voltage drop correction command is obtained by the compensator 22z.

  Further, the sum of the zero-phase voltage difference correction command and the zero-phase voltage drop correction command is obtained by the adder 20z, the component outside the control band is removed by the compensator 23z, and each phase of the three phases is obtained as the zero-phase component correction command Viz *. The voltage command is added using adders 28u, 28v, 28w. Each phase is individually controlled by using the outputs of the adders 28u, 28v, 28w as voltage commands for the respective phase arms of the inverse conversion circuit. The compensators 21u, 21v, and 21w constituting the corrector 18u, the corrector 18w, and the corrector 18z are designed based on the circuit constants of the output filter reactor 10 and the output filter capacitor 11. The compensators 22u, 22v, and 22w are designed based on the circuit constants of the output filter reactor 10. The compensator 23 is designed based on the frequency of the output sine wave and the switching frequency of the inverse conversion circuit.

  The N-phase arm is controlled so that the DC circuit neutral point voltage matches the command. FIG. 4 shows an equivalent circuit for the zero phase when a load is connected between the neutral point of the output filter capacitor 11 and any one of the three-phase outputs. The load is represented as a zero-phase current source 35, the N-phase arm is represented as a voltage source 33, and the zero-phase component correction of the inverse conversion circuit is represented as a voltage source 34.

  Further, the three-phase output filter reactor 10 and the three-phase output filter capacitor 11 are replaced with a single-phase circuit. In FIG. 4, the point where the voltage source 33 and the voltage source 34 are connected is defined as a virtual neutral point Vc of the DC circuit, and the N-phase arm is controlled so that this virtual neutral point matches the command. In the control of the N-phase arm, it is assumed that the voltage source 34 corrects the voltage drop due to the zero-phase current of the output filter reactor 10z by correcting the zero-phase component of the inverse conversion circuit.

  Accordingly, it can be assumed that the equivalent circuit of FIG. 4 is configured by only the voltage source 33 of FIG. 5, and further, it can be assumed that the virtual neutral point Vc of the DC intermediate circuit is the zero-phase voltage of the three-phase output filter capacitor. The virtual neutral point can be controlled by the N-phase arm using the corrector 18n having the same configuration as the zero-phase component corrector 18z added to each phase arm of the inverse conversion circuit.

  However, the compensator 24 is designed based on the circuit constants of the neutral point output reactor 9 and the output filter capacitor 11, and the compensator 25 is designed based on the circuit constants of the neutral point output reactor 9. Further, since the output directions of the voltage source 33 and the voltage source 34 are opposite to each other, the polarity of the output of the corrector 18n is inverted by the gain 29, and the output of the gain 29 is used as the N-phase arm midpoint voltage command. Control the arm.

  FIG. 6 shows a second embodiment of the present invention. The voltage control block shown in FIG. 6 is a third harmonic signal synchronized with the sine wave signal for each phase arm voltage command and N phase arm midpoint voltage command of the inverse conversion circuit in order to improve the voltage utilization factor of the DC circuit. Adders 30u, 30v, 30w, and 30n that superimpose V3 are added to the voltage control block of FIG. This is a method for increasing the fundamental wave component of the three-phase output voltage, and the details are described in Patent Documents 2 and 3, and thus the description thereof is omitted. The control method is exactly the same as in the first embodiment.

FIG. 7 shows a third embodiment of the present invention. In the voltage control block of FIG. 7, each phase arm of the inverse conversion circuit is individually controlled so that the output voltage normal component of each phase matches the output voltage command, and the N phase arm has the zero phase component of the output voltage. Control is performed so as to match the output voltage zero-phase component command.
The configuration of the control block of each phase arm of the inverse conversion circuit is the same as that of the control block for the output voltage normal component described in the first embodiment.

  On the other hand, the configuration of the control block of the N-phase arm is the same as that of the control block for the N-phase arm described in the first embodiment. However, since the control target of the N-phase arm is the zero-phase component of the output voltage, the voltage command for the N-phase arm is not the DC circuit neutral point voltage command Vc * handled in the first embodiment, but the output voltage. The zero-phase component command Vz * is assumed.

  The compensator 31 and the compensator 32 are designed on the basis of the circuit constants of the output filter reactor 10 and the neutral point output reactor 9, and at the time of designing, the neutral point and the three-phase output of the output filter capacitor 11 are set. The equivalent circuit regarding the zero phase shown in FIG. 8 when a load is connected between any one phase is assumed. The compensator 31 is designed based on the circuit constants of the output filter reactor 10 of the zero-phase equivalent circuit, the neutral point output reactor 9 and the output filter capacitor 11, and the compensator 32 is the same as the output filter reactor of the zero-phase equivalent circuit. Design based on the circuit constants of the sex point output reactor.

FIG. 9 shows a fourth embodiment of the present invention. The voltage control block of FIG. 9 is similar to the voltage control block diagram of FIG. 7 in order to improve the voltage utilization rate of the DC circuit, and to each phase arm voltage command and N-phase arm midpoint voltage command of the inverse conversion circuit, Are added with adders 30u, 30v, 30w, and 30n that superimpose the third harmonic signal V3 synchronized with. This is a method for increasing the fundamental wave component of the three-phase output voltage, and the details are described in Patent Documents 2 and 3, and thus the description thereof is omitted. The control method is the same as in the third embodiment.
In the above embodiment, an example in which the third harmonic component is added to improve the DC voltage utilization factor is shown, but it is also possible to apply a harmonic of a multiple of 3 or a trapezoidal wave.

  The present invention can be applied to an uninterruptible power supply (UPS) or an AC power supply that requires a three-phase four-wire output.

Voltage control block diagram showing a first embodiment of the present invention Circuit diagram showing detection points of three-phase output voltage and three-phase output current of three-phase four-wire non-insulated power converter Control block diagram for separating detected three-phase output voltage and three-phase output current into normal and zero-phase components Equivalent circuit for zero phase when load is connected between neutral point of output filter capacitor and any one of three-phase outputs Equivalent circuit regarding zero phase assumed when designing compensator 24 and compensator 25 Voltage control block diagram showing a second embodiment of the present invention Voltage control block diagram showing a third embodiment of the present invention Equivalent circuit for zero phase assumed when designing compensator 31 and compensator 32 Voltage control block diagram showing a fourth embodiment of the present invention Main circuit configuration diagram of three-phase four-wire non-insulated power converter Circuit diagram when a load is connected between the neutral point of the output filter capacitor of the three-phase four-wire non-insulated power conversion circuit and any one of the three-phase outputs

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Three-phase alternating current power supply, 2 ... Forward conversion circuit, 3 ... N phase arm, 4 ... Reverse conversion circuit, 5 ... Input filter capacitor, 6 ... Input filter reactor, 7 ... Grounding point, 8 ... DC capacitor, 9 ... Neutral point output reactor,
10 ... Output filter reactor, 11 ... Output filter capacitor,
12 ... load, 13 ... voltage detector, 14 ... current detector,
15u, 15w, 17u, 17w, 19u, 19w, 19z, 19n, 27 ... subtractor,
18u, 18w, 18z, 18n ... corrector,
16, 18, 20u, 20w, 20z, 20n, 26u, 26w ... adders,
28u, 28v, 28w, 30u, 30v, 30w, 30n ... adder,
21u, 21w, 21z, 22u, 22w, 22z ... compensator,
23u, 23w, 23z, 23n, 24, 25, 31, 32 ... compensator,
33, 34 ... voltage source, 35 ... zero phase current source, 29, 36, 37 ... proportional gain

Claims (6)

A forward converter connected to a three-phase AC power source, which performs AC-DC conversion by high-frequency switching operation of the semiconductor switching element, and a DC terminal of the DC circuit of the forward converter, and DC by the high-frequency switching operation of the semiconductor switching element An inverter for performing AC conversion and outputting a three-phase AC voltage; an N-phase arm composed of a series circuit of two semiconductor switching elements connected in reverse parallel to each other and connected between DC terminals of the DC circuit; The connection method of the filter capacitor on the forward converter AC input side and the filter capacitor on the reverse converter AC output side is a star connection, and the neutral point and the series connection point of the N-phase arm are In the three-phase four-wire non-insulated power converter connected through the reactor,
The N-phase arm is provided with means for controlling a virtual circuit neutral point voltage provided virtually, and the inverse converter converts each phase voltage of the three-phase output to the neutral point of the filter capacitor into a normal component and a zero-phase component. A three-phase four-wire non-insulated power converter comprising a means for controlling the output voltage by separating the output voltage from the inverter.   The third harmonic signal synchronized with the output voltage command is superimposed on the control signal for each of the N-phase arm and the inverse converter, the N-phase arm performs voltage control of the DC circuit virtual neutral point, 2. The three-phase four-wire non-insulated power converter according to claim 1, wherein the output voltage is controlled by separating into a normal component and a zero-phase component.   The means for controlling the output voltage by separating the three-phase output voltage for the neutral point of the filter capacitor into a normal component and a zero-phase component is output by multiplying the sum of the three-phase output voltages by 1/3. The three-phase four-wire non-insulated device according to claim 1 or 2, wherein the output voltage is controlled by using a voltage zero-phase component and subtracting the zero-phase component from a three-phase output voltage as an output voltage normal component. Type power converter. A forward converter connected to a three-phase AC power source, which performs AC-DC conversion by high-frequency switching operation of the semiconductor switching element, and a DC terminal of the DC circuit of the forward converter, and DC by the high-frequency switching operation of the semiconductor switching element An inverter for performing AC conversion and outputting a three-phase AC voltage; an N-phase arm composed of a series circuit of two semiconductor switching elements connected in reverse parallel to each other and connected between DC terminals of the DC circuit; The connection method of the filter capacitor on the forward converter AC input side and the filter capacitor on the reverse converter AC output side is a star connection, and the neutral point and the series connection point of the N-phase arm are In the three-phase four-wire non-insulated power converter connected through the reactor,
The N-phase arm includes means for controlling a zero-phase component of a three-phase output voltage, and the inverse converter includes means for controlling a normal component. A three-phase four-wire non-insulated power converter characterized by performing voltage control on different components.   A third harmonic signal synchronized with an output voltage command is superimposed on a control signal for each of the N-phase arm and the inverse converter, the N-phase arm performs voltage control of a DC circuit virtual neutral point, and the inverse conversion 4. The three-phase four-wire non-insulated power conversion device according to claim 3, wherein the power source is controlled by separating it into a normal component and a zero-phase component.   The means for controlling the output voltage by separating the normal component and the zero-phase component is obtained by multiplying the sum of the three-phase output voltages by 1/3 as the output voltage zero-phase component, and from the three-phase output voltage to the zero-phase 6. The three-phase four-wire non-insulated power converter according to claim 5, wherein the output voltage is controlled by subtracting the component as an output voltage normal component.

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