JP2009153297A - Controller of self-excited converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of a self-excited converter that suppresses a zero-phase component of an output current of a converter by the minimum addition of a control circuit while keeping characteristics equivalent to the conventional orthogonal axis control with regard to current control to a system, in the self-excited converter connected to a three-phase AC circuit using single-phase converters for three phases. <P>SOLUTION: The controller of the self-excited converter structures three phases using three single-phase converters and systematically connects to a three-phase AC system via a transformer whose AC system side windings are delta-connected. The controller includes a current detection section, which detects a three-phase current inside the delta connection; an adder 16, which calculates the sum of three-phase currents detected by the current detection section; a control section, which outputs an AC output voltage command value to the self-excited converter based on the three-phase current detected by the current detection section; and adders 19a, 19b, 19c, which are correction sections that perform common corrections to each phase for the AC output voltage command value output by the control section according to the sum of three-phase currents calculated by the adder 16. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for a self-excited converter used in a DC power transmission / DC interconnection system, a power supply system, or a reactive power compensator in a power system.

  A typical power system of a power company is a three-phase AC circuit. The self-excited converter installed in the three-phase AC circuit is composed of three single-phase converters or three-phase converters, and is connected to the power system via the three-phase transformer.

 FIG. 7A is a diagram illustrating a main circuit configuration of a general self-excited converter system connected to a three-phase AC system using three single-phase converters. FIG. 7B is a diagram showing an example of a control block of a general self-excited converter system connected to a three-phase AC system using three single-phase converters.

 The three single-phase converters 1a, 1b, and 1c constitute a three-phase self-excited converter, and are connected to the AC bus 3 via the converter transformer 2. AC bus 3 is connected to a three-phase power system. The three single-phase converters 1a, 1b, and 1c are each composed of four arms each composed of an anti-parallel circuit of a self-extinguishing semiconductor element and a diode, and the DC side of each single-phase converter is a DC terminal P and a DC terminal. N is commonly connected. Further, the DC sides of the three single-phase converters 1a, 1b, and 1c are kept at a constant DC voltage by a DC power source or a DC capacitor (not shown) connected between the DC terminals PN.

 On the other hand, the three single-phase converters 1a, 1b, and 1c output an alternating voltage having an arbitrary magnitude and phase to the alternating current side by controlling the switching of the self-extinguishing semiconductor element. The converter output currents Ia, Ib, and Ic flow based on the voltage difference and phase difference between the converter output voltage and the AC bus 3.

When the system side winding of the converter transformer 2 is Δ-connected as shown in FIG. 7A, the currents Irs, Ist, Itr in the Δ winding are the converter output currents Ia, Ib, Ic and Is equivalent. On the other hand, the expression (1) is a current between the current flowing out to the AC system (current flowing at the connection point between the transformer for transformer 2 and the AC bus 3) Ir, Is, It and the Δ winding current Irs, Ist, Itr. The relationship is shown.

  Here, when the currents Irs, Ist, Itr are three-phase balanced, the currents Ir, Is, It are √3 times the currents Irs, Ist, Itr, respectively, and are 30 ° delayed currents. It is.

  On the other hand, when a circulating current flows in the Δ winding, that is, when the currents Irs, Ist, and Itr include a zero-phase component, the currents Ir, Is, and It flowing out to the AC system are (1 As is clear from the equation (1), since it does not include the zero-phase component, it is not necessarily √3 times.

 Next, control of a general self-excited converter will be described. The self-excited converter can independently control the active power and the reactive power on the AC output side, and in the case of a converter connected to a three-phase AC circuit, as a means for that, generally an orthogonal axis (dq axis) ) Use current control. As shown in FIG. 7A, the AC voltage detectors 4a, 4b, 4c detect the AC bus voltages Vr, Vs, Vt. The AC current detectors 5a, 5b, and 5c detect the outflow currents Ir, Is, and It to the AC system.

 As shown in FIG. 7B, the detected AC bus voltages Vr, Vs, Vt are input to the phase detection circuit 6 of the converter control system. Similarly, the currents Ir, Is, It are input to the three-phase / two-phase conversion circuit 7.

The three-phase / two-phase conversion circuit 7 converts the three-phase currents Ir, Is, It into two-phase currents Iα, Iβ that are 90 ° out of phase using the equation (2).

  On the other hand, the phase detection circuit 6 detects the R phase voltage, that is, the voltage phase θ of the AC bus 3 with reference to Vr, and the orthogonal dq-axis voltages Vd and Vq. The dq-axis voltages Vd and Vq are voltage values of the AC bus 3 on the rotating coordinate system with the voltage phase θ as a reference, and are normally DC amounts.

The two-phase currents Iα and Iβ output from the three-phase / two-phase conversion circuit 7 and the voltage phase θ output from the phase detection circuit 6 are input to the coordinate conversion circuit 8. The coordinate conversion circuit 8 converts the output current into dq axis amounts of the active power component Id and the reactive power component Iq using the equation (3). Here, Id and Iq are current values on the rotating coordinate system with the phase θ as a reference, like Vd and Vq, and are normally DC amounts.

 Id and Iq are matched with the active current command value Idref and the reactive current command value Iqref given from the host control system, and the difference between them is input to the AC current control circuit 9. The alternating current control circuit 9 outputs a signal such that the inputted difference becomes zero to the adders 10a and 10b.

 The adders 10a and 10b add the dq-axis voltages Vd and Vq of the AC bus 3 output from the phase detection circuit 6 and the output from the AC current control circuit 9 and add the converter output voltage signals Vdc and Vqc to the two-phase / Output to the three-phase conversion circuit 11. The converter output voltage signals Vdc and Vqc are dq axis amounts of the converter output voltage with the voltage phase θ of the AC bus 3 as a reference phase. That is, the dq-axis voltages Vd and Vq are the AC system side voltages of the converter transformer 2, while the converter output voltage signals Vdc and Vqc are the converter side voltages of the converter transformer 2 and have the same rotation. This is the dq axis amount viewed from the coordinate system.

The two-phase / three-phase conversion circuit 11 calculates the converter AC output voltage signals Vac, Vbc, and Vcc using the equation (4) and outputs them to the pulse generation circuit 12. The converter output voltage signals Vdc and Vqc are steadily DC, whereas the converter AC output voltage signals Vac, Vbc and Vcc are three-phase sine wave signals.

 The pulse generation circuit 12 uses, for example, means such as PWM (Pulse Width Modulation) control so that the AC output voltage of the self-excited converter (the converter side voltage of the converter transformer 2 in FIG. 7A) is Vac and Vbc, respectively. , Vcc, on / off pulses are output to the semiconductor elements of the single-phase converters 1a, 1b, 1c.

 By the control shown in FIG. 7B described above, the self-excited converter composed of the single-phase converters 1a, 1b, and 1c has effective power components and reactive power components of the currents Ir, Is, and It supplied to the system. The operation is performed so as to be equal to the current command value Idref and the reactive current command value Iqref.

  Patent Document 1 discloses a three-phase voltage converter in a three-phase power converter in which the alternating current sides of a plurality of single-phase inverters are connected in series, and the output voltage of each phase is controlled in gradation by a combination of the selected single-phase inverters. A power converter that reduces electromagnetic noise by suppressing current flowing from a neutral point by preventing unbalance is described.

  In this power converter, a single-phase multiple converter is configured by connecting a plurality of AC sides of a single-phase inverter that converts DC power from a DC power source into AC power in series, and the single-phase multiple conversion is connected in three phases. Powers a three-phase load. The single-phase multiple converter for each phase performs gradation control of the output voltage of each phase based on the sum of the generated voltages based on a predetermined combination selected from a plurality of single-phase inverters. Means for detecting the output voltages of the first and second single-phase multiple converters, and the detected two output voltages are added, and the added value is inverted between positive and negative. And a third single-phase multiple converter that performs gradation control so that the output voltage becomes the calculated voltage value.

  According to this power conversion device, a power converter that promotes cost reduction, downsizing, and simplification can be obtained, and the three-phase voltage can be controlled to be balanced and electromagnetic noise can be reduced. Adjustment control can be realized.

  Patent Document 2 describes a power converter that can suppress zero-phase noise current by zero-phase cancellation control to reduce electromagnetic noise, and can effectively suppress the occurrence of current distortion in a low-frequency region.

  This power conversion device has a control device that controls the output voltage of each phase by the sum of the voltage of each phase of the three-phase three-level inverter and each generated voltage by the combination of a plurality of single-phase inverters. This controller converts the three-phase AC voltage command into a two-phase AC voltage command vector, and selects three spatial voltage vectors for two-phase AC that have three-phase voltage totals close to this two-phase AC voltage command vector. Then, the two-phase AC voltage command vector is expressed as a time average according to the distances from these three spatial voltage vectors, and a voltage that makes the current waveform sinusoidal while outputting the zero-phase voltage to zero is output.

According to this power converter, both electromagnetic noise current and current distortion can be suppressed. Furthermore, since a three-phase three-level inverter that outputs a three-phase voltage from a DC power supply is used, the number of units of the single-phase inverter can be reduced as a whole, and the configuration can be simplified.
JP 2004-120968 A JP 2007-37355 A

 As shown in FIG. 7A, in the case where the self-excited converter connected to the three-phase AC system uses three single-phase converters and the AC system side of the converter transformer 2 has a Δ winding configuration. The currents Ir, Is, It flowing in the AC system do not include a zero phase component, but the currents Irs, Ist, Itr in the Δ winding include a zero phase component, and the zero phase component circulates in the Δ winding. There may be.

 In this case, the Δ winding internal currents Irs, Ist, Itr are equivalent to the output currents Ia, Ib, Ic of the single-phase converters 1a, 1b, 1c, respectively. That is, the output currents of the single-phase converters 1a, 1b, and 1c include a zero-phase component. As shown in FIG. 7A, when the current detectors 5a, 5b, and 5c are installed outside the transformer Δ winding, the zero-phase current cannot be detected. The control device for the self-excited converter shown in FIG. 1 cannot be suppressed by control even when a zero-phase current is generated. Therefore, the Δ winding internal currents Irs, Ist, Itr and the converter output currents Ia, Ib, Ic increase, which may cause an increase in power loss and an overcurrent of the converter.

 8A and 8B are diagrams showing a main circuit configuration in the case of detecting a zero-phase current in a general self-excited converter system connected to a three-phase AC system using three single-phase converters. It is.

 In order to detect the current including the zero-phase current, as shown in FIGS. 8A and 8B, the current detectors 5a, 5b, and 5c are provided inside the transformer Δ winding or on the converter side winding. Need to be installed in series. However, in this case, even if the three-phase / two-phase conversion circuit 7 performs current control on the dq axis by converting the detected current to the three-phase / two-phase using the equation (2), the self-excited converter For the reason described below, the control device does not reflect the zero-phase component in the control, and when the zero-phase current is generated, the control device cannot suppress the zero-phase current by the control.

The three-phase converter outputs Ia (= Irs), Ib (= Ist), and Ic (= Itr) can be expressed as follows when the positive-phase component I1 and the zero-phase component I0 are included.

When the three-phase / two-phase conversion circuit 7 converts the currents Ia, Ib, and Ic shown in the equations (7), (8), and (9) into the two-phase signals using the equation (2), the two-phase signals are as follows: It is expressed in

  As apparent from the equations (10) and (11), the three-phase / two-phase conversion is performed by the three-phase / two-phase conversion circuit 7 even if the zero-phase component I0 is included in the converter output current detection value. The zero-phase component is canceled when Therefore, the control device having the main circuit configuration of the self-excited converter as shown in FIG. 8 does not reflect the zero phase component in the control, and the converter output currents Ia, Ib, Ic include the zero phase component. However, the zero phase component cannot be suppressed. As a result, the Δ winding internal currents Irs, Ist, Itr and the converter output currents Ia, Ib, Ic are increased, causing a problem of increasing power loss and overcurrent of the converter.

  FIG. 9 is a general control block diagram in the case of suppressing zero-phase current in a self-excited converter system using three single-phase converters. As a conventional means for solving the above-described problem, the control device shown in FIG. 9 includes a current control circuit (sine wave alternating current control circuits 14a, 14b, 14c) for each phase. The sine wave alternating current control circuits 14a, 14b, and 14c are provided with three units of control used in the single-phase converter individually. The control for the self-excited converter performed by the configuration of FIG. 9 uses the detected sine wave current as it is, unlike the method of converting the current into two orthogonal axes as in the control shown in FIG. 7B.

  In FIG. 9, the phase detection circuit 6 detects the voltage phase θ of the AC bus 3 with reference to the RS phase line voltage, that is, Vrs, based on the line voltage detection values Vrs, Vst, Vtr, and a current command value calculation circuit. 13 is output. The line voltage detection values Vrs, Vst, and Vtr may be detected by providing a voltmeter that detects the voltage value between the lines, but the AC buses detected by the AC voltage detectors 4a, 4b, and 4c. You may obtain | require by the difference of voltage Vr, Vs, Vt.

Based on the active current command value Idref, the reactive current command value Iqref, and the voltage phase θ given from the upper control system, the current command value calculation circuit 13 calculates the current command values Iaref, Ibref, and Icref of each phase by the following equations. Use to calculate.

  That is, in the steady state, the effective current command value Idref and the reactive current command value Iqref are DC amounts, but the current command values Iaref, Ibref, and Icref for each phase are sinusoidal signals that are 120 ° out of phase.

  The subtractors 21a, 21b, and 21c include current command values Iaref, Ibref, and Icref, and Δ winding internal currents Irs, Ist, Itr, or converter side winding current detection values Ia, Ib, and Ic of the converter transformer 2. And the difference between the two is output to the sine wave alternating current control circuits 14a, 14b and 14c.

  Each of the sine wave AC current control circuits 14a, 14b, 14c is constituted by, for example, a proportional integration circuit or a first-order lag circuit, and the difference between the current command values Iaref, Ibref, Icref and the current detection value is zero. Output a signal.

  The adders 15a, 15b, and 15c add the output signals output from the sine wave AC current control circuits 14a, 14b, and 14c and the line voltage detection values Vrs, Vst, and Vtr of the AC bus 3, and the result is obtained. The converter output voltages Vac, Vbc, and Vcc, which are obtained values, are output to the pulse generation circuit 12. The converter output voltages Vac, Vbc, Vcc are voltages necessary for outputting the effective current Idref and the reactive current Iqref.

  By using this method, the current of each single-phase converter (1a, 1b, 1c) is individually controlled, so that the Δ winding internal currents Irs, Ist, Itr and the converter output currents Ia, Ib, Ic are zero. There is no problem of increasing the transformer winding loss or causing the converter overcurrent due to the large phase component.

  However, since three current control circuits (14a, 14b, 14c) are required, the circuit of the control device is complicated as a whole. In addition, since the control device shown in FIG. 9 performs control using a sine wave, it is difficult to remove harmonics compared to the case where control is performed using a DC amount (dq axis amount) like the control device shown in FIG. Furthermore, there is a problem that the response speed is slow and a problem that an unbalance due to a reverse phase component is likely to occur because the three phases are individually controlled. Therefore, the control device shown in FIG. 9 has an effect of suppressing the increase in transformer winding loss and the overcurrent of the converter, but the response characteristics of the currents Ir, Is, It flowing to the system are dq axis control. Bad compared to doing.

  Moreover, although the power converter device described in patent document 1 and patent document 2 has proposed all about the control method which suppresses the zero phase output of the converter which used three single phase converters, This is a proposal specialized for multiple-connected systems, and procedures such as using space vectors are complicated.

  Therefore, the present invention is a self-excited converter connected to a three-phase AC circuit using three phases of single-phase converters, while maintaining the same characteristics as the conventional orthogonal axis control for the control of the current flowing to the system, It is an object of the present invention to provide a control device for a self-excited converter that can suppress the zero-phase component of the converter output current by adding a minimum control circuit.

  In order to solve the above problems, the control device for a self-excited converter according to the present invention comprises three phases using three single-phase converters, and the AC system side winding is Δ A control device for a self-excited converter linked to a three-phase AC system via a connected transformer, a current detection unit for detecting a three-phase current inside a Δ connection, and detected by the current detection unit An adder that calculates the sum of three-phase currents, a controller that outputs an AC output voltage command value for the self-excited converter based on the three-phase current detected by the current detector, and a calculator that is calculated by the adder And a correction unit that performs correction common to each phase on the AC output voltage command value output by the control unit in accordance with the sum of three-phase currents.

  The second aspect of the present invention is a self-excited converter in which three single-phase converters are used to form a three-phase converter and the AC system side winding is linked to the three-phase AC system via a transformer having a Δ connection. A control device that detects a three-phase current output from the three single-phase converters; an adder that calculates a sum of three-phase currents detected by the current detector; and the current A control unit that outputs an AC output voltage command value for the self-excited converter based on the three-phase current detected by the detection unit, and an output from the control unit according to the sum of the three-phase currents calculated by the addition unit. And a correction unit that performs correction common to each phase on the AC output voltage command value.

  A third aspect of the invention is a self-excited converter in which three single-phase converters are used to form a three-phase, and the AC system side winding is linked to the three-phase AC system via a transformer having a Δ connection. A control device, a first current detector that detects a three-phase current inside the Δ connection, and a second current that detects a three-phase current that is a line current flowing from the Δ connection to the three-phase AC system. AC output voltage for the self-excited converter based on the three-phase current detected by the detection unit, the addition unit for calculating the sum of the three-phase currents detected by the first current detection unit, and the second current detection unit A control unit that outputs a command value, and a correction unit that performs correction common to each phase on the AC output voltage command value output by the control unit in accordance with the sum of the three-phase currents calculated by the addition unit. It is characterized by providing.

  A fourth aspect of the invention is a self-excited converter in which three single-phase converters are used to form a three-phase converter and the AC system side winding is linked to the three-phase AC system via a transformer having a Δ connection. A control device, a first current detection unit that detects a three-phase current output by the three single-phase converters, and a three-phase current that is a line current that flows from the Δ connection to the three-phase AC system A self-excited type based on the three-phase current detected by the second current detection unit, the addition unit for calculating the sum of the three-phase currents detected by the first current detection unit, and the three-phase current detected by the second current detection unit A control unit that outputs an AC output voltage command value for the converter, and a correction common to each phase with respect to the AC output voltage command value output by the control unit according to the sum of the three-phase currents calculated by the adding unit And a correction unit for performing the above.

  According to the control device for the self-excited converter according to the present invention, the Δ winding current and the converter output current of the transformer for the converter are maintained while maintaining the response characteristics of the orthogonal axis (dq axis) control conventionally used. It is possible to suppress the superimposition of the zero phase component, and to prevent an increase in power loss and occurrence of converter overcurrent.

  Embodiments of a control device for a self-excited converter according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a control block diagram of a control device for a self-excited converter according to Embodiment 1 of the present invention. The difference from the control block shown in FIG. 7B is that an adder 16, a proportional circuit 17 having a gain of 1/3, a proportional integration circuit 18, and adders 19a, 19b, and 19c are newly added. .

  Further, the main circuit configuration of the self-excited converter controlled by the control device is the same as the main circuit configuration shown in FIG. That is, this self-excited converter constitutes a three-phase using three single-phase converters 1a, 1b, and 1c, and a three-phase through a transformer for transformer 2 in which an AC system side winding is Δ-connected. It is linked to an AC system and controlled by the control device of the present invention. Here, the converter transformer 2 corresponds to the transformer of the present invention.

  The current detectors 5a, 5b, and 5c correspond to the current detection unit of the present invention, detect the three-phase current (Δ winding currents Irs, Ist, Itr) inside the Δ connection, and the three-phase / two-phase conversion circuit 7 And output to the adder 16.

  The adder 16 corresponds to the adding unit of the present invention, and calculates the sum of the three-phase currents detected by the current detectors 5a, 5b, and 5c. That is, the adder 16 adds the Δ winding currents Irs, Ist, Itr for three phases, and outputs the added value to the proportional circuit 17.

  The proportional circuit 17 has a gain of 1/3, and outputs to the proportional integration circuit 18 a signal that is 1/3 of the sum of the three-phase currents output from the adder 16. The signal output from the proportional circuit 17 corresponds to the zero-phase current I0.

  The proportional integration circuit 18 performs a proportional integration process on the signal output from the proportional circuit 17. The proportional circuit 17 is not necessarily an essential configuration for the control device of the present invention. Since the proportional integration circuit 18 amplifies the input signal based on its own amplification factor (gain), the proportional integration circuit 18 sets the value including the gain 1/3 of the proportional circuit 17 as the amplification factor. This is because it has a function equivalent to that of the circuit 17 and an equivalent effect can be obtained.

  Therefore, it can be said that the proportional integration circuit 18 performs a proportional integration process on the sum of the three-phase currents calculated by the adder 16.

  The phase detection circuit 6, the three-phase / two-phase conversion circuit 7, the coordinate conversion circuit 8, the alternating current control circuit 9, the adders 10a and 10b, and the two-phase / three-phase conversion circuit 11 are illustrated in FIG. This is the same as the conventional control device shown, and redundant description is omitted. The phase detection circuit 6, the three-phase / two-phase conversion circuit 7, the coordinate conversion circuit 8, the alternating current control circuit 9, the adders 10a and 10b, and the two-phase / three-phase conversion circuit 11 are entirely included in the present invention. And outputs an AC output voltage command value for the self-excited converter based on the three-phase current detected by the current detectors 5a, 5b, and 5c.

  Here, the two-phase / three-phase conversion circuit 11 calculates and adds the converter AC output voltage signals Vac ′, Vbc ′, Vcc ′ corresponding to the AC output voltage command value of the present invention using the equation (4). To the devices 19a, 19b, 19c.

  The adders 19a, 19b, and 19c correspond to the correction unit of the present invention, and are common to each phase for the AC output voltage command value output by the control unit according to the sum of the three-phase currents calculated by the adder 16. Perform the correction.

  Specifically, the adders 19a, 19b, and 19c are controlled by the control unit based on the correction value calculated by the proportional integration circuit 18 performing the proportional integration process on the sum of the three-phase currents calculated by the adder 16. Correction common to each phase is performed on the output AC output voltage command value.

  That is, the adders 19a, 19b, and 19c subtract the correction value output from the proportional integration circuit 18 from the AC output voltage command values Vac ′, Vbc ′, and Vcc ′ output from the two-phase / three-phase conversion circuit 11. The final converter output voltage signals Vac, Vbc, Vcc are obtained and output to the pulse generation circuit 12. In other words, the adders 19a, 19b, and 19c are the proportional-integral circuit 18 that is given by the negative sign and the AC output voltage command values Vac ′, Vbc ′, and Vcc ′ output by the two-phase / three-phase conversion circuit 11. Is added to the correction value obtained by, and output.

  Other configurations are the same as those of the conventional configuration described above with reference to FIGS. 7B and 8A, and redundant description is omitted.

  Next, the operation of the control device for the self-excited converter according to the present embodiment configured as described above will be described. The main circuit configuration of the self-excited converter in this embodiment is the same as that shown in FIG. 8A as described above, and the operation of the self-excited converter is also the same.

  First, the case where the current circulating through the Δ winding connected to the AC system side of the converter transformer 2 is zero, that is, the case where the zero-phase current I0 is not generated will be described. In this case, the currents Irs, Ist, Itr inside the Δ winding do not include a zero-phase component.

  Therefore, the adder 16 calculates the sum of the three-phase currents detected by the current detectors 5a, 5b, and 5c, but the value obtained by adding the three-phase Δ winding currents Irs, Ist, and Itr is zero. Therefore, zero is output to the proportional circuit 17.

  Since the input value is zero, the proportional circuit 17 outputs zero to the proportional integration circuit 18. Similarly, since the signal output from the proportional circuit 17 is zero, the proportional integration circuit 18 is zero even if the proportional integration processing is performed, and outputs zero to the adders 19a, 19b, and 19c.

  The phase detection circuit 6, the three-phase / two-phase conversion circuit 7, the coordinate conversion circuit 8, the alternating current control circuit 9, the adders 10a and 10b, and the two-phase / three-phase conversion circuit 11 corresponding to the control unit of the present invention as a whole. Outputs an AC output voltage command value for the self-excited converter based on the three-phase current detected by the current detectors 5a, 5b, 5c, as in the conventional control device described with reference to FIG.

  Therefore, the 2-phase / 3-phase conversion circuit 11 calculates the converter AC output voltage signals Vac ′, Vbc ′, Vcc ′ corresponding to the AC output voltage command value of the present invention using the equation (4), and adds the adder. It outputs to 19a, 19b, 19c.

  Since the values output from the proportional integration circuit 18 are zero, the adders 19a, 19b, and 19c do not correct the AC output voltage command value output from the control unit, and output it directly to the pulse generation circuit 12. To do.

  Therefore, when the zero-phase current I0 is not generated, the control device of the present embodiment performs current control using the orthogonal axis (dq axis) equivalent to the conventional control device shown in FIG. 7B.

  Next, a case where a current circulating in the Δ winding connected to the AC system side of the transformer for transformer 2 is generated, that is, a case where a zero-phase current I0 is generated will be described. In this case, the currents Irs, Ist, Itr in the Δ winding include a zero-phase component.

  The zero-phase current I0 circulating inside the Δ winding has a common magnitude and direction (positive / negative) in three phases. Therefore, the adder 16 is proportional to the sum of the three-phase currents detected by the current detectors 5a, 5b, and 5c, that is, 3 × I0 that is a value obtained by adding the Δ winding currents Irs, Ist, and Itr for the three phases. Output to the circuit 17.

  Since the proportional circuit 17 has a gain of 1/3, the zero-phase current I0 is output to the proportional integration circuit 18. The proportional integration circuit 18 performs proportional integration processing on the zero-phase current I0, which is a signal output from the proportional circuit 17, and outputs signals corresponding to the magnitude and direction (positive / negative) of the zero-phase current I0 to the adders 19a and 19b. , 19c.

  On the other hand, the phase detection circuit 6, the three-phase / two-phase conversion circuit 7, the coordinate conversion circuit 8, the alternating current control circuit 9, the adders 10a and 10b, and the two-phase / three-phase conversion corresponding to the control unit of the present invention as a whole. The circuit 11 outputs an AC output voltage command value for the self-excited converter based on the three-phase current detected by the current detectors 5a, 5b, and 5c, similarly to the conventional control device described with reference to FIG. .

  Therefore, the 2-phase / 3-phase conversion circuit 11 calculates the converter AC output voltage signals Vac ′, Vbc ′, Vcc ′ corresponding to the AC output voltage command value of the present invention using the equation (4), and adds the adder. It outputs to 19a, 19b, 19c.

  The adders 19a, 19b, and 19c subtract the correction value calculated by performing the proportional integration process by the proportional integration circuit 18 from the AC output voltage command values Vac ', Vbc', and Vcc 'to obtain the AC output voltage command value. On the other hand, correction common to each phase is performed, and corrected AC output voltage command values Vac, Vbc, Vcc are output to the pulse generation circuit 12. That is, the adders 19a, 19b, and 19c correct the AC output voltage command value so that the zero-phase current I0 approaches zero. Since the zero-phase current is common to the three phases, the same amount of correction is performed for each of the three-phase voltages.

  As described above, according to the control device for the self-excited converter according to the first embodiment of the present invention, the proportional integration circuit 18, the proportional circuit 17, the adder 16 are added to the conventional dq axis control circuit (the control unit in the present invention). By adding only the adders 19a, 19b, and 19c, while maintaining a high-speed response characteristic with high independence between active power and reactive power by dq axis control, the Δ winding in the transformer transformer 2 The zero-phase component of the circulating current and the converter output current can be suppressed. Therefore, while maintaining the response characteristics of the conventionally used orthogonal axis (dq axis) control, it is possible to suppress the zero-phase component from being superimposed on the Δ winding current and the converter output current of the transformer 2 for the converter. Increase in loss and occurrence of converter overcurrent can be prevented.

  Further, since the proportional integration circuit 18 is provided, an appropriate PI control is performed on the AC output voltage command value in order to suppress the zero-phase component.

  FIG. 2 is a diagram illustrating comparison of output current waveforms of the self-excited converter according to whether or not the control device for the self-excited converter according to the present embodiment is applied. FIG. 2A shows an output current waveform of the self-excited converter when the conventional self-excited converter control device is applied. FIG. 7A shows the self-excited converter having the main circuit configuration shown in FIG. It is a figure at the time of applying the conventional dq axis control shown to (b). FIG. 2B shows an output current waveform of the self-excited converter when the self-excited converter control device of the present invention is applied, and the self-excited converter having the main circuit configuration shown in FIG. It is a figure at the time of applying the control apparatus shown in FIG.

  The waveforms of the currents Ir, Is, It flowing out to the AC system and the dq axis currents Id, Iq used in the control are almost the same in any case. However, in the case of FIG. 2A, the Δ winding currents Irs, Ist, Itr are greatly different from the sine wave due to the superposition of a large zero-phase current, and the magnitude of the current is also √3 of the system outflow current. Much larger than double. On the other hand, the Δ winding currents Irs, Ist, Itr shown in FIG. 2B are equivalent to the system outflow current, and the magnitude of the current is √3 times the system outflow current.

  As described above, by applying the control device shown in FIG. 1, a self-excited converter connected to a three-phase power circuit using three single-phase converters is used for dq axis control conventionally used. While maintaining the response characteristics, it is possible to prevent the zero-phase component from being superimposed on the Δ winding current and the converter output current of the transformer 2 for the converter, thereby preventing an increase in power loss and the occurrence of a converter overcurrent. it can.

  FIG. 3 is a control block diagram of the control device for the self-excited converter according to the second embodiment of the present invention. The difference from the control device shown in FIG. 1 described above is that a filter circuit 20 is newly added.

  Further, the main circuit configuration of the self-excited converter controlled by the control device is the same as the main circuit configuration shown in FIG. That is, this self-excited converter constitutes a three-phase using three single-phase converters 1a, 1b, and 1c, and a three-phase through a transformer for transformer 2 in which an AC system side winding is Δ-connected. It is linked to an AC system and controlled by the control device of the present invention.

  The filter circuit 20 performs a filtering process on the zero-phase current I0 output from the proportional circuit 17 and outputs the filtered signal to the proportional integration circuit 18. The filter circuit 20 removes harmonic components using, for example, a first-order lag circuit or a band rejection filter.

  Therefore, the adders 19a, 19b, and 19c are based on correction values calculated by subjecting the sum of the three-phase currents calculated by the adder 16 to filter processing by the filter circuit 20 and proportional integration processing by the proportional integration circuit 18. The common correction for each phase is performed on the AC output voltage command value output by the control unit.

  Note that the proportional circuit 17 is not necessarily an essential configuration for the control device of the present invention, as in the first embodiment, and can be omitted. Since the proportional integration circuit 18 and the filter circuit 20 amplify the input signal based on their own amplification factor (gain), the value including the gain 1/3 of the proportional circuit 17 is used as the amplification factor for the proportional integration circuit 18 or the filter. This is because setting to the circuit 20 has a function equivalent to that of the proportional circuit 17 and an equivalent effect can be obtained.

  Other configurations are the same as those of the first embodiment, and redundant description is omitted.

  Next, the operation of the control device for the self-excited converter according to the present embodiment configured as described above will be described. The main circuit configuration of the self-excited converter in the present embodiment is the same as that shown in FIG. 8A as described above, and the operation of the self-excited converter is the same as that of the first embodiment.

  The output current of the self-excited converter is theoretically superimposed with harmonic components of various orders depending on the frequency of PWM (Pulse Width Modulation) to be used. Particularly, harmonics of orders of multiples of 3 are almost zero-phase components when the three phases are operating in equilibrium, and the zero-phase current contains many harmonic components.

  One of the purposes of using the converter transformer 2 having the AC system side winding as the Δ connection is to prevent the above-described zero-phase harmonic component from flowing out to the system side. As described above, since the zero-phase current includes many harmonic components, when the zero-phase current is detected and used for feedback control as in the present invention, the adders 19a, 19b, and 19c serving as correction units are controlled. There is a possibility that the vibration of the signal is increased and the harmonic component of the output current is increased or the control is unstable. However, since the control device for the self-excited converter according to the present embodiment includes the filter circuit 20, the harmonic component of the zero-phase current can be reduced.

  Therefore, the filter circuit 20 performs a filtering process on the zero-phase current I 0 that is a signal output from the proportional circuit 17 to reduce the harmonic component, and outputs the reduced harmonic component to the proportional integration circuit 18.

  Other operations are the same as those in the first embodiment, and redundant description is omitted.

  As described above, according to the control device for a self-excited converter according to the second embodiment of the present invention, in addition to the effects of the first embodiment, the harmonic component of the zero-phase current detection value is reduced, and the output current harmonic is reduced. The zero-phase current suppressing effect equivalent to that of the control device according to the first embodiment can be obtained while preventing the increase in control and instability of control.

  In the first embodiment and the second embodiment, the main circuit configuration of the self-excited converter is the same as the main circuit configuration shown in FIG. 8A described above, and therefore the control device uses the current detector in FIG. Control was performed using the three-phase current (Δ winding currents Irs, Ist, Itr) inside the Δ connection detected by 5a, 5b, 5c. However, even if the output currents Ia, Ib, and Ic of the single-phase converters 1a, 1b, and 1c are used, the control device can perform the same control.

  1 is a control block diagram of a control device for a self-excited converter according to a third embodiment of the present invention, which is the same as that of the first embodiment. However, the current input to the three-phase / two-phase conversion circuit 7 is not the Δ winding currents Irs, Ist, Itr but the converter output currents Ia, Ib, Ic.

  The main circuit configuration of the self-excited converter controlled by the control device is the same as the main circuit configuration shown in FIG. As shown in FIG. 8B, the current detectors 5a, 5b, and 5c are installed at connection points between the three single-phase converters 1a, 1b, and 1c and the converter transformer 2.

  Current detectors 5a, 5b, and 5c shown in FIG. 8 (b) correspond to the current detection unit of the present invention, and the three-phase currents (converter output currents) output by the three single-phase converters 1a, 1b, and 1c. Ia, Ib, Ic) are detected and output to the three-phase / two-phase conversion circuit 7 and the adder 16.

  As apparent from the comparison between FIG. 8A and FIG. 8B, the Δ winding currents Irs, Ist, Itr and the converter output currents Ia, Ib, Ic are all of the converter transformer 2. If the winding ratio is n: 1, the amperage values are Irs = n × Ia, Ist = n × Ib, Itr = n × Ic. These current values are normalized according to the voltage, that is, the turns ratio, so that Irs (pu) = Ia (pu), Ist (pu) = Ib (pu), Itr (pu) = Ic (pu) Get a relationship. Therefore, the control device of the present invention can perform the same control regardless of which current is used.

  The adder 16 corresponds to the adding unit of the present invention, and calculates the sum of the three-phase currents detected by the current detectors 5a, 5b, and 5c. That is, the adder 16 adds the three-phase converter output currents Ia, Ib, and Ic, and outputs the added value to the proportional circuit 17.

  The proportional circuit 17 and the proportional integration circuit 18 are the same as those in the first embodiment, and redundant description is omitted.

  The phase detection circuit 6, the 3-phase / 2-phase conversion circuit 7, the coordinate conversion circuit 8, the alternating current control circuit 9, the adders 10a and 10b, and the 2-phase / 3-phase conversion circuit 11 are the same as those in the first embodiment. The whole corresponds to the control unit of the present invention.

  Other configurations are the same as those of the first embodiment described above, and a duplicate description is omitted. As in the second embodiment, the filter circuit 20 may be provided.

  Next, the operation of the control device for the self-excited converter according to the present embodiment configured as described above will be described. The main circuit configuration of the self-excited converter in this embodiment is the same as that shown in FIG. 8B as described above, and the operation of the self-excited converter is also the same. Further, the control device for the self-excited converter in the present embodiment is the same as that of the first embodiment shown in FIG. 1 as described above, and the operation of the control device is also the same.

  The only difference from the first embodiment in the operation is that the converter output currents Ia, Ib, and Ic are used instead of the Δ winding currents Irs, Ist, and Itr.

  Other operations are the same as those in the first embodiment, and redundant description is omitted. Further, when the filter circuit 20 is provided, the operation is the same as that of the second embodiment.

  As described above, according to the control device for the self-excited converter according to the third embodiment of the present invention, the same effects as those of the first and second embodiments can be obtained.

  FIG. 4 is a diagram showing a main circuit configuration of a self-excited converter according to Embodiment 4 of the present invention. The main circuit configuration of the self-excited converter according to the first embodiment shown in FIG. 8A is different from the AC current detectors 22a, 22b, and 22c that detect the Δ winding internal currents Irs, Ist, and Itr. It is a point provided with AC current detectors 22d, 22e, and 22f that detect outflow currents Ir, Is, and It to the AC system.

  FIG. 5 is a control block diagram of the control device for the self-excited converter according to the fourth embodiment of the present invention. The difference from the control device shown in FIG. 1 according to the first embodiment described above is that the current input to the three-phase / two-phase conversion circuit 7 is not the Δ winding internal currents Irs, Ist, Itr but the outflow current to the AC system. The points are Ir, Is, and It. That is, in the first embodiment, the Δ winding internal currents Irs, Ist, Itr are input to the three-phase / two-phase conversion circuit 7 and used for the dq axis control, and are also input to the adder 16 to be the zero-phase current. In this embodiment, the Δ winding internal currents Irs, Ist, Itr are used only for zero phase current detection.

  The AC current detectors 22a, 22b, and 22c correspond to the first current detection unit of the present invention, and detect a three-phase current (Δ winding internal currents Irs, Ist, Itr) inside the Δ connection.

  On the other hand, the AC current detectors 22d, 22e, and 22f correspond to the second current detection unit of the present invention, and are three-phase currents (outflow currents to the AC system) that are line currents flowing from the Δ connection to the three-phase AC system. Ir, Is, It) is detected.

  The adder 16 corresponds to the adding unit of the present invention, and calculates the sum of the three-phase currents (Δ winding internal currents Irs, Ist, Itr) detected by the AC current detectors 22a, 22b, 22c.

  The phase detection circuit 6, the 3-phase / 2-phase conversion circuit 7, the coordinate conversion circuit 8, the alternating current control circuit 9, the adders 10a, 10b, and the 2-phase / 3-phase conversion circuit 11 as a whole are included in the control unit of the present invention. Correspondingly, an AC output voltage command value for the self-excited converter is output based on the three-phase currents (flow currents Ir, Is, It to the AC system) detected by the current detectors 22d, 22e, 22f.

  Other configurations are the same as those of the first embodiment, and redundant description is omitted. As in the second embodiment, the filter circuit 20 may be provided. Further, the proportional circuit 17 is not necessarily an essential configuration for the control device of the present invention, as in the first and second embodiments, and can be omitted.

  Next, the operation of the control device for the self-excited converter according to the present embodiment configured as described above will be described.

  First, when the current circulating through the Δ winding connected to the AC system side of the transformer for converter 2 is zero, that is, when the zero-phase current I0 is not generated, the operation is the same as in the first embodiment. The duplicated explanation is omitted.

  Next, a case where a current circulating in the Δ winding connected to the AC system side of the transformer for transformer 2 is generated, that is, a case where a zero-phase current I0 is generated will be described.

  In this case, the currents Irs, Ist, Itr in the Δ winding include a zero-phase component. However, the currents Ir, Is, It flowing out to the AC system do not include a zero phase component. Therefore, the currents Irs, Ist, Itr inside the Δ winding and the currents Ir, Is, It flowing out to the AC system are not equivalent.

  The adder 16, the proportional circuit 17, and the proportional integration circuit 18 to which the currents Irs, Ist, and Itr in the Δ winding are input exhibit the same operations as those in the first embodiment, and thus redundant description is omitted.

  On the other hand, the phase detection circuit 6, the three-phase / two-phase conversion circuit 7, the coordinate conversion circuit 8, the alternating current control circuit 9, the adders 10a and 10b, and the two-phase / three-phase conversion corresponding to the control unit of the present invention as a whole. The circuit 11 outputs an AC output voltage command value for the self-excited converter based on the three-phase current detected by the current detectors 22d, 22e, and 22f, similarly to the conventional control device described with reference to FIG. .

  The three-phase / two-phase conversion circuit 7 performs the calculation shown in the equations (10) and (11) on the input current signal, and even when the input current signal includes a zero-phase component ( The zero-phase component is canceled and output by the calculations shown in equations 10) and (11). Therefore, when the outflow currents Ir, Is, It to the AC system are used and when the currents Irs, Ist, Itr inside the Δ winding are used, the output of the three-phase / two-phase conversion circuit 7 is equivalent, Converter output voltage signals Vac ′, Vbc ′, and Vcc ′ (output signals of the two-phase / three-phase conversion circuit 11), which are outputs of dq axis control, are also equivalent.

  From the above, the 2-phase / 3-phase conversion circuit 11 calculates and adds the converter AC output voltage signals Vac ′, Vbc ′, Vcc ′ corresponding to the AC output voltage command value of the present invention using the equation (4). To the devices 19a, 19b, 19c.

  In addition, since it is necessary to use a current detection value including a zero-phase component for detecting the zero-phase current I0, the current input to the adder 16 is the three currents detected by the AC current detectors 22a, 22b, and 22c. It must be a phase current (Δwinding internal currents Irs, Ist, Itr). Therefore, the adder 16 cannot use the outflow currents Ir, Is, It to the AC system.

  Other operations are the same as those in the first embodiment, and redundant description is omitted. Further, when the filter circuit 20 is provided, the operation is the same as that of the second embodiment.

  As described above, according to the control device for the self-excited converter according to the fourth embodiment of the present invention, the same effects as those of the first and second embodiments can be obtained.

  Further, as described above, conventional self-excited converters and control devices often have the configurations shown in FIGS. 7 (a) and 7 (b). When the present invention shown in the present embodiment is applied to such a conventional apparatus, the AC current detectors 22a, 22b, 22c, the adder 16, Since only the proportional circuit 17, the proportional integration circuit 18, and the adders 19a, 19b, and 19c are added, there is an advantage that the present invention can be easily realized.

  FIG. 6 is a diagram showing a main circuit configuration of a self-excited converter according to Embodiment 5 of the present invention. The difference from the main circuit configuration of the self-excited converter according to the third embodiment shown in FIG. 8B is an AC current detector that detects output currents Ia, Ib, and Ic of the three single-phase converters 1a, 1b, and 1c. In addition to 23a, 23b, and 23c, AC current detectors 22d, 22e, and 22f that detect outflow currents Ir, Is, and It to the AC system are provided.

  Further, the control device for the self-excited converter according to the fifth embodiment of the present invention is the same as the control device according to the fourth embodiment shown in FIG. However, the current input to the adder 16 is not the Δ winding internal currents Irs, Ist, Itr but the output currents Ia, Ib, Ic of the three single-phase converters 1a, 1b, 1c. As described in the third embodiment, this is the standard of the Δ winding currents Irs, Ist, Itr of the converter transformer 2 and the output currents Ia, Ib, Ic of the three single-phase converters 1a, 1b, 1c. This is because the converted values are equivalent.

  The AC current detectors 23a, 23b, and 23c correspond to the first current detection unit of the present invention, and the three-phase currents (output currents Ia, Ib, and Ic) output by the three single-phase converters 1a, 1b, and 1c. Is detected.

  On the other hand, the AC current detectors 22d, 22e, and 22f correspond to the second current detection unit of the present invention, and are three-phase currents (outflow currents to the AC system) that are line currents flowing from the Δ connection to the three-phase AC system. Ir, Is, It) is detected.

  The adder 16 corresponds to the adding unit of the present invention, and calculates the sum of the three-phase currents (single-phase converter output currents Ia, Ib, Ic) detected by the AC current detectors 23a, 23b, 23c.

  The phase detection circuit 6, the 3-phase / 2-phase conversion circuit 7, the coordinate conversion circuit 8, the alternating current control circuit 9, the adders 10a, 10b, and the 2-phase / 3-phase conversion circuit 11 as a whole are included in the control unit of the present invention. Correspondingly, an AC output voltage command value for the self-excited converter is output based on the three-phase currents (flow currents Ir, Is, It to the AC system) detected by the current detectors 22d, 22e, 22f.

  Other configurations are the same as those in the fourth embodiment, and a duplicate description is omitted. As in the second embodiment, the filter circuit 20 may be provided.

  Next, the operation of the control device for the self-excited converter according to the present embodiment configured as described above will be described. As described above, the normalized values of the Δ winding currents Irs, Ist, Itr of the converter transformer 2 and the output currents Ia, Ib, Ic of the three single-phase converters 1a, 1b, 1c are equivalent. Therefore, the control device for the self-excited converter according to the present embodiment exhibits the same operation as that of the fourth embodiment. Note that when the filter circuit 20 is provided, the operation is the same as that of the second embodiment.

  As described above, according to the control device for the self-excited converter according to the fifth embodiment of the present invention, the same effect as that of the fourth embodiment can be obtained.

  INDUSTRIAL APPLICABILITY The present invention is applicable to a control device for a self-excited converter used for a DC power transmission / DC interconnection system, a power supply system, a reactive power compensator, etc.

It is a control block diagram of the control device of the self-excited converter according to Embodiment 1 of the present invention. It is a figure which shows the comparison of the output current waveform of the said self-excited converter by the presence or absence of the control apparatus application of the self-excited converter which concerns on Example 1 of this invention. It is a control block diagram of the control apparatus of the self-excited converter which concerns on Example 2 of this invention. It is a figure which shows the main circuit structure of the self-excited converter which concerns on Example 4 of this invention. It is a control block diagram of the control apparatus of the self-excited converter based on Example 4 of this invention. It is a figure which shows the main circuit structure of the self-excitation converter which concerns on Example 5 of this invention. It is a figure which shows the example of the main circuit structure of the general self-excited converter system connected to a three-phase alternating current system using three single phase converters, and its control block. It is a figure which shows the main circuit structure in the case of detecting a zero phase electric current in the general self-excited converter system connected to a three-phase alternating current system using three single phase converters. It is a general control block diagram in the case of suppressing a zero phase current in a self-excited converter system using three single-phase converters.

Explanation of symbols

1a, 1b, 1c Single-phase converter 2 Converter transformer 3 AC buses 4a, 4b, 4c AC voltage detectors 5a, 5b, 5c AC current detector 6 Phase detection circuit 7 3-phase / 2-phase conversion circuit 8 Coordinate conversion Circuit 9 AC current control circuits 10a, 10b Adder 11 2-phase / 3-phase conversion circuit 12 Pulse generation circuit 13 Current command value calculation circuits 14a, 14b, 14c Sine wave AC current control circuits 15a, 15b, 15c Adder 16 Adder 17 proportional circuit 18 proportional integration circuit 19a, 19b, 19c adder 20 filter circuit 21a, 21b, 21c subtractor 22a, 22b, 22c, 22d, 22e, 22f AC current detector 23a, 23b, 23c AC current detector

Claims (6)

A control device for a self-excited converter that configures a three-phase using three single-phase converters and that is linked to a three-phase AC system via a transformer in which the AC system side winding is Δ-connected,
A current detector for detecting the three-phase current inside the Δ connection;
An adder for calculating the sum of three-phase currents detected by the current detector;
A controller that outputs an AC output voltage command value for the self-excited converter based on the three-phase current detected by the current detector;
A correction unit that performs correction common to each phase on the AC output voltage command value output by the control unit according to the sum of the three-phase currents calculated by the addition unit;
A control device for a self-excited converter, comprising: A control device for a self-excited converter that configures a three-phase using three single-phase converters and that is linked to a three-phase AC system via a transformer in which the AC system side winding is Δ-connected,
A current detector for detecting a three-phase current output by the three single-phase converters;
An adder for calculating the sum of three-phase currents detected by the current detector;
A controller that outputs an AC output voltage command value for the self-excited converter based on the three-phase current detected by the current detector;
A correction unit that performs correction common to each phase on the AC output voltage command value output by the control unit according to the sum of the three-phase currents calculated by the addition unit;
A control device for a self-excited converter, comprising: A control device for a self-excited converter that configures a three-phase using three single-phase converters and that is linked to a three-phase AC system via a transformer in which the AC system side winding is Δ-connected,
A first current detector for detecting a three-phase current inside the Δ connection;
A second current detection unit that detects a three-phase current that is a line current flowing from the Δ connection to the three-phase AC system;
An adder for calculating a sum of three-phase currents detected by the first current detector;
A controller that outputs an AC output voltage command value for the self-excited converter based on the three-phase current detected by the second current detector;
A correction unit that performs correction common to each phase on the AC output voltage command value output by the control unit according to the sum of the three-phase currents calculated by the addition unit;
A control device for a self-excited converter, comprising: A control device for a self-excited converter that configures a three-phase using three single-phase converters and that is linked to a three-phase AC system via a transformer in which the AC system side winding is Δ-connected,
A first current detector for detecting a three-phase current output by the three single-phase converters;
A second current detection unit that detects a three-phase current that is a line current flowing from the Δ connection to the three-phase AC system;
An adder for calculating a sum of three-phase currents detected by the first current detector;
A controller that outputs an AC output voltage command value for the self-excited converter based on the three-phase current detected by the second current detector;
A correction unit that performs correction common to each phase on the AC output voltage command value output by the control unit according to the sum of the three-phase currents calculated by the addition unit;
A control device for a self-excited converter, comprising:   The correction unit is common to each phase with respect to the AC output voltage command value output by the control unit based on a correction value calculated by performing a proportional integration process on the sum of the three-phase currents calculated by the addition unit. The control device for a self-excited converter according to any one of claims 1 to 4, wherein the correction is performed.   The correction unit applies an AC output voltage command value output by the control unit based on a correction value calculated by performing filter processing and proportional integration processing to the sum of the three-phase currents calculated by the addition unit. The control device for a self-excited converter according to any one of claims 1 to 4, wherein correction common to each phase is performed.

Images