JP2019161938A - Control device and control method for power control device - Google Patents

Abstract

A control device of a power conversion device that enables reduction in variation of an exciting current between transformers is provided. A control device of a power conversion device is a control device of a power conversion device that converts DC power into AC power through a plurality of converters and a plurality of transformers, and includes a converter output voltage command transmitted to the plurality of converters. An overall demagnetization suppression control unit 62 including a control element for generating a first correction signal for converging a DC component included in an average value of the exciting current of each of the plurality of transformers to zero as a correction signal to be superimposed on the signal. And a plurality of second correction signals for converging respective exciting currents of the plurality of transformers to an average value of the respective exciting currents as correction signals further superimposed on the first correction signal. An individual magnetization suppression control unit 63 including a control element. [Selection] Figure 2

Description

  Embodiments described herein relate generally to a control device and a control method for a power conversion device.

  A multiple power conversion device formed by multiplexing a converter and a transformer is configured by connecting a plurality of converters in series via a plurality of transformers, and can output a high voltage of several kV to several hundreds kV. Further, by shifting the switching timing of each converter, the output harmonic voltage can be reduced, and a smooth current with a small ripple can be supplied to the load. For this reason, the multiple power conversion device is used for various applications such as a power system voltage stabilizing device, a railway vehicle, and an industrial drive device.

  In such a multiple power converter, there is a possibility that the magnetic flux in the transformer core is biased in one direction due to the DC voltage component included in the output voltage or load system voltage of the converter, and the transformer is magnetically saturated. is there. When the transformer is magnetically saturated, the inductance component of the transformer core becomes close to zero, so that the excitation current of the transformer increases and an excessive current flows through the converter. This current may lead to destruction of the switching devices constituting the converter. Therefore, power converters are generally provided with a protection function that detects an overcurrent and stops the converter. However, frequent stoppage of the power conversion device by this protection function lowers the device operation rate and causes economic loss.

  As a technique for solving such a problem, there is a technique of DC demagnetization suppression control that suppresses DC demagnetization of a transformer of a multiple power converter. With this technique, it is possible to avoid magnetic saturation of the transformer by detecting the excitation current of the transformer at each stage and adjusting the converter output voltage in a direction in which the excitation current is reduced.

JP-A-7-28534 JP 2003-274675 A

  In the technique of DC bias suppression control, generally, a DC component of a transformer exciting current is detected, and a DC bias correction amount is superimposed on a converter output voltage command value so that the DC component becomes zero.

  However, since a filter is used to detect the direct current component of the excitation current, there is a control dead time and a delay occurs in the control response. In this case, if the gain is adjusted so that the control response becomes large, the control response may vibrate and become unstable. As described above, since there is a limit to the adjustment of the control response of the DC demagnetization suppression control, the output voltage may vary among the converters, which may cause the exciting current to vary among the transformers. is there.

  Moreover, in the steady state, the variation in the excitation current is small, and there is no possibility that the transformer will be magnetically saturated until an overcurrent is reached, but the excitation current of the transformer in each stage is caused by, for example, a sudden unbalance of the load system voltage. When the variation in the value becomes large, the excitation current of a certain converter may reach an overcurrent.

  Problem to be solved by the invention is providing the control apparatus and control method of a power converter device which makes it possible to reduce the dispersion | variation in the excitation current between transformers.

  According to the embodiment, a control device for a power conversion device that converts DC power into AC power through a plurality of converters and a plurality of transformers, the correction signal being superimposed on a converter output voltage command signal to be sent to the plurality of converters An overall demagnetization suppression control unit including a control element for generating a first correction signal for converging a DC component included in an average value of excitation currents of each of the plurality of transformers to zero, and the first correction signal As a correction signal further superimposed on the individual magnetic field, the individual bias suppression including a plurality of control elements for generating a second correction signal for converging the respective excitation currents of the plurality of transformers to the average value of the respective excitation currents And a control unit for the power conversion device including the control unit.

  According to the embodiment, it is possible to reduce variations in excitation current between transformers.

The figure which shows the structural example of the power converter device with which the control apparatus which concerns on one Embodiment is applied. The figure which shows an example of a function structure of the control apparatus of the embodiment. The figure which shows an example of a structure for implement | achieving direct current | flow magnetic-bias suppression control by the control apparatus of the embodiment. The waveform graph which shows the relationship between the secondary current of a 1st-stage transformer of U phase, and a primary current, and the relationship between the secondary current of a U-phase 2nd stage transformer, and a primary current. The waveform graph which shows the relationship between the excitation current of the 1st-stage transformer of U phase, the excitation current of the 2nd-stage transformer of U phase, and the average of the excitation current of all the U-phase transformers. The waveform graph which shows the relationship between the correction voltage command value which suppresses the magnetization of the 1st-stage transformer of U phase, and the correction voltage command value which suppresses the magnetization of the 2nd-stage transformer of U phase. U-phase reference converter output voltage command value, converter output voltage command value for U-phase first stage converter, and converter output voltage command value vref_u2 for U-phase second-stage converter Waveform graph shown.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration example of a power conversion device to which a control device according to an embodiment is applied.

  The power converter according to the present embodiment includes a set of a converter and a plurality of transformers configured in a plurality of stages for each of the U-phase, V-phase, and W-phase of three-phase AC, and through these, DC power is converted into AC power. Convert to Here, a case where a set of a converter and a plurality of transformers is configured in two stages for each of the U-phase, V-phase, and W-phase of the three-phase AC is illustrated.

  More specifically, for example, as shown in FIG. 1, the multiple power conversion device includes converters 11 and 12 (cnv_u2, cnv_u1) and transformers 21 and 22 provided corresponding to a U-phase load 31 (l_u). (Tr_u2, tr_u1), converters 13 and 14 (cnv_v2, cnv_v1) and transformers 23 and 24 (tr_v2, tr_v1) provided corresponding to the V-phase load 32 (l_v), and a W-phase load 33 (l_w) ) And converters 15 and 16 (cnv_w2, cnv_w1) provided in correspondence with each other, thereby converting the DC voltage v_dc supplied from the DC power supply 10 into a three-phase AC voltage, and loads 31 to 33 (l_u, l_v, l_w).

  As shown in FIG. 1, the DC power supply 10 that supplies the DC voltage v_dc includes input terminals of U-phase converters 11 and 12 (cnv_u2, cnv_u1) and V-phase converters 13 and 14 (cnv_v2, cnv_v1). The input terminal is connected to each input terminal of W-phase converters 15 and 16 (cnv_w2, cnv_w1).

  The output terminal of the U-phase converter 11 (u2) is connected to the secondary side of the U-phase transformer 21 (tr_u2), and the output terminal of the U-phase converter 12 (u1) is connected to the U-phase transformer 22 ( It is connected to the secondary side of tr_u1). Of the transformers 21 and 22 (tr_u2, tr_u1), the primary negative terminal of the transformer 22 (tr_u1) on the low voltage side is connected to the reference potential point, and the primary side positive terminal of the transformer 22 (tr_u1) is connected. The terminal is connected to the negative terminal on the primary side of the transformer 21 (tr_u2), and the positive terminal on the primary side of the transformer 21 (tr_u2) is connected to the load 31 (l_u).

  Thus, by connecting the transformers 21 and 22 (tr_u2, tr_u1) of each stage in series, a high AC voltage obtained by adding the voltage of the converter 11 (cnv_u2) and the voltage of the converter 12 (cnv_u1) is added to the load 31 ( l_u).

  The V phase and the W phase have the same configuration as the U phase described above, and are different only in that the phase of the output AC voltage is shifted by 120 degrees.

  Here, the case where the number of multiplexing (number of stages) is 2 is illustrated, but by increasing the number of multiplexing (number of stages) to 3 or more, the number of series is further increased, and the AC voltage output is further increased. It may be configured.

  The multiplex power converter further includes currents for detecting the values of secondary currents i_u2, i_u1, i_v2, i_v1, i_w2, i_w1 of transformers 21 to 26 (tr_u2, tr_u1, tr_v2, tr_v1, tr_w2, tr_w1), respectively. Detectors 41 to 46 and current detectors 51 to 53 for detecting values of primary currents i_u, i_v, i_w of transformers 21, 23, 25 (r_u2, tr_v2, tr_w2), respectively, are installed.

  The current value detected by each current detector is transmitted to the control device 1 provided in the multiple power conversion device.

  The control device 1 controls the converter output voltage command values Vref_u2, Vref_u1, Vref_v2, Vref_v1, Vs for the converters 11 to 16 (cnv_u2, cnv_u1, cnv_v2, cnv_w2, cnv_w1) in accordance with the power command from the host system. Vref_w2 and Vref_w1 are supplied, and can be generated by the transformers 21 to 26 (tr_u2, tr_u1, tr_v2, tr_v1, tr_w2, tr_w1) based on the current values detected by the current detectors 41 to 46 and 51 to 53, respectively. The converter output voltage command values Vref_u1, Vref_u2, Vref_v1, Vref_v2, Vref_w1, and Vref_w2 are adjusted so that the DC bias is suppressed and the variation in the excitation current between the transformers of each phase is suppressed.

  Here, an example of a functional configuration of the control device 1 is shown in FIG.

The control device 1 includes functions of a signal receiving unit 61, an overall demagnetization suppression control unit 62, an individual demagnetization suppression control unit 63, a signal transmission unit 64, and the like.
The control device 1 performs direct current bias suppression control for suppressing direct current bias of each transformer of the multiple power converter. DC bias suppression control is divided into overall bias suppression control and individual bias suppression control. The overall demagnetization suppression control is performed by the overall demagnetization suppression control unit 62, and the individual demagnetization suppression control is performed by the individual demagnetization suppression control unit 63.

  The signal receiving unit 61 receives the secondary currents i_u2, i_u1, i_v2, i_v1, i_w2, i_w1 values of the transformers 21 to 26 (tr_u2, tr_u1, tr_v2, tr_v1, tr_w2, tr_w1) detected by the current detectors 41 to 46. Is a function of receiving signals indicating primary currents i_u, i_v, i_w of transformers 21, 23, 25 (r_u2, tr_v2, tr_w2) detected by current detectors 51-53. is there.

  Based on the current values detected by the current detectors 41 to 46 and the current values detected by the current detectors 51 to 53, the overall bias suppression control unit 62 is based on the value of the excitation current of each transformer. DC bias of the whole transformers 21 and 22 (tr_u2, tr_u1), DC bias of the V phase transformers 23 and 24 (tr_v2, tr_v1), and W phase transformers 25 and 26 (tr_w2, tr_w1) ) This is a function for performing control (overall bias suppression control) for suppressing overall DC bias.

  For example, the overall bias suppression control unit 62 sends the converter output voltage to the U-phase converters 11 and 12 (cnv_u2, cnv_u1) in order to suppress the DC bias of the U-phase transformers 21 and 22 (tr_u2, tr_u1). As a correction signal to be superimposed on the command signal, a first correction signal (for U-phase) that converges the DC component included in the average value of the respective excitation currents of the U-phase transformers 21 and 22 (tr_u2, tr_u1) to zero. A control element for generating

  Similarly, the overall bias suppression control unit 62 sends the converter output to the V-phase converters 13 and 14 (cnv_v2, cnv_v1) in order to suppress the DC bias of the V-phase transformers 23 and 24 (tr_v2, tr_v1). As a correction signal to be superimposed on the voltage command signal, a first correction signal (for V-phase) that converges the DC component included in the average value of the respective excitation currents of the V-phase transformers 23 and 24 (tr_v2, tr_v1) to zero. ) To generate a control element.

  Similarly, the overall demagnetization suppression control unit 62 outputs the converter output to the W-phase converters 15 and 16 (cnv_w2, cnv_w1) in order to suppress the DC demagnetization of the W-phase transformers 25 and 26 (tr_w2, tr_w1). As a correction signal to be superimposed on the voltage command signal, a first correction signal (for W phase) that converges the DC component included in the average value of the respective excitation currents of the W phase transformers 25 and 26 (tr_w2, tr_w1) to zero. ) To generate a control element.

  Based on the current value detected by the current detectors 41 to 46 and the current value detected by the current detectors 51 to 53, the individual bias suppression control unit 63 is based on the value of the excitation current of each transformer. Variation in DC bias between the transformers 21 and 22 (tr_u2, tr_u1), variation in DC bias between the V-phase transformers 23 and 24 (tr_v2, tr_v1), and W-phase transformers 25 and 26 This is a function of performing control (individual bias suppression control) for suppressing the variation of DC bias between (tr_w2, tr_w1). The individual demagnetization suppression control unit 63 does not use a signal that has passed through a filter that causes a control dead time for control, and uses only a signal that does not pass through the filter for control.

  For example, the individual demagnetization suppression control unit 63 further controls the first correction signal (for U phase) in order to suppress variation in DC demagnetization between the U phase transformers 21 and 22 (tr_u2, tr_u1). As a correction signal to be superimposed, a second correction signal (for U phase) for converging the respective excitation currents of the U-phase transformers 21 and 22 (tr_u2, tr_u1) to the average value of the respective excitation currents is used. Two control elements generated for each excitation current are included.

  Similarly, the individual demagnetization suppression control unit 63 controls the first correction signal (for V-phase) in order to suppress variation in DC demagnetization between the V-phase transformers 23 and 24 (tr_v2, tr_v1). Further, as a correction signal to be superimposed, a second correction signal (for V-phase) for converging the respective excitation currents of the V-phase transformers 23 and 24 (tr_v2, tr_v1) to the average value of the respective excitation currents. It includes two control elements generated for each excitation current.

  Similarly, the individual demagnetization suppression control unit 63 controls the first correction signal (for W phase) in order to suppress variation in DC demagnetization between the W phase transformers 25 and 26 (tr_w2, tr_w1). Furthermore, as correction signals to be superimposed, second correction signals (for the W phase) for converging the respective excitation currents of the W-phase transformers 25 and 26 (tr_w2, tr_w1) to the average values of the respective excitation currents, respectively. It includes two control elements generated for each excitation current.

  The signal transmission unit 64 superimposes the first correction signal and the second correction signal on the converter output voltage command (reference value) for each converter based on the power command from the host system. This is a function for transmitting the voltage command values Vref_u1, Vref_u2, Vref_v1, Vref_v2, Vref_w1, Vref_w2 to converters 11 to 16 (cnv_u2, cnv_u1, cnv_v2, cnv_v1, cnv_w2, cnv_w1), respectively.

  FIG. 3 is a diagram illustrating an example of a configuration for realizing the direct-current demagnetization suppression control by the control device 1. Here, only the configuration related to the U phase among the U phase, the V phase, and the W phase is illustrated.

  The control device 1 includes, for example, subtraction units 71 and 72, addition unit 73, multiplication unit 74, low-pass filter 75, proportional integration control unit 76, subtraction units 81 and 91, proportional integration control units 82 and 92, and subtraction units 83 and 93. , Subtracting units 84 and 94 are included.

  The subtracting unit 71 subtracts the primary current value i_u from the secondary current value i_u1 of the transformer tr_u1 to calculate a value i_m_u1 of the exciting current (U-phase 1-stage exciting current) of the transformer tr_u1. Similarly, the subtraction unit 72 subtracts the primary current value i_u from the secondary current value i_u2 of the transformer tr_u2 to calculate a value i_m_u2 of the exciting current (U-phase two-stage exciting current) of the transformer tr_u2.

  The adding unit 73 adds the value i_m_u1 of the U-phase one-stage excitation current and the value i_m_u2 of the U-phase two-stage excitation current, and outputs the addition result. Multiplier 74 multiplies the addition result by 0.5 (or divides by 2), and outputs U-phase excitation current value i_m_u. That is, the combination of the adding unit 73 and the multiplying unit 74 calculates an average value of the excitation currents of the U-phase transformers tr_u1 and tr_u2.

  Here, the case where the number of multiplexes (number of stages) is 2 is illustrated, but when the number of multiplexes (number of stages) is n (n: an integer of 3 or more), the adding unit 73 generates n excitation currents. It is assumed that values are added, and the multiplication unit 74 multiplies the addition result by 1 / n (or divides by n).

  The filter 75 extracts the excitation current DC component (U-phase excitation current DC component) i_m_u_dc of the transformers tr_u1 and tr_u2 from the value i_m_u of the U-phase excitation current output from the adder 73. As this filter 75, a general low-pass filter (a filter that allows a signal having a frequency lower than a certain frequency to pass) may be applied. In order to detect the DC component more accurately, for example, for a certain period of the signal The moving average (for example, the moving average of the AC output voltage period) may be replaced with a moving average filter that sequentially outputs the moving average.

  The proportional-plus-integral control unit 76 constitutes at least a part of the overall demagnetization suppression control unit 62 described above. The proportional-integral control unit 76 is a control element that realizes overall bias suppression control, and performs, for example, a proportional-integral calculation PI to converge the U-phase excitation current DC component i_m_u_dc to zero, and is used for a U-phase converter. A U-phase bias suppression suppression voltage command value vref_m_u (corresponding to the above-described first correction signal (for U-phase)) is generated as a correction value for the U-phase converter output voltage command value (reference value) vref_u. Note that the proportional integral gain used for the proportional integral calculation PI is set within a range in which the control system is stable in consideration of the phase delay of the low-pass filter 75 (or moving average filter).

  The subtraction unit 81, the proportional integration control unit 82, the subtraction unit 83, and the subtraction unit 84 constitute a part of the above-described individual bias suppression control unit 63. Similarly, the subtraction unit 91, the proportional integration control unit 92, the subtraction unit 93, and the subtraction unit 94 also constitute a part of the above-described individual bias suppression control unit 63.

  The subtraction unit 81 subtracts the U-phase one-stage excitation current value i_m_u1 calculated by the subtraction unit 71 from the U-phase excitation current value i_m_u calculated by the multiplication unit 74, and the U-phase excitation current value i_m_u and U The difference from the phase i stage excitation current value i_m_u1 is output.

  The proportional-integral control unit 82 performs, for example, the proportional-integral calculation PI1 in order to converge the difference between the U-phase excitation current value i_m_u and the U-phase one-stage excitation current value i_m_u1 to zero, and suppresses the above-described U-phase demagnetization suppression. A correction value (corresponding to one of the above-described second correction signals (for U-phase)) is generated for the correction voltage command value vref_m_u. The subtraction unit 83 subtracts the generated correction value from the U-phase bias suppression suppression voltage command value vref_m_u, and corrects the U-phase converter output voltage command value (reference value) ref_u (U-phase one-stage bias suppression). Correction voltage command value) vref_m_u1 is generated.

  The subtracting unit 84 subtracts the generated correction value (U-phase one-stage demagnetization suppression correction voltage command value) vref_m_u1 from the U-phase converter output voltage command value (reference value) vref_u, for the U-phase one-stage converter cnv_u1 Converter output voltage command value vref_u1 is generated.

  Similarly, the subtraction unit 91 subtracts the U-phase two-stage excitation current i_m_u2 calculated by the subtraction unit 72 from the U-phase excitation current value i_m_u calculated by the multiplication unit 74 to obtain the U-phase excitation current value i_m_u. The difference from the value i_m_u2 of the U-phase two-stage excitation current is output.

  The proportional-integral control unit 92 performs, for example, the proportional-integral calculation PI2 in order to converge the difference between the U-phase excitation current value i_m_u and the U-phase two-stage excitation current value i_m_u2 to zero, and suppresses the above-described U-phase magnetization demagnetization. A correction value (corresponding to one of the above-described second correction signals (for U-phase)) is generated for the correction voltage command value vref_m_u. The proportional integral control unit 92 is set to have a control gain larger than that of the proportional integral control unit 76 described above. The subtractor 93 subtracts the generated correction value from the U-phase bias suppression suppression voltage command value vref_m_u, and corrects the U-phase converter output voltage command value (reference value) vref_u (a U-phase two-stage bias suppression). Correction voltage command value) vref_m_u2 is generated.

  The subtracting unit 94 subtracts the generated correction value (U-phase two-stage demagnetization suppression correction voltage command value) vref_m_u2 from the U-phase converter output voltage command value (reference value) vref_u, for the U-phase two-stage converter cnv_u2 The converter output voltage command value vref_u2 is generated.

  The above-described proportional-integral control units 82 and 92 do not use a signal that has passed through a low-pass filter or the like that causes a control dead time for control. Therefore, the proportional-integral control units 82 and 92 do not cause a large delay in the control response, and even if the gain is adjusted so that the control response becomes large, the possibility that the control response vibrates and becomes unstable is low. For example, by setting the control gains of the proportional integral control units 82 and 92 to be larger than the control gain of the proportional integral control unit 76, the control response is accelerated, and the excitation current between the U-phase transformers is increased. Variations can be suppressed with higher accuracy.

  Note that the V phase and the W phase have the same configuration as the U phase described above.

  During the operation of the multiplex power conversion device configured as described above, the individual current values detected by the current detectors 41 to 46 and the current detectors 51 to 53 shown in FIG. Is transmitted. In the control device 1, the transformers 21 to 26 (tr_u2, tr_u1, tr_v2, tr_v1, tr_w2, tr_w1) based on the individual current values detected by the current detectors 41 to 46 and the current detectors 51 to 53. Is supplied to the converters 11 to 16 (cnv_u2, cnv_u1, cnv_v2, cnv_v1, cnv_w2, cnv_w1) so that the DC bias that can occur in the transformer is suppressed and the variation of the excitation current between the transformers of each phase is suppressed. Converter output voltage command values Vref_u1, Vref_u2, Vref_v1, Vref_v2, Vref_w1, and Vref_w2 are adjusted.

  For example, for the U phase, as shown in FIG. 3, the subtraction unit 71 subtracts the primary current value i_u from the secondary current value i_u1 of the transformer tr_u1 to calculate the U phase 1-stage excitation current value i_m_u1. Is done. Similarly, the subtractor 72 subtracts the primary current value i_u from the secondary current value i_u2 of the transformer tr_u2 to calculate the U-phase two-stage excitation current value i_m_u2.

  Here, the relationship between the secondary current value i_u1 of the transformer tr_u1 and the primary current value i_u and the relationship between the secondary current value i_u2 of the transformer tr_u2 and the primary current value i_u are shown in the waveform of FIG. Shown in the graph.

  The difference between the secondary current value i_u1 of the transformer tr_u1 and the primary current value i_u shown in the waveform graph of FIG. 4 corresponds to the value i_m_u1 of the excitation current (U-phase one-stage excitation current) of the transformer tr_u1. The difference between the secondary current value i_u2 of the transformer tr_u2 and the primary current value i_u corresponds to the value i_m_u2 of the excitation current (U-phase two-stage excitation current) of the transformer tr_u2.

  Next, the adding unit 73 adds the value i_m_u1 of the U-phase one-stage excitation current and the value i_m_u2 of the U-phase two-stage excitation current, and outputs the addition result. In addition, the multiplication unit 74 multiplies the addition result by 0.5, and outputs a U-phase excitation current value i_m_u. That is, here, the average value of the excitation currents of the U-phase transformers tr_u1 and tr_u2 is calculated.

  Here, the relationship among the value i_m_u1 of the U-phase one-stage exciting current, the value i_m_u2 of the U-phase two-stage exciting current, and the value i_m_u of the U-phase exciting current is shown in the waveform graph of FIG.

  From the waveform graph of FIG. 5, it can be seen that the average value of the value i_m_u1 of the U-phase one-stage excitation current and the value i_m_u2 of the U-phase two-stage excitation current corresponds to the value i_m_u of the U-phase excitation current.

  Next, the filter 75 extracts the excitation current DC component (U-phase excitation current DC component) i_m_u_dc of the transformers tr_u1 and tr_u2 from the value i_m_u of the U-phase excitation current output from the adder 73. Further, in the proportional-plus-integral control unit 76, for example, a proportional-integral calculation PI is performed in order to converge the U-phase exciting current DC component i_m_u_dc to zero, and a correction value for the U-phase converter output voltage command value (reference value) vref_u is obtained. A U-phase bias suppression suppression voltage command value vref_m_u is generated.

  On the other hand, in the subtracting unit 81, the value i_m_u1 of the U-phase one-stage excitation current calculated by the subtracting unit 71 is subtracted from the value i_m_u of the U-phase exciting current calculated by the multiplying unit 74 to obtain the value of the U-phase exciting current. The difference between i_m_u and the value i_m_u1 of the U-phase one-stage excitation current is output. Further, in the proportional-plus-integral control unit 82, for example, a proportional-integral calculation PI1 is performed in order to converge the difference to zero, and a correction value for the above-described U-phase demagnetization suppression correction voltage command value vref_m_u is generated. Further, the subtraction unit 83 subtracts the generated correction value from the U-phase bias suppression suppression voltage command value vref_m_u, and corrects the U-phase converter output voltage command value (reference value) ref_u with a correction value (U-phase one-stage bias). Magnetic suppression correction voltage command value) vref_m_u1 is generated.

  Similarly, in the subtractor 91, the U-phase two-stage excitation current i_m_u2 calculated by the subtractor 72 is subtracted from the U-phase excitation current value i_m_u calculated by the multiplier 74, and the U-phase excitation current value i_m_u is subtracted. And the difference between the U phase two-stage excitation current value i_m_u2. Further, in the proportional-integral control unit 92, for example, a proportional-integral calculation PI2 is performed in order to converge the difference to zero, and a correction value for the above-described U-phase bias suppression suppression voltage command value vref_m_u is generated. Further, the subtraction unit 93 subtracts the generated correction value from the U-phase bias suppression suppression voltage command value vref_m_u, and corrects the U-phase converter output voltage command value (reference value) vref_u with a correction value (U-phase two-stage bias). Magnetic suppression correction voltage command value) vref_m_u2 is generated.

  Here, the relationship between the U-phase first-stage demagnetization suppression voltage command value vref_m_u1 and the U-phase second-stage demagnetization suppression correction voltage command value vref_m_u2 is shown in the waveform graph of FIG.

  From the waveform graph of FIG. 6, a U-phase one-stage bias suppression suppression voltage command value vref_m_u1 for the U-phase one-stage converter cnv_u1, and a U-phase two-stage bias suppression suppression voltage command value vref_m_u2 for the U-phase converter cnv_u2 Are different values and are generated individually for each converter.

  Next, the subtraction unit 84 subtracts the correction value (U-phase one-stage demagnetization suppression correction voltage command value) vref_m_u1 generated by the subtraction unit 83 from the U-phase converter output voltage command value (reference value) vref_u. A converter output voltage command value vref_u1 for the phase one-stage converter cnv_u1 is generated. Similarly, the subtraction unit 94 also subtracts the correction value (U-phase two-stage demagnetization suppression voltage command value) vref_m_u2 generated by the subtraction unit 93 from the U-phase converter output voltage command value (reference value) vref_u. Converter output voltage command value vref_u2 for U-phase two-stage converter cnv_u2 is generated.

  Here, U-phase converter output voltage command value (reference value) vref_u, converter output voltage command value vref_u1 for U-phase one-stage converter cnv_u1, converter output voltage command value vref_u2 for U-phase two-stage converter cnv_u2, and The relationship is shown in the waveform graph of FIG.

  From the waveform graph of FIG. 7, the converter output voltage command value vref_u1 for the U-phase one-stage converter cnv_u1 and the converter output voltage command value vref_u2 for the U-phase two-stage converter cnv_u2 are It can be seen that the reference value is different from vref_u, and is a value generated individually for each converter.

  Converter output voltage command values vref_u1 and vref_u2 generated in this way are individually supplied to converters 11 and 12 (cnv_u2, cnv_u1), respectively.

  Thereby, converters 11 and 12 (cnv_u2, cnv_u1) generate output voltages corresponding to converter output voltage command values vref_u1 and vref_u2, respectively. Since the converter output voltage command values vref_u1 and vref_u2 suppress variations in output voltage between the converters 11 and 12 (cnv_u2, cnv_u1), variations in excitation current between transformers are also suppressed.

  Note that the V-phase and W-phase operations are the same as those of the U-phase described above.

  As described above, according to the present embodiment, in addition to the overall demagnetization suppression control, it is possible to suppress variations in DC demagnetization between the transformers in each phase of the three-phase AC by performing individual demagnetization suppression control. And magnetic saturation of each transformer can be avoided.

  In the individual bias suppression control of the present embodiment, a signal that has passed through a filter that causes a control dead time is not used for the control. For example, each control element that performs individual bias suppression control for each phase of a three-phase alternating current does not use a signal that has passed through a low-pass filter or the like that causes a control dead time for control. Therefore, the individual control elements that perform the individual bias suppression control do not cause a large delay in the control response, and even if the gain is adjusted so that the control response becomes large, the control response vibrates and becomes unstable. Probability is low, for example, by setting the control gain of each control element larger than the control gain of the control element that implements the overall bias suppression control, for example, the control response is quickened, resulting from switching, etc. It is possible to suppress the variation in the excitation current between the transformers with higher accuracy.

  As described above in detail, according to the embodiment, it is possible to reduce variations in excitation current between transformers.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Control apparatus, 10 ... DC power supply, 11-16 ... Converter, 21-26 ... Transformer, 31-33 ... Load, 41-46, 51-53 ... Current detector, 61 ... Signal receiving part, 62 ... Whole Demagnetization suppression control unit, 63 ... Individual demagnetization suppression control unit, 64 ... Signal transmission unit.

Claims (7)

A control device for a power converter that converts DC power into AC power through a plurality of converters and a plurality of transformers,
Control for generating a first correction signal for converging a direct current component included in an average value of excitation currents of the plurality of transformers to zero as a correction signal superimposed on a converter output voltage command signal to be sent to the plurality of converters An overall demagnetization suppression control unit including elements;
A plurality of control elements for generating a second correction signal for converging the respective excitation currents of the plurality of transformers to an average value of the respective excitation currents as correction signals further superimposed on the first correction signal Including an individual demagnetization suppression control unit,
A control device for a power conversion device. Each of the plurality of control elements included in the individual demagnetization suppression control unit has a control gain set larger than that of the control element included in the overall demagnetization suppression control unit.
The control apparatus of the power converter device of Claim 1. Each of the plurality of control elements included in the individual demagnetization suppression control unit performs PI control or PID control.
The control apparatus of the power converter device of Claim 1 or 2. The overall demagnetization suppression control unit is
By using a low-pass filter, a direct current component is extracted from the average value of the respective excitation currents of the plurality of transformers.
The control apparatus of the power converter device of any one of Claims 1 thru | or 3. The overall demagnetization suppression control unit is
By using a moving average filter, a direct current component is extracted from an average value of each exciting current of the plurality of transformers.
The control apparatus of the power converter device of any one of Claims 1 thru | or 4. The individual demagnetization suppression control unit does not use a signal that has passed through a filter that causes control dead time for control, and uses only a signal that does not pass through the filter for control.
The control apparatus of the power converter device of any one of Claims 1 thru | or 5. A method for controlling a power converter that converts DC power into AC power through a plurality of converters and a plurality of transformers,
A first control unit causes a direct current component included in an average value of excitation currents of the plurality of transformers to converge to zero as a correction signal superimposed on a converter output voltage command signal to be sent to the plurality of converters. Generate a correction signal for
As a correction signal further superimposed on the first correction signal by the second control unit, a second correction signal for converging the respective excitation currents of the plurality of transformers to the average value of the respective excitation currents. Generate
Comprising
Control method of power converter.