JP6906464B2 - Power converter control device and control method - Google Patents

Description

Embodiments of the present invention relate to a control device and a control method of a power conversion device.

A multiplex power converter obtained 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 hundred kV. Further, by shifting the switching timing of each converter, the output harmonic voltage can be reduced, and a smooth current with small ripple can be supplied to the load. Therefore, the multiplex power conversion device is used in various applications such as a power system voltage stabilizer, a railroad vehicle, and an industrial drive device.

In such a multiplex power converter, the magnetic flux in the transformer core may be biased in one direction due to the DC voltage component contained in the output voltage of the converter and the load system voltage, and the transformer may be magnetically saturated. be. When the transformer is magnetically saturated, the inductance component of the transformer core becomes close to zero, so that the exciting current of the transformer increases and an excessive current flows through the converter. This current can lead to the destruction of the switching devices that make up the converter. Therefore, the power converter is generally provided with a protection function that detects an overcurrent and stops the converter. However, frequent outages of the power converter due to this protection function reduce the equipment utilization rate and cause economic loss.

As a technique for solving such a problem, there is a technique of DC demagnetization suppression control for suppressing the 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 exciting current of the transformer in each stage and adjusting the converter output voltage in a direction in which the exciting current is reduced.

Japanese Unexamined Patent Publication No. 7-28534 Japanese Unexamined Patent Publication No. 2003-274675

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

However, since the filter is used to detect the DC component of the exciting current, there is a waste time in control 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. Since there is a limit to the adjustment of the control response of the DC demagnetization suppression control in this way, the output voltage may vary between converters, and as a result, the exciting current may vary between transformers. be.

Further, in the steady state, the variation of the exciting current is small, and there is no possibility that the transformer is magnetically saturated until the overcurrent occurs. However, for example, the exciting current of the transformer in each stage due to the sudden imbalance of the load system voltage. If the variation becomes large, the exciting current of a certain converter may reach an overcurrent.

An object to be solved by the present invention is to provide a control device and a control method for a power conversion device that can reduce variations in exciting currents between transformers.

According to the embodiment, it 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 as a correction signal superimposed on a converter output voltage command signal sent to the plurality of converters. An overall demagnetization suppression control unit including a control element that generates a first correction signal that converges the DC component included in the average value of the exciting currents of the plurality of transformers to zero, and the first correction signal. Individual demagnetization suppression including a plurality of control elements that generate a second correction signal that converges the exciting currents of the plurality of transformers to the average value of the respective exciting currents as correction signals further superimposed on the transformer. A power conversion device comprising a control unit , wherein the individual demagnetization suppression control unit uses only signals that do not pass through the filter, excluding signals that have passed through the filter that causes wasteful time in control, for control. A control device is provided.

According to the embodiment, it is possible to reduce the variation in the exciting current between the transformers.

The figure which shows the structural example of the power conversion apparatus to which the control apparatus which concerns on one Embodiment is applied. The figure which shows an example of the functional structure of the control device of the same embodiment. The figure which shows an example of the structure for realizing the DC demagnetization suppression control by the control device of the same embodiment. A waveform graph showing the relationship between the secondary current and the primary current of the first stage transformer of the U phase and the relationship between the secondary current and the primary current of the second stage transformer of the U phase. A waveform graph showing the relationship between the exciting current of the first stage transformer of the U phase, the exciting current of the second stage transformer of the U phase, and the average exciting current of all the transformers of the U phase. A waveform graph showing the relationship between the correction voltage command value for suppressing the demagnetization of the first stage transformer of the U phase and the correction voltage command value for suppressing the demagnetization of the second stage transformer of the U phase. The relationship between the converter output voltage command value that is the reference for the U phase, the converter output voltage command value for the first stage converter of the U phase, and the converter output voltage command value vref_u2 for the second stage converter of the U phase. Waveform graph shown.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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

The power conversion device 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 three-phase AC U-phase, V-phase, and W-phase, and DC power is converted into AC power through these. Convert to. Here, an example is illustrated in which a converter and a plurality of transformers are configured in two stages for each of the three-phase alternating current U-phase, V-phase, and W-phase.

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

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

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 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 negative terminal on the primary side of the transformer 22 (tr_u1) on the low voltage side is connected to the reference potential point and is positive on the primary side of the transformer 22 (tr_u1). 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).

By connecting the transformers 21 and 22 (tr_u2, tr_u1) in each stage in series in this way, a high AC voltage, which is the sum of the voltage of the converter 11 (cnv_u2) and the voltage of the converter 12 (cnv_u1), is applied to the load 31 ( It is supplied to l_u).

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

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

In the multiple power converter, the currents for detecting the values of the secondary currents i_u2, i_u1, i_v2, i_v1, i_w2, i_w1 of the 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 that detect the values of the primary currents i_u, i_v, and i_w of the transformers 21, 23, 25 (r_u2, tr_v2, tr_w2) are installed.

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

The control device 1 responds to the power command from the host system for the converter output voltage command values Vref_u2, Vref_u1, Vref_v2, Vref_v1, respectively, for the converters 11 to 16 (cnv_u2, cnv_u1, cnv_v2, cnv_v1, cnv_w2, cnv_w1) of each stage. While supplying Vref_w2 and Vref_w1, it can occur in 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 41-46 and 51-53, respectively. The converter output voltage command values Vref_u1, Vref_u2, Vref_v1, Vref_v2, Vref_w1, Vref_w2 are adjusted so that the DC bias is suppressed and the variation in the exciting current between the transformers of each phase is suppressed.

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

The control device 1 includes functions such as a signal receiving unit 61, an overall demagnetization suppression control unit 62, an individual demagnetization suppression control unit 63, and a signal transmission unit 64.
The control device 1 implements DC demagnetization suppression control for suppressing the DC demagnetization of each transformer of the multiple power conversion device. The DC demagnetization suppression control is divided into an overall demagnetization suppression control and an individual demagnetization suppression control. The total demagnetization suppression control is performed by the total 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 is the secondary current i_u2, i_u1, i_v2, i_v1, i_w2, i_w1 value 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. With the function to receive the signal indicating the value of the primary current i_u, i_v, i_w of the transformers 21, 23, 25 (r_u2, tr_v2, tr_w2) detected by the current detectors 51 to 53. be.

The overall demagnetization suppression control unit 62 is a U-phase based on the value of the exciting current of each transformer obtained from the current value detected by the current detectors 41 to 46 and the current value detected by the current detectors 51 to 53. Transformers 21 and 22 (tr_u2, tr_u1) as a whole DC demagnetization, V-phase transformers 23 and 24 (tr_v2, tr_v1) as a whole DC demagnetization, and W-phase transformers 25 and 26 (tr_w2, tr_w1) ) It is a function to perform control to suppress the entire DC demagnetization (total demagnetization suppression control).

For example, the overall demagnetization 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 demagnetization of the U-phase transformers 21 and 22 (tr_u2, tr_u1). As a correction signal superimposed on the command signal, the first correction signal (for U phase) that converges the DC component included in the average value of the exciting currents of the U-phase transformers 21 and 22 (tr_u2, tr_u1) to zero. Has a control element that produces.

Similarly, the overall demagnetization 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 demagnetization of the V-phase transformers 23 and 24 (tr_v2, tr_v1). As a correction signal superimposed on the voltage command signal, the first correction signal (for V phase) that converges the DC component included in the average value of the exciting currents of the V-phase transformers 23 and 24 (tr_v2, tr_v1) to zero. ) Has a control element to generate.

Similarly, the overall demagnetization suppression control unit 62 sends 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 superimposed on the voltage command signal, the first correction signal (for W phase) that converges the DC component included in the average value of the exciting currents of the W phase transformers 25 and 26 (tr_w2, tr_w1) to zero. ) Has a control element to generate.

The individual demagnetization suppression control unit 63 is a U-phase based on the value of the exciting current of each transformer obtained from the current value detected by the current detectors 41 to 46 and the current value detected by the current detectors 51 to 53. DC eccentricity variation between transformers 21 and 22 (tr_u2, tr_u1), DC eccentricity variation between V-phase transformers 23 and 24 (tr_v2, tr_v1), and W-phase transformers 25 and 26. It is a function to perform control (individual demagnetization suppression control) to suppress the variation of DC demagnetization between (tr_w2, tr_w1). The individual demagnetization suppression control unit 63 does not use the signal that has passed through the filter that causes a waste time in control for control, and uses only the signal that does not pass through the filter for control.

For example, the individual demagnetization suppression control unit 63 further suppresses the variation in DC demagnetization between the U-phase transformers 21 and 22 (tr_u2, tr_u1) with respect to the first correction signal (for U-phase). As the superimposed correction signal, a second correction signal (for U phase) that converges the exciting currents of the U-phase transformers 21 and 22 (tr_u2, tr_u1) to the average value of the respective exciting currents is used. It includes two control elements generated for each exciting current.

Similarly, the individual demagnetization suppression control unit 63 suppresses the variation in DC demagnetization between the V-phase transformers 23 and 24 (tr_v2, tr_v1) with respect to the first correction signal (for V-phase). Further, as a correction signal to be superimposed, a second correction signal (for V phase) that converges the exciting currents of the V-phase transformers 23 and 24 (tr_v2, tr_v1) to the average value of the respective exciting currents is used. Includes two control elements generated for each exciting current of.

Similarly, the individual demagnetization suppression control unit 63 refers to the first correction signal (for W phase) in order to suppress the variation in DC demagnetization between the W-phase transformers 25 and 26 (tr_w2, tr_w1). Further, as a correction signal to be superimposed, a second correction signal (for W phase) that converges the exciting currents of the W-phase transformers 25 and 26 (tr_w2, tr_w1) to the average value of the respective exciting currents is used. Includes two control elements generated for each exciting current of.

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, and obtains the converter output. This is a function to transmit 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 showing an example of a configuration for realizing DC 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 shown.

The control device 1 includes, for example, a subtraction unit 71, 72, an addition unit 73, a multiplication unit 74, a low-pass filter 75, a proportional integration control unit 76, a subtraction unit 81, 91, a proportional integration control unit 82, 92, and a subtraction unit 83, 93. , Subtraction units 84, 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 the exciting current (U-phase one-stage exciting current) value i_m_u1 of the transformer tr_u1. Similarly, the subtracting unit 72 subtracts the primary current value i_u from the secondary current value i_u2 of the transformer tr_u2 to calculate the exciting current (U-phase two-stage exciting current) value i_m_u2 of the transformer tr_u2.

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

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

The filter 75 extracts the exciting current DC component (U-phase exciting 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 exciting current output from the adder 73. A general low-pass filter (a filter that passes a signal having a frequency lower than a certain frequency) may be applied to the filter 75, but 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 cycle) may be replaced with a moving average filter that sequentially outputs the moving average.

The proportional integration control unit 76 constitutes at least a part of the overall demagnetization suppression control unit 62 described above. The proportional integration control unit 76 is a control element that realizes overall demagnetization suppression control, and performs, for example, a proportional integration operation PI in order to converge the U-phase exciting current DC component i_m_u_dc to zero, and is used for a U-phase converter. U-phase converter output voltage command value (reference value) U-phase demagnetization suppression correction voltage command value vref_m_u (corresponding to the above-mentioned first correction signal (for U phase)) is generated as a correction value for vref_u. The proportional integration gain used in the proportional integration 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 form a part of the individual demagnetization suppression control unit 63 described above. Similarly, the subtraction unit 91, the proportional integration control unit 92, the subtraction unit 93, and the subtraction unit 94 also form a part of the individual demagnetization suppression control unit 63 described above.

The subtracting unit 81 subtracts the U-phase one-stage exciting current value i_m_u1 calculated by the subtracting unit 71 from the U-phase exciting current value i_m_u calculated by the multiplying unit 74, and U-phase exciting current values i_m_u and U. The difference from the value i_m_u1 of the phase 1-stage exciting current is output.

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

The subtraction 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, and directs the U-phase one-stage converter cnv_u1. Generates the converter output voltage command value vref_u1 of.

Similarly, the subtracting unit 91 subtracts the U-phase two-stage exciting current i_m_u2 calculated by the subtracting unit 72 from the U-phase exciting current value i_m_u calculated by the multiplying unit 74, and sets the U-phase exciting current value i_m_u. The difference from the U-phase two-stage exciting current value i_m_u2 is output.

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

The subtraction 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. Generates the converter output voltage command value vref_u2.

The proportional integration control units 82 and 92 described above do not use the signal that has passed through the low-pass filter or the like that causes a waste time in control for control. Therefore, the proportional integration 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, it is unlikely that the control response vibrates and becomes unstable. By setting the respective control gains of the proportional integration control units 82 and 92 to be larger than the control gain of the proportional integration control unit 76, for example, the control response can be accelerated and the exciting current between the U-phase transformers can be increased. It is possible to suppress the variation even more accurately.

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

During the operation of the multiplex power converter configured in this way, the individual current values detected by the current detectors 41 to 46 and the current detectors 51 to 53 shown in FIG. 1 are continuously transferred to the control device 1. Be transmitted. In the control device 1, transformers 21 to 26 (tr_u2, tr_u1, tr_v2, tr_v1, tr_w2, tr_w1) are based on the individual current values detected by these current detectors 41 to 46 and current detectors 51 to 53. It is supplied to converters 11 to 16 (cnv_u2, cnv_u1, cnv_v2, cnv_v1, cnv_w2, cnv_w1) so that the DC demagnetization that may occur in the above is suppressed and the variation in the exciting current between the transformers of each phase is suppressed. The converter output voltage command values Vref_u1, Vref_u2, Vref_v1, Vref_v2, Vref_w1, Vref_w2 are adjusted.

For example, for the U phase, as shown in FIG. 3, in the subtraction unit 71, the primary current value i_u is subtracted from the secondary current value i_u1 of the transformer tr_u1 to calculate the U phase 1-stage exciting current value i_m_u1. Will be done. Similarly, in the subtraction unit 72, the value i_u of the primary current is subtracted from the value i_u2 of the secondary current of the transformer tr_u2, and the value i_m_u2 of the U-phase two-stage exciting current is calculated.

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 exciting current (U-phase one-stage exciting current) value i_m_u1 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 exciting current (U-phase two-stage exciting current) value i_m_u2 of the transformer tr_u2.

Next, in the addition unit 73, 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 are added, and the addition result is output. Further, in the multiplication unit 74, 0.5 is multiplied by the addition result, and the value i_m_u of the U-phase exciting current is output. That is, here, the average value of the exciting currents of the U-phase transformers tr_u1 and tr_u2 is calculated.

Here, the relationship between the U-phase one-stage exciting current value i_m_u1, the U-phase two-stage exciting current value i_m_u2, and the U-phase two-stage exciting current value i_m_u 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 U-phase 1-stage exciting current value i_m_u1 and the U-phase 2-stage exciting current value i_m_u2 corresponds to the U-phase exciting current value i_m_u.

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

On the other hand, in the subtraction unit 81, the value i_m_u1 of the U-phase one-stage exciting current calculated by the subtraction unit 71 is subtracted from the value i_m_u of the U-phase exciting current calculated by the multiplication unit 74, and the value of the U-phase exciting current. The difference between i_m_u and the U-phase one-stage exciting current value i_m_u1 is output. Further, in the proportional integration control unit 82, for example, the proportional integration operation PI1 is executed in order to converge the difference to zero, and a correction value for the above-mentioned U-phase demagnetization suppression correction voltage command value vref_m_u is generated. Further, in the subtraction unit 83, this generated correction value is subtracted from the U-phase demagnetization suppression correction voltage command value vref_m_u, and the correction value for the U-phase converter output voltage command value (reference value) ref_u (U-phase one-step deviation). Magnetic suppression correction voltage command value) vref_m_u1 is generated.

Similarly, in the subtraction unit 91, the U-phase two-stage exciting current i_m_u2 calculated by the subtraction unit 72 is subtracted from the U-phase exciting current value i_m_u calculated by the multiplication unit 74, and the U-phase exciting current value i_m_u The difference between and the U-phase two-stage exciting current value i_m_u2 is output. Further, in the proportional integration control unit 92, for example, the proportional integration calculation PI2 is performed in order to converge the difference to zero, and a correction value for the above-mentioned U-phase demagnetization suppression correction voltage command value vref_m_u is generated. Further, in the subtraction unit 93, this generated correction value is subtracted from the U-phase demagnetization suppression correction voltage command value vref_m_u, and the correction value for the U-phase converter output voltage command value (reference value) vref_u (U-phase two-stage bias). Magnetic suppression correction voltage command value) vref_m_u2 is generated.

Here, the relationship between the U-phase one-stage demagnetization suppression correction voltage command value vref_m_u1 and the U-phase two-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, the U-phase 1-stage demagnetization suppression correction voltage command value vref_m_u1 for the U-phase 1-stage converter cnv_u1 and the U-phase 2-stage demagnetization suppression correction voltage command value vref_m_u2 for the U-phase converter cnv_u2. However, it can be seen that the values are different from each other and are individually generated for each converter.

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

Here, the U-phase converter output voltage command value (reference value) vref_u, 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. The relationship between the above 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 the U-phase converter output voltage command values ( Reference value) It can be seen that the values are different for vref_u and are individually generated for each converter.

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

As a result, the converters 11 and 12 (cnv_u2, cnv_u1) generate output voltages according to the converter output voltage command values vref_u1 and vref_u2, respectively. Since the converter output voltage command values vref_u1 and vref_u2 suppress the variation in the output voltage between the converters 11 and 12 (cnv_u2, cnv_u1), the variation in the exciting current between the transformers is also suppressed.

The operation of the V phase and the W phase is the same as that of the U phase described above.

As described above, according to the present embodiment, it is possible to suppress the variation in the DC demagnetization between the transformers in each phase of the three-phase AC by implementing the individual demagnetization suppression control in addition to the overall demagnetization suppression control. It is possible to avoid magnetic saturation of each transformer.

Further, in the individual demagnetization suppression control of the present embodiment, the signal that has passed through the filter that causes a waste time in control is not used for the control. For example, the individual control elements that perform individual demagnetization suppression control for each phase of three-phase alternating current do not use the signal that has passed through a low-pass filter or the like that causes a waste time in control for control. Therefore, the individual control elements that perform the individual demagnetization suppression control do not have 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. The possibility is low, and by setting the control gain of each of the control elements to be larger than the control gain of the control element that performs overall demagnetization suppression control, for example, the control response is made faster, which is caused by switching, etc. It is possible to suppress the variation of the exciting current between the transformers with higher accuracy.

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

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Control device, 10 ... DC power supply, 11-16 ... Converter, 21-26 ... Transformer, 31-33 ... Load, 41-46, 51-53 ... Current detector, 61 ... Signal receiver, 62 ... Overall Demagnetization suppression control unit, 63 ... Individual demagnetization suppression control unit, 64 ... Signal transmission unit.

Claims (6)

A control device for a power converter that converts DC power into AC power through multiple converters and multiple transformers.
Control to generate a first correction signal that converges the DC component included in the average value of the excitation currents of the plurality of transformers to zero as the correction signal superimposed on the converter output voltage command signal sent to the plurality of converters. Overall demagnetization suppression control unit including elements,
As a correction signal further superimposed on the first correction signal, a plurality of control elements that generate a second correction signal that converges the exciting currents of the plurality of transformers to the average value of the respective exciting currents. Individual demagnetization suppression control unit including
Equipped with
The individual demagnetization suppression control unit uses only signals that do not pass through the filter, excluding the signals that have passed through the filter that causes a waste time in control, for control.
A control device for a power converter. Each of the plurality of control elements included in the individual demagnetization suppression control unit is set to have a larger control gain than the control elements included in the overall demagnetization suppression control unit.
The control device for the power conversion device according to 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 device for the power conversion device according to claim 1 or 2. The overall demagnetization suppression control unit
By using a low-pass filter, a DC component is extracted from the average value of the exciting currents of each of the plurality of transformers.
The control device for the power conversion device according to any one of claims 1 to 3. The overall demagnetization suppression control unit
By using a moving average filter, a DC component is extracted from the average value of the exciting currents of each of the plurality of transformers.
The control device for the power conversion device according to any one of claims 1 to 4. A control method for a power converter that converts DC power into AC power through multiple converters and multiple transformers.
The first control unit converges the DC component included in the average value of the exciting currents of the plurality of transformers to zero as a correction signal superimposed on the converter output voltage command signals sent to the plurality of converters. To 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 that converges the exciting currents of the plurality of transformers to the average value of the respective exciting currents. To generate and
Including
In the generation of the second correction signal by the second control unit, only the signal that does not pass through the filter except for the signal that has passed through the filter that causes the control dead time is used for control.
How to control the power converter.

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