JP2008141804A - Serial multiple AC / DC converter and control method - Google Patents

Abstract

An object of the present invention is to continue operation and obtain a desired capacity even when any converter of a serial multiple converter is stopped due to a failure.
A serial multiple converter 11 is formed by combining a plurality of power converters 12 having the same or different rated capacities and connecting them in series to each of three phases. The device 18 includes a converter 12 connected to each of the three phases of the serial multiple converter 11 such that the output line voltage of each of the three phases of the serial multiple converter 11 maintains a balanced three-phase line voltage. Adjust and control the phase or magnitude of the output voltage.
[Selection] Figure 1

Description

  The present invention relates to a serial multiple AC / DC converter and a control method including a serial multiple converter in which a plurality of power converters are connected in series to three phases.

  For example, as a power converter that converts direct current into alternating current, there is one in which a plurality of converters are connected in series for each of the three phases to form a serial multiple converter. Usually, the converters connected in series to each of the three phases have the same rated capacity, and the output voltage of the converter of each phase is the same during normal operation.

  When a failure or the like occurs in any converter of such a serial multiple converter, the serial multiple converter is immediately stopped and the failed converter is replaced with a healthy converter. This replacement work requires on-site replacement work to a healthy converter, a confirmation test, and the like, and usually takes more than half a day, so the power converter is stopped during that time.

  In a large-capacity serial multiple converter for power use, the converter constituting the serial multiple converter is inspected for each arm or each phase, so the system may be stopped for several days. In particular, since there is a desire to reduce the recovery time in the event of a failure as much as possible, if it is not possible to stop the serial multiple converter continuously over such a long period of time, allow time for each arm unit or each phase unit. The current situation is that inspections are carried out sequentially.

  In addition, for industrial serial multiple converters and serial multiple converters for distributed power supplies, the serial multiple converter is stopped during inspection, or power is supplied by a bypass circuit when the serial multiple converter is stopped. However, when power is supplied by a bypass circuit, power is supplied from a commercial power source, and the original merit of the serial multiple converter cannot be maintained.

Here, in a system in which the DC side of multiple power converters is connected to provide power interchange, even if one power converter stops due to a grid fault or converter failure, the remaining healthy power There is one in which operation can be continued with a converter (see Patent Document 1).
Japanese Patent Laid-Open No. 9-74769

  However, in the thing of patent document 1, it is necessary to provide a spare power converter. As a countermeasure at the time of failure or inspection of a serial multiple converter configured by connecting a plurality of converters in series, a spare converter (for example, one phase) may be prepared. For example, it may be possible to switch to a spare converter at the time of failure or inspection of the converter constituting the serial multiple converter and continue the operation, but this reduces the operating rate per unit and converter The system capacity for one unit will increase, and the installation space will be limited.

  Furthermore, since the converters connected in series to each of the three-phase phases have the same rated capacity, it may not be possible to configure a serial multiple converter having a desired capacity. For example, when the rated capacity of a single converter is 50 kVA, the rated capacity for three phases is 150 kVA when using one converter for each phase, and 300 kVA when using two converters for each phase. Become. Similarly, when the rated capacity of a single converter is 200 kVA, the rated capacity for three phases is 600 kVA when using one converter for each phase, and 1200 kVA when using two converters for each phase. It becomes. That is, it is desired to produce a rated capacity that is a multiple of 3 times the rated capacity of a single converter because of standardization and rationalization of the design. To obtain an output that is not a multiple of 3 of the rated capacity of a single converter, a partial load I will drive.

  FIG. 13 shows a part in which the output voltage of the serial multiple converter is lowered when the number of three-phase converters of the serial multiple converter is two and the rated capacity of each converter is the same. It is an output voltage vector figure in the case of carrying out load operation.

  FIG. 13 (a) is an output voltage vector diagram during normal operation, and FIG. 3 (b) is a diagram showing the three-phase each phase by adjusting and controlling the magnitude of the output voltage of the converter while keeping the number of converters in operation constant. The output voltage vector diagram when the output line voltage is lowered, FIG. 13C shows the output line voltage of each of the three-phase converters of the three-phase converter by reducing the number of operating three-phase converters to one. It is an output voltage vector figure at the time of lowering.

  In FIG. 13A, during normal operation, the output voltages U1, U2 of the U-phase converter of the serial multiple converter 11, the output voltages V1, V2, of the V-phase converter, and the outputs of the W-phase converter. The voltages W1 and W2 have the same magnitude, and the U-phase, V-phase, and W-phase converter output voltages of the serial multiple converter 11 maintain a three-phase balanced current having a phase difference of 120 °. ing. In FIG. 13B, the output voltage of the U-phase converter of the serial multiple converter 11 is u1, u2, the output voltage of the V-phase converter is v1, v2, and the output voltage of the W-phase converter is w1. , W2 shows the case where the output line voltage of each phase of the three phases is lowered. In FIG. 13C, one of the U, V and W phase converters of the serial multiple converter 11 is stopped. In this case, the output voltages U1, V1, and W1 are set, and the output line voltage of each phase of the three phases is reduced.

  In other words, in the prior art, as shown in FIG. 3 (b), the output voltage of the three-phase each phase converter is lowered to perform partial load operation, or the number of operating three-phase each phase converter is reduced. A partial load operation was performed.

  When the output voltage of the three-phase converter is lowered and the converter is operated at a partial load, there is a problem that the efficiency of the converter is reduced. There was a problem that only partial load operation of change was possible.

Therefore, there has been a demand for a converter in which the efficiency does not decrease even when the load change is a continuous partial load. For example, in a converter applied to wind power generation, solar power generation, etc., the frequency of continuous partial load operation is high. For this reason, if efficient power generation can be continued even if the output fluctuates, renewable energy will be used effectively, leading to a reduction in CO ₂ emissions. As a result, it can be expected to prevent global warming.

  An object of the present invention is to provide a serial multiple AC / DC converter capable of continuing operation even when any converter of a serial multiple converter has stopped due to failure, and capable of operating without lowering efficiency even when the output fluctuates, and It is to provide a control method.

  The serial multiple AC / DC converter according to the invention of claim 1 is formed by combining a plurality of power converters including ones having the same or different rated capacities and connecting them in series to each of the three phases. A serial multiple converter and a converter connected to each of the three phases of the serial multiple converter so that the output line voltage of the three phases of the serial multiple converter maintains a balanced three-phase line voltage. And a converter control device that adjusts and controls the phase or magnitude of the output voltage.

  The serial multiple AC / DC converter according to the invention of claim 2 is characterized in that, in the invention of claim 1, the same number of converters are connected in series for each of the three phases.

  The serial multiple AC / DC converter according to the invention of claim 3 is characterized in that, in the invention of claim 1, the converter is characterized in that at least any one of the three-phase phases is connected in series. .

  The serial multiple type AC / DC converter according to the invention of claim 4 is the invention according to any one of claims 1 to 3, wherein the converter control device changes the number of converters to be operated. The phase or magnitude of the output voltage of the serial multiple converter is adjusted and controlled, and the output line voltage of each of the three phases maintains a balanced three-phase line voltage.

  The serial multiple type AC / DC converter according to the invention of claim 5 is the invention according to any one of claims 1 to 3, wherein the converter controller controls the number of operating converters of each of the three phases to be constant. As described above, the phase or magnitude of the output voltage of the converter is adjusted and controlled so that the output line voltage of each of the three phases of the serial multiple converter becomes a balanced three-phase line voltage.

  The serial multiple AC / DC converter according to the invention of claim 6 is the invention according to any one of claims 1 to 5, wherein the number of operating three-phase converters or the phase or magnitude of the output voltage of the converter. And the balanced three-phase line voltage is maintained at the same value as before the change.

  The serial multiple type AC / DC converter according to the invention of claim 7 is the invention according to any one of claims 1 to 6, wherein the converter controller is configured to calculate the number of operating units of each of the three phases or the output voltage of the converter. It is characterized in that the phase or size is adjusted and controlled to suppress fluctuations in the efficiency of the converter as much as possible. A serial multiplex type AC / DC converter according to the invention of claim 8 includes a serial multiplex converter in which a plurality of power converters are connected in series to three phases, respectively, and a converter of any of the serial multiplex converters. When the fault detector detects that the fault has stopped, and when the fault detector detects a faulty converter, the output line voltage of each of the three phases of the serial multiple converter holds the voltage when healthy. And a converter control device that adjusts and controls the phase or the magnitude of the output voltage of a healthy converter excluding the converter that has failed and stopped.

  The serial multiplexing type AC / DC converter according to the invention of claim 9 is the invention according to claim 8, wherein the converter controller controls the magnitude of the output voltage of each of the healthy converters excluding the converter that has failed. It is the same, and the phase of the phase to which the faulty converter is connected is the same as that at the time of soundness.

  The control method of the serial multiplex type AC / DC converter according to the invention of claim 10 is a three-phase AC in which a plurality of power converters having the same rated capacity and different ones are connected in series to each of the three-phase phases. In the control method of the serial multiple AC / DC converter for supplying power, the phase or magnitude of the output voltage of the converter connected to each of the three phases of the serial multiple converter is adjusted and controlled, and the serial multiple converter The output line voltage of each of the three phases is maintained at a balanced three-phase line voltage.

  A control method for a serial multiplex AC / DC converter according to the invention of claim 11 is a control method for a serial multiplex AC / DC converter in which a plurality of power converters are connected in series to each of the three phases to supply three-phase AC power. In the method, it is determined whether or not a failure of any converter of the serial multiple converter has stopped, and when none of the converters has failed, an output of each of the three phases of the serial multiple converter Control each converter of the serial multiplex converter so that the line voltage becomes a predetermined voltage, and when one of the converters is out of order, between the output lines of the three-phase each phase of the serial multiplex converter A control method for a serial multiplex AC / DC converter comprising adjusting and controlling the phase or magnitude of the output voltage of a healthy converter excluding the converter that has failed and stopped so that the predetermined voltage is maintained when the voltage is healthy .

  The control method of the serial multiple AC / DC converter according to the invention of claim 12 is the method of controlling the serial multiple AC / DC converter according to the invention of claim 11, when any one of the converters has failed. When adjusting and controlling the phase or magnitude of the output voltage of a healthy converter excluding the converter that has failed and stopped so that the voltage between the voltages is healthy, the magnitude of each output voltage of the healthy converter It is characterized in that the phase of the phase to which the converter that has failed and stopped is connected is the same as that in the normal state.

  According to the present invention, converters having the same or different rated capacities are connected to three-phase respective phases to form a serial multiple converter, and the output line voltage of each of the three phases of the serial multiple converter is a balanced three-phase line. Since the phase or magnitude of the output voltage of the converter connected to each phase of the three phases is adjusted and controlled so as to maintain the inter-voltage, a serial multiple converter that can be operated without lowering the efficiency even if the output fluctuates Can be configured.

  Also, even if one converter of the serial multiple converter is stopped due to failure, it is shared and operated by other healthy converters, so the output voltage of the serial multiple converter can be increased without providing a spare converter. It can be maintained at a healthy voltage. Further, it is not necessary to install a spare converter, and the installation space can be reduced. Furthermore, since the inspection can be performed without stopping the serial multiple converter, the reliability is improved, and the preventive maintenance of the equipment and the system failure rate can be reduced.

  FIG. 1 is a configuration diagram of a serial multiplex AC / DC converter according to the first embodiment of the present invention. The serial multiple converter 11 is provided with a plurality of converters 12 for each of the three phases. As for the number of converters 12 connected in series with respect to each of the three-phase phases, the same number or at least one of the three-phase each phase is differently connected in series. FIG. 1 shows a case where two converters 12 of the same number are provided for the U phase, V phase, and W phase of each of the three phases. That is, converters 12U1 and 12U2 are provided in the U phase, converters 12V1 and 12V2 are provided in the V phase, and converters 12W1 and 12W2 are provided in the W phase. Further, converters 12U1 to 12W2 are connected in combination with the same or different rated capacities.

  FIG. 2 is a circuit configuration diagram showing an example of one converter 12. The converter 12 is configured by connecting, for example, four IGBT (Insulated Gate Bipolar Transistor) modules 13, which are insulated gate semiconductor elements, in series and parallel, and converts DC power from the DC power supply 14 into AC power for winding. It outputs to the line 15.

  Then, as shown in FIG. 1, the winding 15 of the converter 12 is magnetically coupled to the primary winding of the transformer 16, and two coils are arranged in series in each of the three phases. Thereby, the output voltage of the two converters 12 connected in series is output from each primary winding of the transformer 16 for each phase.

  The converter control device 18 controls each of the converters 12U1 to 12W2, and changes the number of operating converters 12U1 to 12W2 of each of the three phases to be constant or changed so that each of the three phases of the serial multiple converter 11 is changed. The voltage command values and phase command values of the converters 12U1 to 12W2 are calculated so that the phase output line voltages U, V, and W become balanced three-phase line voltages. The voltage command value and phase command value of the converters 12U1 to 12W2 calculated by the converter control device 18 are input to the gate control circuit 23, and the gate control circuit 23 receives the voltage command value and phase command from the converter control device 18. A gate signal is output to the converters 12U1 to 12W2 so as to satisfy the value.

  As a result, the output voltages and phases of the three-phase converters 12U1 to 12W2 become unbalanced, but the three-phase output-phase voltages U, V, and W of the serial multiple converter 11 are balanced three-phase wires. Voltage.

  FIG. 3 shows a case where the output voltage of the serial multiple converter 11 is lowered when the number of converters in each of the three phases of the serial multiple converter 11 in the first embodiment of the present invention is the same and the rated capacity is the same. It is an output voltage vector figure which shows the Example of. 3A is an output voltage vector diagram during normal operation, and FIG. 3B is a diagram showing a decrease in the output line voltage of each of the three phases of the serial multiple converter 11 while the number of converters 12 is kept constant. FIG. 3 (c) shows the output voltage vector diagram when the magnitude of the output voltage of the converter is adjusted and controlled so as to maintain the balanced three-phase line voltage while FIG. It is an output voltage vector diagram at the time of adjusting and controlling the output voltage and phase of the converter so as to maintain the balanced three-phase line voltage while lowering the output line voltage of each of the three phases of the multiple converter 11.

  As shown in FIG. 3A, during normal operation, the U-phase converters 12U1 and 12U2 of the serial multiple converter 11 output voltages U1 and U2, the V-phase converters 12V1 and 12V2, and the output voltages V1 and 12V2, respectively. The output voltages W1 and W2 of the V2 and W phase converters 12W1 and 12W2 have the same magnitude, and the phase voltages of the U-phase, V-phase, and W-phase of the serial multiple converter 11 are about 120 °. A three-phase balanced voltage with phase difference is maintained. Moreover, the line voltages U, V, and W of the U-V phase, the V-W phase, and the W-U phase, which are the output line voltages of the three phases of the serial multiple converter 11, each have a phase difference of 120 °. Maintains a three-phase balanced voltage.

  In this state, when the number of converters 12U1 to W2 of the serial multiple converter 11 is kept constant, the magnitudes of the output line voltages U, V, and W of the three-phase each phase of the serial multiple converter 11 are reduced. think of. FIG. 3B shows the three-phase of the serial multiple converter 11 by adjusting the magnitude of the output voltage of any one of the converters 12 in each of the three phases of the serial multiple converter 11. The case where the magnitude | size of the output line voltage U, V, and W of each phase is shown is shown. That is, the output voltage of the converter 12U2 is changed from U2 to u2 for the U phase of the serial multiple converter 11, the output voltage of the converter 12V2 is changed from V2 to v2 for the V phase, and the output voltage of the converter 12W2 is set for the W phase. Is changed from W2 to w2, the magnitudes of the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11 are changed.

  On the other hand, FIG. 3C adjusts the magnitude of the output voltage of the converter 12 of any one of the three phases of the serial multiple converter 11 and the magnitude of the output voltage of the converter 12 of the two phases. The figure shows the case where the magnitude of the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11 is changed by adjusting the phase while keeping the constant. That is, the output voltage of the converters 12W1 and 12W2 is lowered for the W phase of the serial multiple converter 11, and the output voltages of the converters 12U1 (12V1) and 12U2 (12V2) are constant for the U phase and the V phase. The phases of the U phase and the V phase are changed so that the output line voltages U, V, and W of the three phases of the converter 11 maintain the three-phase balanced voltage.

  In this case, as shown in FIG. 3C, the output voltage and phase of each of the three phases of the serial multiple converter 11 are unbalanced, but the output lines of the three phases of the serial multiple converter 11 are not balanced. The inter-voltages U, V, and W are balanced three-phase line voltages. Thus, as long as the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11 become balanced three-phase line voltages, the output voltage of the three-phase each phase of the serial multiple converter 11 The operation in which the phases are unbalanced is allowed, and the output line voltages U, V, and W of the three phases of the serial multiple converter 11 can be changed. Thus, a serial multiple converter having a desired capacity can be configured.

  FIG. 4 shows an example of the output voltage of the serial multiple converter 11 when the number of three-phase converters of the serial multiple converter 11 in the first embodiment of the present invention is the same and the rated capacity is different. It is an output voltage vector diagram. 4 (a) is an output voltage vector diagram during normal operation, and FIGS. 4 (b) and 4 (c) are three-phase output lines of the serial multiple converter 11 by changing the number of converters 12 operated. It is an output voltage vector figure at the time of carrying out adjustment control of the magnitude | size of the output voltage of a converter so that a balanced three-phase line voltage may be maintained, reducing an inter-voltage.

  As shown in FIG. 4A, the number of converters 12 for each of the three phases is the same for each two, but the rated capacity of the two converters for the W phase is the conversion between the U phase and the V phase. What is half the rated capacity of the vessel is used. Therefore, during normal operation, the output voltages U1 and U2 of the U-phase converters 12U1 and 12U2 of the serial multiple converter 11 and the output voltages V1 and V2 of the V-phase converters 12V1 and 12V2 are the same. The output voltages W1, W2 of the W-phase converters 12W1, 12W2 are ½ of the output voltages of the U-phase and V-phase converters. For this reason, the output voltage and phase of each of the three phases of the serial multiple converter 11 are unbalanced.

  In addition, although the output voltage and phase of each of the three phases of the serial multiple converter 11 are unbalanced, the output line voltages U, V, and W of each of the three phases of the serial multiple converter 11 are between the balanced three phase lines. It is adjusted to be a voltage. Therefore, the line voltages U, V, and W of the U-V phase, the V-W phase, and the W-U phase, which are the output line voltages of the three phases of the serial multiple converter 11, each have a phase difference of 120 °. Maintains a three-phase balanced voltage. Thus, even during normal operation, as long as the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11 become balanced three-phase line voltages, the three-phase of the serial multiple converter 11 Operation in which the output voltage and phase of each phase are unbalanced is allowed.

  In this state, the operation number of converters 12U1 to W2 of the serial multiple converter 11 is changed to reduce the magnitudes of the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11. Think. FIG. 4B shows the magnitudes of the U-phase and V-phase output voltages of the serial multiple converter 11 when the U-phase and V-phase converters U2 and V2 of the serial multiple converter 11 are stopped or the output voltage is set to zero. The case where the magnitudes of the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11 are changed after adjustment is shown. That is, the output voltage of the converters 12W1 and 12W2 is left as it is for the W phase of the serial multiple converter 11, and the output voltage of the converter 12U2 (12V2) is 0 for the U phase and the V phase. The phases of the U phase and the V phase are changed so that the output line voltages U, V, and W of the three phases of the device 11 maintain the three-phase balanced voltage. Thereby, the magnitude | size of the output line voltage U, V, W of the three-phase each phase of the serial multiple converter 11 can be lowered | hung.

  FIG. 4 (c) shows that the W-phase converter W2 of the serial multiple converter 11 is stopped or the output voltage is set to 0, and the magnitude of the W-phase output voltage of the serial multiple converter 11 is adjusted. 11 shows a case where the magnitudes of the output line voltages U, V, and W of the three three-phase phases are changed. That is, for the U phase and V phase of the serial multiple converter 11, the output voltages of the converters 12U1, 12U2, and converters 12V1, 12V2 are left as they are, and for the W phase of the serial multiple converter 11, the output voltage of the converter 12W2 is The phase of the U phase and the V phase is changed so that the output line voltages U, V, and W of the three phases of the serial multiple converter 11 maintain a three-phase balanced voltage. Thereby, the magnitude | size of the output line voltage U, V, W of the three-phase each phase of the serial multiple converter 11 can be lowered | hung. In the above description, the case where the same number of converters 12 are connected in series to each of the three-phase phases has been described, but at least one of the three-phase phases is connected in series with a different number of converters 12. The same applies to the case.

  FIG. 5 shows the implementation of the output voltage of the serial multiple converter 11 when the number of three-phase converters of the serial multiple converter 11 in the first embodiment of the present invention is different and the rated capacity of each converter is also different. It is an output voltage vector diagram which shows an example. FIG. 5 (a) shows the output voltage vector diagram during normal operation, and FIG. 5 (b) shows the output line voltage of each of the three phases of the serial multiple converter 11 being lowered while the number of converters 12 operated is kept constant. FIG. 5 (c) shows the output voltage vector diagram when the magnitude of the output voltage of the converter is adjusted and controlled so as to maintain the balanced three-phase line voltage while FIG. It is an output voltage vector diagram at the time of adjusting and controlling the output voltage and phase of the converter so as to maintain the balanced three-phase line voltage while lowering the output line voltage of each of the three phases of the multiple converter 11.

  As shown in FIG. 5A, the number of converters 12 for each of the three phases is different, and three converters 12U1, U2, U3 (12V1, V2, V3) are connected to the U phase and the V phase. In the W phase, two converters 12W1 and 12W2 are connected. The rated capacities of the two W-phase converters 12W1 and 12W2 are the same as the rated capacities of the U-phase converter 12U3 and the V-phase converter 12V3, and the U-phase converters 12U1, 12U2 and the V-phase The rated capacities of the converters 12V1 and 12V2 are ½ of the rated capacities of the W-phase converters 12W1 and 12W2. During normal operation, the phase voltage of the U-phase, V-phase, and W-phase of the serial multiple converter 11 maintains a three-phase balanced voltage having a phase difference of 120 °. Moreover, the line voltages U, V, and W of the U-V phase, the V-W phase, and the W-U phase, which are the output line voltages of the three phases of the serial multiple converter 11, each have a phase difference of 120 °. Maintains a three-phase balanced voltage.

  In this state, the case where the magnitudes of the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11 are lowered while the number of the converters 12 of the serial multiple converter 11 is kept constant is considered. . FIG. 5B shows the three-phase of the serial multiple converter 11 by adjusting the magnitude of the output voltage of any one of the converters 12 of the three-phase converters 11 of the serial multiple converter 11. The case where the magnitude | size of the output line voltage U, V, and W of each phase is shown is shown. That is, for the U phase of the serial multiple converter 11, the output voltage of the converter 12U3 is changed from U3 to u3, for the V phase, the output voltage of the converter 12V3 is changed from V3 to v3, and for the W phase, the output voltage of the converter 12W2 Is changed from W2 to w2, the magnitudes of the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11 are changed.

  On the other hand, FIG. 5C shows the magnitude of the output voltage of the converter 12 of any one of the three phases of the serial multiple converter 11 and the magnitude of the output voltage of the converter 12 of the two phases. The figure shows the case where the magnitude of the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11 is changed by adjusting the phase while keeping the constant. That is, for the W phase of the serial multiple converter 11, the output voltages of the converters 12W1 and 12W2 are lowered, and for the U phase and the V phase, the output voltages of the converters 12U1 (12V1), 12U2 (12V2), and 12U3 (12V3) are The phase of the U phase and the V phase is changed so that the output line voltages U, V, and W of the three phases of the serial multiple converter 11 maintain a three-phase balanced voltage.

  FIG. 6 shows the output voltage of the serial multiple converter 11 when the number of three-phase converters of the serial multiple converter 11 in the first embodiment of the present invention is different and the rated capacity of each converter is also different. It is an output voltage vector figure which shows the Example of. 6 (a) is an output voltage vector diagram during normal operation, and FIGS. 6 (b) and 6 (c) are three-phase output lines of the serial multiple converter 11 by changing the number of converters 12 operated. It is an output voltage vector figure at the time of carrying out adjustment control of the magnitude | size of the output voltage of a converter so that a balanced three-phase line voltage may be maintained, reducing an inter-voltage.

  As shown in FIG. 6A, the number of converters 12 for each of the three phases is different, and three converters 12U1, U2, U3 (12V1, V2, V3) are connected to the U phase and the V phase. In the W phase, two converters 12W1 and 12W2 are connected. The rated capacities of the two W-phase converters 12W1 and 12W2 are the same as the rated capacities of the U-phase converters 12U1 and 12U2 and the V-phase converters 12V1 and 12V2, and the U-phase converter 12U3 and What is 1/2 of the rated capacity of the V-phase converter 12V3 is used.

  During normal operation, the phase voltage of the U-phase, V-phase, and W-phase of the serial multiple converter 11 is an unbalanced three-phase voltage, but is the output line voltage of each of the three phases of the serial multiple converter 11. Line voltages U, V, and W of a certain U-V phase, V-W phase, and W-U phase maintain a three-phase balanced voltage having a phase difference of 120 °. Thus, even during normal operation, as long as the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11 become balanced three-phase line voltages, the three-phase of the serial multiple converter 11 Operation in which the output voltage and phase of each phase are unbalanced is allowed.

  In this state, consider the case where the number of converters 12 in the serial multiple converter 11 is changed to reduce the magnitudes of the output line voltages U, V, and W of the three phases of the serial multiple converter 11. FIG. 6B shows the magnitudes of the U-phase and V-phase output voltages of the serial multiple converter 11 by stopping the U-phase and V-phase converters 12U3 and 12V3 of the serial multiple converter 11 or setting the output voltage to 0. The case where the magnitudes of the output line voltages U, V, W of the three-phase each phase of the serial multiple converter 11 are changed after adjustment is shown. That is, the output voltage of the converters 12W1 and 12W2 is left as it is for the W phase of the serial multiple converter 11, and the output voltage of the converter 12U3 (12V3) is 0 for the U phase and the V phase. The phases of the U phase and the V phase are changed so that the output line voltages U, V, and W of the three phases of the device 11 maintain the three-phase balanced voltage. Thereby, the magnitude | size of the output line voltage U, V, W of the three-phase each phase of the serial multiple converter 11 can be lowered | hung.

In FIG. 6C, the V-phase converter 12V3 of the serial multiple converter 11 is stopped or the output voltage is set to 0, and the magnitude of the V-phase output voltage of the serial multiple converter 11 is adjusted. The case where the magnitude | size of the output line voltage U, V, and W of each phase of three phases is changed is shown. That is, the output voltage of the converters 12 U 1, 12 U 2, 12 W 1, 12 W 2 is kept as it is for the U phase and the W phase of the serial multiple converter 11, and the output voltage of the converter 12 V 3 is 0 for the V phase, The phases of the V and W phases are changed so that the output line voltages U, V, and W of the three phases of the serial multiple converter 11 maintain the three-phase balanced voltage. Thereby, the magnitude | size of the output line voltage U, V, W of the three-phase each phase of the serial multiple converter 11 can be lowered | hung.

  In the above embodiments, the case where the magnitude of the line voltage of each phase is reduced has been described, but the rating and the number of phases can be changed without changing the output line voltage of each phase. The output can also be maintained.

  In addition, the phase and magnitude of the output voltage vector of the three-phase converter can be freely changed under the condition of maintaining the output line voltage in a balanced three-phase state. Furthermore, by freely changing the phase and magnitude of the output voltage vector of the three-phase phase converter, the phase and magnitude of the voltage / current vector of the output line voltage of the three-phase phase can be freely changed. You can also. As a result, a desired three-phase balanced or three-phase unbalanced output line voltage can be obtained while maintaining high efficiency operation.

  Next, the loss when the number of operating converters 12 of each phase is changed will be described. FIG. 7 shows the output line voltage (pu) and loss (%) of the serial multiple AC / DC converter 11 having four converters 12 for each phase and having a total of 12 converters 12. It is a graph which shows the relationship. The broken line L1 represents the characteristic in the case of the conventional method (the method of adjusting the output voltage by changing the modulation rate by selecting only a multiple of 3), and the broken line L2 represents the characteristic in the present invention. The numerical values at the break points in FIG. 7 indicate the number of operating converters.

Table 1 is a table showing the number of operating converters, output line voltage (pu), and loss (%) at each break point of the broken line L1 in the conventional method.

Table 2 is a table showing the number of operating converters, output line voltage (pu), and loss (%) at each break point of the broken line L2 in the method of the present invention.

  Now, when all four converters 12 of each phase are operated at a modulation rate (m = 1) (when 12 units are operated), the maximum voltage (output line voltage is 1.00 p.u.). It is assumed that the loss of the converter 12 of the serial multiple AC / DC converter 11 when the converter 12 is operated at a modulation rate (m = 1) is about 1.03%.

  Then, when the converters 12 of each phase are operated with the same number and the modulation rate (m = 1), the loss of the converter 12 of the serial multiplex AC / DC converter 11 is the present invention even in the conventional method. In both cases, it is the same at about 1.03%. That is, when one converter 12 for each phase (when three units are operated) is operated at a modulation rate (m = 1), two converters 12 for each phase (when six units are operated) When operating at a modulation rate (m = 1), when three converters 12 for each phase (when 9 units are operating) are operated at a modulation rate (m = 1), The loss of the converter 12 of the converter 11 is the same at about 1.03% in any case.

  Next, for example, when the output line voltage is set to 0.82 pu, in the conventional method, 4 units (12 units operation) of each phase are operated with the modulation rate reduced from 1 to 0.82, and the loss occurs. Increases to about 1.25%. On the other hand, the system of the present invention can be operated with a total number other than a multiple of 3, so that 4 units of U phase, 3 units of V phase and 3 units of W phase (10 units operation) are operated while keeping the modulation rate at 1. In this case, the loss is about 1.03% to 1.04% which hardly fluctuates. Thus, even if the number of operating three-phase phases or the phase or magnitude of the output voltage of the converter is changed, fluctuations in the efficiency of the converter can be suppressed as much as possible.

  According to the first embodiment of the present invention, the converter 12 having the same or different rated capacity is connected to each of the three-phase phases to form the serial multiple converter 11. The output voltage and phase of each of the three phases of the serial multiple converter 11 are allowed to be unbalanced and connected to each of the three phases so that the output line voltage maintains the balanced three-phase line voltage. Since the phase or magnitude of the output voltage of the converter 12 is adjusted and controlled, the serial multiple converter 11 can have a desired capacity without being restricted by the rated capacity of the converter 12. Moreover, it is also possible to replace a part of the output voltage with another healthy converter 12 with respect to the converter 12 whose rated capacity has decreased due to secular change or the like.

  Next, a second embodiment of the present invention will be described. FIG. 8 is a block diagram of a serial multiplex AC / DC converter according to the second embodiment of the present invention. In the second embodiment, a failure detector 17 is provided with respect to the first embodiment shown in FIG. 1, and the converter controller 12 detects the converter 12 in which the failure detector 17 has stopped. In this case, the phase or magnitude of the output voltage of the sound converter 12 except for the converter 12 that has failed is stopped so that the output line voltage of each of the three phases of the serial multiple converter maintains the sound voltage. The height is adjusted and controlled.

  In FIG. 8, the serial multiple converter 11 is provided with a plurality of converters 12 for each of the three phases. FIG. 8 shows a case where two converters 12 are provided for the U phase, V phase, and W phase of each of the three phases. That is, converters 12U1 and 12U2 are provided in the U phase, converters 12V1 and 12V2 are provided in the V phase, and converters 12W1 and 12W2 are provided in the W phase.

  Then, as shown in FIG. 8, the winding 15 of the converter 12 is magnetically coupled to the primary winding of the transformer 16, and two coils are arranged in series in each of the three phases. Thereby, the output voltage of the two converters 12 connected in series is output from each primary winding of the transformer 16 for each phase.

  Further, a failure detector 17 for detecting that any of the converters 12U1 to 12W2 of the serial multiple converter 11 has stopped is provided, and the converters 12U1 to 12W2 detected by the failure detector 17 are provided. The failure stop signal is input to the converter controller 18.

  The converter control device 18 controls each of the converters 12U1 to 12W2, and includes a normal time command value calculation means 19 and a failure stop time command value calculation means 20. The normal command value calculation means 19 calculates the voltage command value and the phase command value so that each of the converters 12U1 to 12W2 outputs a predetermined three-phase AC voltage. On the other hand, the failure stop command value calculation means 20 is started by the failure stop determination means 21, and the conversion that has failed and stopped so that the output line voltage of each of the three phases of the serial multiple converter 11 maintains the healthy voltage. The voltage command value and the phase command value of the healthy converter 12 excluding the converter 12 are calculated.

  Next, when the fault detector 17 detects the faulty converter 12, the fault stop judging means 21 identifies the faulty converter 12 and activates the fault stop command value calculating means 20. The switching means 22 is activated. The switching means 22 selects the output of the normal-time command value calculation means 19 and outputs it to the gate control circuit 23 under normal conditions. When the fault detector 17 detects the converter 12 that has failed and stopped, The output of the command value calculation means 20 at the time of stop is selected. The gate control circuit 23 outputs a gate signal to the converters 12U1 to 12W2 so that the voltage command value and the phase command value from the switching unit 22 are satisfied.

  Thereby, when each converter 12U1 to 12W2 of the serial multiple converter 11 is normal, each converter 12U1 to 12W2 is controlled by the voltage command value and the phase command value from the normal command value calculation means 19. On the other hand, when any one of the converters 12U1 to 12W2 of the serial multiple converter 11 is stopped due to a failure, the converters 12U1 to 12U1 are converted according to the voltage command value and the phase command value from the command value calculation means 20 at the time of failure stop. 12W2 is controlled.

  FIG. 9 is an output voltage vector diagram of the serial multiple converter 11 when any one converter 12 of the serial multiple converter 11 is out of order. FIG. 9A is an output voltage vector diagram when each of the converters 12U1 to 12W2 of the serial multiple converter 11 is normal, and FIG. 9B is a diagram showing that the converter 12W2 of the serial multiple converter 11 is stopped due to a failure. It is an output voltage vector figure at the time of sharing an output with the remaining healthy converters 12U1-12W1.

  As shown in FIG. 9A, when each of the converters 12U1 to 12W2 of the serial multiple converter 11 is normal, the output voltages U1, U2, and V phase of the U phase converters 12U1 and 12U2 are converted. The output voltages V1 and V2 of the converters 12V1 and 12V2 and the output voltages W1 and W2 of the W-phase converters 12W1 and 12W2 have the same magnitude, and the phase voltages of the U-phase, V-phase, and W-phase are 120 respectively. Maintains a three-phase balanced voltage with a phase difference of °. Further, the line voltages of the U-V phase, the V-W phase, and the W-U phase also maintain a three-phase balanced voltage having a phase difference of 120 °.

  In this state, assuming that the converter 12W2 of the serial multiple converter 11 is out of order, the output voltage of the W-phase converter 12W2 becomes zero. Therefore, the phase or magnitude of the output voltages U1 to W1 of the healthy converters 12U1 to 12W1 excluding the W-phase converter 12W2 that has failed is adjusted and controlled, and the output line voltage (U− The line voltage of the V phase, the V-W phase, and the W-U phase) is controlled so as to maintain the voltage when healthy.

  As shown in FIG. 9B, when the outputs are shared by the remaining healthy converters 12U1 to 12W1, the phase voltages of the U phase (u1 + u2), the V phase (v1 + v2), and the W phase (w1) are in an unbalanced state. However, the line voltages of the U-V phase, the V-W phase, and the W-U phase are three-phase balanced voltages. In FIG. 9B, the magnitudes of the output voltages u1 to w1 of the sound converters 12U1 to 12W1 are the same, and the phase of the W phase to which the converter 12W2 that has failed is connected is the same as that at the time of sound. Shows the case.

  FIG. 10 is an explanatory diagram regarding the adjustment control of the phase or size of the output voltages U1 to W1 of the healthy converters 12U1 to 12W1. Now, as shown in FIG. 10, each output voltage before sharing of the healthy converters 12U1 to 12W2 is U1 to W2, the neutral point of the phase voltage after sharing is O, and the sharing of the healthy converters 12U1 to 12W1 The subsequent output voltages are u1 to w1, and the output terminals of the three-phase output line voltages (U-V phase, V-W phase, W-U phase line voltages) are A, B, and C, respectively. To do. Then, U1 = U2 = V1 = V2 = W1 = 1, ∠AOB = 2θ, AB = BC = CA = a, u1 = u2 = v1 = v2 = w1 = b. Then, the following formula (1) is established.

sin θ = (a / 2) / 2b = a / 4b (1)
Further, the following equation (2) is established from the cosine theorem for ΔOCB.

a ² = b ² + (2b) ² -4b ² cos (π-θ)
cos θ = (a ² −5b ² ) / 4b ² (2)
Substituting Equations (1) and (2) into “sin ² θ + cos ² θ = 1” yields Equation (3).

a ² b ² + (a ² −5b ² ) ² = 16b ⁴
9b ⁴ -9a ² b ² + a ⁴ = 0 (3)
Here, since a = 2√3 and 0 <b <2√3 / 3, substituting a into equation (3) to obtain b yields equation (4).

b = √5-1 = 1.24 (4)
When θ = 2√3 and the equation (4) are substituted into the equation (1) to obtain θ, the equation (5) is obtained.

θ = ± 44.3 ° (5)
From the above, in order to share the output of the converter W1 that has failed in the sound converters 12U1 to 12W1, the magnitude of the output voltage of the sound converters 12U1 to 12W1 is increased 1.24 times, which is a failure phase. It is only necessary to shift the phases of the U phase and V phase other than the W phase to 44.3 °. In the above description, the case where there are two converters 12 for each phase has been described, but the same applies to the case where there are three converters 12 for each phase.

  FIG. 11 shows sound conversion when the W-phase converter 12W3 fails with three converters 12 for each phase (U-phase: 12U1 to 12U3, V-phase: 12V1 to 12V3, W-phase: 12W1 to 12W3). It is explanatory drawing about adjustment control of the phase or magnitude | size of the output voltages U1-W2 of the units 12U1-12W2.

  Now, as shown in FIG. 11, each output voltage before the sharing of the healthy converters 12U1 to 12W2 is U1 to W2, the neutral point of the phase voltage after the sharing is O, and the sharing of the healthy converters 12U1 to 12W2 The subsequent output voltages are u1 to w2, and the output terminals of the three-phase output line voltages (U-V phase, V-W phase, W-U phase line voltages) are A, B, and C, respectively. To do. And U1 = U2 = U3 = V1 = V2 = V3 = W1 = W2 = 1, ∠AOB = 2θ, AB = BC = CA = a, u1 = u2 = u3 = v1 = v2 = v3 = w1 = w2 = b And Then, the following equation (6) is established.

sin θ = (a / 2) / 3b = a / 6b (6)
Further, the following expression (7) is established from the cosine theorem for ΔOCB.

a ² = (2b) ² + (3b) ² −12b ² cos (π−θ)
cos θ = (a ² −13b ² ) / 12b ² (7)
Substituting Equations (6) and (7) into “sin ² θ + cos ² θ = 1” yields Equation (8).

^{25b 4 -22a 2 b 2 + a} 4 = 0 ... (8)
Here, since a = 3√3 and 0 <b <2√3 / 3, substituting a into equation (8) to obtain b yields equation (9).

b = 1.14 (9)
Further, when θ is obtained by substituting a = 3√3 and equation (9) into equation (6), equation (10) is obtained.

θ = ± 41.2 ° (10)
From the above, in order to share the output of the converter 12W3 that has failed in the sound converters 12U1 to 12W2, the magnitude of the output voltage of the sound converters 12U1 to 12W2 is 1.14 times, which is a failure phase. It is sufficient to shift the phase of the U phase and V phase other than the W phase to 41.2 °. The same applies when there are four or more converters 12 for each phase.

By increasing the number of multiplexed converters 12 for each phase, the voltage borne by the remaining healthy converters 12 when one converter 12 is stopped is reduced.

  Here, the magnitude of the output voltage of the healthy converter 12 may be adjusted by using the modulation rate, the voltage of the DC power supply 14 may be adjusted, or may be changed by tap switching on the AC side. It may be. Moreover, although the magnitude | size of each output voltage of the healthy converter 12 except the converter 12 which stopped by failure was made the same, the phase of the phase where the converter 12 which stopped by failure was connected was made into the same phase as the time of healthy. The output voltage of each of the healthy converters 12 can be secured, and the output line voltage (U-V phase, V-W phase, W-U phase line voltage) of each of the three phases is the voltage when healthy. As long as it can be ensured, the magnitude of the output voltage of each healthy converter 12 may be set to an arbitrary value within the range.

  FIG. 12 is a flowchart showing a control method of the serial multiple AC / DC converter according to the present invention. It is determined whether or not any of the converters 12 of the serial multiple converter 11 has failed and stopped (S1). If none of the converters 12 has stopped by failure, the voltage command value and the phase command at normal time are determined. The value is calculated (S2). And each converter 12 of the serial multiple converter 11 is controlled, and it controls so that the output voltage of the serial multiple converter 11 becomes a predetermined voltage (S3). On the other hand, when any of the converters 12 of the serial multiple converter 11 is stopped due to a failure, the failure is stopped so that the output line voltage of each phase of the three phases of the serial multiple converter 11 maintains a predetermined voltage when healthy. The voltage command value and phase command value of the output voltage of the healthy converter 12 excluding the converted converter 12 are calculated (S4). Then, the sound converter 12 except for the converter 12 that has failed is shared, and the sound converter 12 is controlled so that the output line voltage of each phase of the three phases maintains the predetermined voltage when healthy (S5). ).

  According to the second embodiment of the present invention, even if one converter 12 of the serial multiple converter 11 is in failure stop, the other healthy converters 12 share the output. The operation which maintained can be continued. Therefore, when applied to a DC power transmission system, reliability can be ensured without affecting the system due to power transmission stoppage. In addition, when applied to industrial inverters, it is possible to prevent manufacturing defects due to inverter shutdown, and when used in auxiliary equipment such as nuclear power plants, the generator can be stopped unnecessarily due to inverter shutdown. Can be prevented.

  In addition, since the operation can be continued without installing a spare converter, the installation space for the serial multiple converter can be reduced. In the case of the same rated output as before the accident, the semiconductor element needs some redundancy, but it does not affect the installation space. Further, since the inspection can be performed without stopping the converter, the reliability is improved, and not only the preventive maintenance of the equipment but also the failure rate of the system can be reduced.

  As described above, in the first embodiment and the second embodiment of the present invention, the output line voltage of each of the three phases can be set to the balanced three-phase even if any number and any capacity are combined. Therefore, restrictions on standardization and rationalization of converter design can be overcome.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of the serial multiple type | mold AC / DC converter concerning 1st Embodiment of this invention. The circuit block diagram which shows an example of the unit converter of the serial multiple converter in the 1st Embodiment of this invention. Output voltage vector showing an example of the output voltage of the serial multiple converter when the number of converters in each of the three phases of the serial multiple converter in the first embodiment of the present invention is the same and the rated capacity is also the same Figure. The output voltage vector figure which shows the Example of the output voltage of a serial multiple converter when the number of the converters of the three-phase each phase of the serial multiple converter in the 1st Embodiment of this invention is the same, and rating capacity differs. The output voltage vector figure which shows the Example of the output voltage of a serial multiple converter in case the number of converters of the three-phase each phase of the serial multiple converter in the 1st Embodiment of this invention, and rated capacity differ. The output voltage vector diagram which shows the other Example of the output voltage of a serial multiple converter in case the number of converters of the three-phase each phase of the serial multiple converter in the 1st Embodiment of this invention differs, and rated capacity is also different. . Output power (pu) of a serial multiple AC / DC converter having four converters for each phase of the serial multiple converter in the first embodiment of the present invention and having a total of 12 converters And graph showing the relationship between loss (%). The block diagram of the serial multiple type | mold AC / DC converter concerning the 2nd Embodiment of this invention. The output voltage vector figure of the serial multiple converter when any one converter of the serial multiple converter in the 2nd Embodiment of this invention stops a failure. Explanatory drawing of an example of adjustment control of the phase or magnitude | size of the output voltage of the healthy converter of the serial multiple converter in the 2nd Embodiment of this invention. Explanatory drawing of other examples of adjustment control of the phase or magnitude | size of the output voltage of the healthy converter of the serial multiple converter in the 2nd Embodiment of this invention. The flowchart which shows the control method of the serial multiplexing type | mold AC / DC converter of this invention. The output voltage vector figure in the case of carrying out the partial load operation which lowered the output voltage in the conventional serial multiple converter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Series multiple converter, 12 ... Converter, 13 ... IGBT module, 14 ... DC power supply, 15 ... Winding, 16 ... Transformer, 17 ... Fault detector, 18 ... Converter control device, 19 ... Command at normal time Value calculation means, 20 ... Failure stop command value calculation means, 21 ... Failure stop determination means, 22 ... Switching means, 23 ... Gate control circuit

Claims (12)

  A serial multiple converter formed by combining a plurality of power converters including the same or different rated capacities and connected in series to each of the three phases, and each of the three phases of the serial multiple converter Converter control device for adjusting and controlling the phase or magnitude of the output voltage of the converter connected to each of the three phases of the serial multiple converter so that the output line voltage of the phase maintains the balanced three-phase line voltage A serial multiplex AC / DC converter characterized by comprising:   2. The serial multiple AC / DC converter according to claim 1, wherein the same number of converters are connected in series for each of the three phases.   2. The serial multiple AC / DC converter according to claim 1, wherein at least one of the three phases of the converter is connected in series in a different number.   The converter control device adjusts and controls the phase or magnitude of the output voltage of the serial multiple converter when changing the number of converters to be operated, and the output line voltage of each of the three phases is a balanced three-phase line. 4. The serial multiple AC / DC converter according to claim 1, wherein an inter-voltage is held. 5.   The converter control device is configured so that the number of operating three-phase converters is constant, and the output line voltage of the three-phase each phase of the serial multiple converter is a balanced three-phase line voltage. 4. The series multiplex AC / DC converter according to claim 1, wherein the phase or the magnitude of the output voltage is adjusted and controlled. 5.   The converter control device adjusts and controls the number of operating converters of each phase of three phases or the phase or magnitude of the output voltage of the converter so that the value of the balanced three-phase line voltage is the same as the value before the change. 6. The serial multiple AC / DC converter according to claim 1, wherein the serial multiple AC / DC converter is held. 7. The converter control device according to any one of claims 1 to 6, wherein the converter control device adjusts and controls the number of operating units of each of the three phases or the phase or magnitude of the output voltage of the converter to suppress fluctuations in the efficiency of the converter as much as possible. The serial multiplex type AC / DC converter according to claim 1. A serial multiple converter in which a plurality of power converters are connected in series to each of the three phases, a fault detector for detecting that one of the converters of the serial multiple converter has failed, and the fault When the detector detects a faulty converter, a healthy converter excluding the faulty converter so that the output line voltage of the three-phase each phase of the serial multiple converter maintains a healthy voltage And a converter control device for adjusting and controlling the phase or magnitude of the output voltage of the serial multiplex type AC / DC converter. The converter control device has the same magnitude of the output voltage of each of the healthy converters excluding the converter that has failed and the phase of the phase to which the converter that has failed is connected is the same as that at the time of sound. The serial multiple AC / DC converter according to claim 8, wherein:   In the control method of the serial multiplex type AC / DC converter in which a plurality of power converters including ones having the same rated capacity and different ones are connected in series to each of the three phases and supplying three-phase AC power, the series multiplexing Adjust and control the phase or magnitude of the output voltage of the converter connected to each of the three phases of the converter, and maintain the output line voltage of each of the three phases of the serial multiple converter as a balanced three-phase line voltage A control method for a serial multiplex AC / DC converter characterized by: In the control method of the serial multiple AC / DC converter that supplies the three-phase AC power by connecting the plurality of power converters in series to each of the three phases, the converter of any one of the serial multiple converters has stopped. Each of the serial multiple converters so that the output line voltage of each phase of the three phases of the serial multiple converter becomes a predetermined voltage when none of the converters is stopped by failure. When the converter is controlled, and any of the converters is stopped by failure, the converter that has stopped by failure so that the output line voltage of the three-phase each phase of the serial multiple converter maintains a predetermined voltage when healthy. A control method for a serial multiplex AC / DC converter, wherein the phase or magnitude of the output voltage of the removed healthy converter is adjusted and controlled. When any one of the converters is out of order, a healthy converter excluding the converter that is out of order so that the output line voltage of each of the three phases of the serial multiple converters maintains a predetermined voltage when healthy. When adjusting and controlling the phase or magnitude of the output voltage of each, the magnitude of the output voltage of each healthy converter is the same, and the phase of the phase to which the faulty converter is connected is the same as that when healthy The control method of the serial multiple type | mold AC / DC converter of Claim 11 characterized by the above-mentioned.

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