JP6575289B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter that directly converts AC power supplied from a system AC power source into DC power or AC power and outputs the power.

  This type of power conversion device is provided with a plurality of power conversion devices when the voltage of the system AC power supply is high, and the AC side input terminals of these power conversion devices are connected in series to the system AC power supply. There are many. This realizes cost reduction of the device by using a semiconductor switch element having a low rated voltage for the semiconductor switch element constituting each power conversion device.

  Patent Document 1 discloses a conventional power converter of this type.

  FIG. 6 shows the first conventional example. FIG. 6 schematically shows a circuit configuration of a power conversion device including a plurality of power converter cells 50-1 to 50-n. Each power converter cell includes a first AC-DC power converter 51 that performs conversion between single-phase AC and DC, a capacitor C1 that smoothes the DC voltage of the converter 51, and DC power at both ends of the capacitor C1. A first DC-AC flow power converter 52 that converts high-frequency AC power into a high-frequency AC power, a high-frequency transformer 53 that transforms the voltage of high-frequency AC power output from the first DC-AC flow power converter 52, and A second AC-DC power converter 54 that converts AC power output from the high-frequency transformer 53 into DC power, a capacitor C2 that smoothes the DC output voltage of the second AC-DC power converter 54, and a capacitor C2 It is comprised by the 2nd direct current-alternating current power converter 55 which converts direct-current power of both ends into alternating current power.

  The AC input terminals of the power converter cells 50-1 to 50-n are connected in series to each other and connected to the AC power supply 59 of the system. The AC output terminals of the power converter cells 50-1 to 50-n can be connected in series with each other and connected to a load (not shown).

  As the number of stages of power converter cells 50-1 to 50-n connected in series increases, the voltage rating of each cell can be reduced and the AC output voltage can be multi-level (multi-level).

  FIG. 7 shows a second conventional example. The power converter cells 50-1 to 50-n in the second conventional example are DC-AC current power conversions in the final stage of the power converter cells 50-1 to 50-n in the first conventional example. The device 55 is omitted to output DC power, and the DC output terminal of the final stage AC-DC power converter 54 is connected in series.

  According to the second conventional example, the n-stage power converter cells 50-1 to 50-n can obtain a DC voltage n times the rated DC output voltage of the one-stage power converter cell 50.

  FIG. 8 shows a third conventional example. In the third conventional example, the DC output terminals of the plurality of power converter cells 50-1 to 50-n are connected in parallel instead of being connected in series in the second conventional example.

  According to the third conventional example, the power converter cells 50-1 to 50-n are arranged in n stages, so that the output current capacity is n times the rated current capacity of the one-stage power converter cell 50. The current capacity can be increased.

JP 2005-073362 A

  Since the conventional power converters having a plurality of power converter cells as described above are connected to the AC power source of the system by connecting the AC input terminals of each power converter cell in series, the voltage is high. The AC power of the AC power supply of the system can be directly converted into AC power or DC power without using a transformer or the like.

  However, if a failure that opens the electrical circuit occurs in the switching element inside any one of the plurality of power converter cells, the supply of input power to all the power converter cells is cut off. The entire apparatus is shut down and power cannot be supplied to the load. For this reason, the conventional power converter has a problem of lack of reliability.

  In order to solve such a problem, the present invention provides a power conversion device in which at least AC input terminals of a plurality of power converter cells are connected in series to each other and connected to an AC power source. If a failure that opens one electrical circuit (open failure) occurs, only the failed power converter cell is shut down and the operation continues with the remaining normal power converter cells. It is an object of the present invention to provide a highly reliable power converter that does not stop the entire operation of the converter.

  In order to solve the above-described problems, the present invention includes a plurality of power converter cells that convert input AC power into DC power or AC power and output the power, and at least the AC input terminals of the power converter cells are mutually connected. In a power converter configured to be connected in series and connected to an AC power source, a short circuit that short-circuits the AC input side of each power converter cell when a failure occurs such that the switching element opens the circuit. A switch is provided.

  In the present invention, each of the power converter cells can be connected to a DC load or an AC load by connecting their DC or AC output terminals in parallel or by connecting them in series.

  The short-circuit switch on the AC input side of the power converter cell may be constituted by a semiconductor switch element that short-circuits the DC output terminal of the AC-DC power converter on the input side of the power converter cell.

  Moreover, the switch for short-circuiting the AC input side of the power converter cell can be constituted by a bidirectional semiconductor switch that short-circuits the AC input terminal of each power converter cell.

  Furthermore, the short-circuit switch on the AC input side of the power converter cell may be configured by a mechanical switch that short-circuits the AC input terminal of each power converter cell.

  When the output ends of the plurality of power converter cells are connected in series, it is preferable to provide a shorting switch for short-circuiting the output ends of the power converter cells.

  In the power converter configured by connecting at least AC input terminals of a plurality of power converter cells in series with each other and connected to an AC power source, an internal switching element is provided in any one of the plurality of power converter cells. According to the present invention, when an open failure that opens the electric circuit occurs, the failure is caused by shutting down the faulty power converter cell and short-circuiting the AC input side by turning on the short-circuit switch. Since the supply of AC power to healthy cells other than the power converter cell can be continued, the power conversion device can continue without stopping the power supply to the load.

  Therefore, the power conversion device according to the present invention continues the operation of the remaining healthy power conversion cells without stopping the entire operation even when one of the plurality of power conversion cells fails, and supplies power to the load. Since supply can be continued, the reliability of a power converter device can be improved.

The circuit block diagram which shows the power converter device by 1st Example of this invention. The circuit block diagram which shows the power converter device by 2nd Example of this invention. The circuit block diagram which shows the power converter device by 3rd Example of this invention. The circuit block diagram which shows the power converter device by 4th Example of this invention. The circuit block diagram which shows the power converter device by 1st Example of this invention. The block circuit block diagram which shows the 1st example of the conventional power converter device. The block circuit block diagram which shows the 2nd example of the conventional power converter device. The block circuit block diagram which shows the 3rd example of the conventional power converter device.

  Embodiments of the present invention will be described with reference to the embodiments shown in the drawings.

  FIG. 1 shows the configuration of a power conversion apparatus according to a first embodiment of the present invention.

  In FIG. 1, 10-1 to 10-n are n (n is a natural number of 2 or more) power converter cells having the same configuration. Each power converter cell 10 includes a converter circuit CN1 configured by a diode that converts AC power into DC power, an AC-DC power converter 11 configured by a smoothing capacitor C1, and the AC-DC power converter. 11 includes a DC-DC power converter 12 that converts the DC output of 11 into DC power of a predetermined voltage.

  The DC-DC power converter 12 converts the DC power output from the AC-DC power converter 11 into high-frequency AC power, and converts the AC output voltage of the inverter circuit IN1 into a predetermined AC voltage. Converter circuit CN2 composed of a high-frequency transformer T, a transistor for converting AC power output from the high-frequency transformer T into DC power of a predetermined voltage, and a DC for smoothing the DC output voltage of the converter circuit CN2 It is comprised with the reactor L2 and the capacitor | condenser C2.

  In order to short-circuit the DC output terminal of the converter circuit CN1 of the AC-DC power converter 11, a semiconductor switch S1 configured by connecting a transistor Tr such as IGBT and a diode D1 in antiparallel is connected in parallel thereto. ing. This semiconductor switch S1 is turned off when the power converter cell 10 is operating normally, and opens the DC output terminal of the converter circuit CN1. When the switching transistor constituting the converter circuit CN2 of the DC-DC power converter 12 in the cell has a failure to open the electric circuit, the semiconductor switch S1 is turned on and the DC output terminal of the converter circuit CN1 is turned on. Operates to short circuit.

  The AC input terminals of the AC-DC power converters 11 in the input stages of the n power converter cells 10-1 to 10-n configured as described above are connected in series to each other and connected to the AC power supply 18 of the system. The The DC output terminals of the DC-DC power converters 12 in the output stages of the power converter cells 10-1 to 10-n are connected in parallel to each other and connected to the DC load 19, and from each power converter cell. DC power is supplied to the load 19 in parallel.

  Since the power converter configured in this way shares the voltage among the n power converter cells 10 even when the AC power supply 18 is at a high voltage, each power converter cell is configured with a cell having a low voltage rating. can do. And since direct-current power is supplied in parallel from the n power converter cells 10 to the load 19, the current capacity of the load 19 can be increased. For this reason, the power conversion device of the present invention is optimally used as a power source that requires a large current at a low DC voltage, such as a server power source in a data center or the like.

  In this power converter, when all the power converter cells are operating soundly, the semiconductor switch S1 for short-circuiting each power converter cell is given an OFF command from a control device (not shown) and turned OFF ( Non-conducting). Thereby, since the DC output terminal of the converter circuit CN1 of each power converter cell 10 is opened, the AC power supplied from the AC power source 18 is converted into DC power by the AC-DC power converter 11, and the DC power is supplied. -It is supplied to the DC power converter 12, and this DC power is converted into DC power of a predetermined voltage by the DC-DC power converter 12 and supplied to the load 19 in parallel.

  Here, for example, in the power converter cell 10-1, when an open fault that opens the electric circuit occurs in one of the switching transistors constituting the inverter circuit IN1 of the DC-DC power converter 12, the total power conversion The input current supplied in series from the AC power source 18 to the converter cells 10-1 to 10-n is interrupted by the failed switching transistor of the inverter circuit IN1 of the power converter cell 10-1, so that the total power conversion is performed. The unit cell stops supplying power, and power supply to the load 19 becomes impossible.

  In order to prevent the power supply to the load 19 from being stopped, in the present invention, when an open failure as described above occurs, a control device (not shown) detects this and immediately generates the failure. A command to stop operation is given to the power converter cell 10-1 and an on command is given to the shorting semiconductor switch S1. As a result, the power converter cell 10-1 stops its operation, stops the power conversion operation, and the semiconductor switch S1 is turned on, whereby the DC output terminal of the converter circuit CN1 of the power converter cell 10-1 is Shorted.

  As a result, the input current supplied from the AC power supply 18 to the power conversion device is connected to the failed power converter cell in series through the converter circuit CN1 and the semiconductor switch S1 of the failed power converter cell 10-1. Therefore, the supply of DC power from the healthy power converter cell to the load 19 can be continued.

  FIG. 2 shows the construction of the second embodiment of the present invention.

  In the first embodiment of FIG. 1, when an open fault that opens the electric circuit occurs in the converter circuit CN <b> 1 of the power converter cell 10, the backup cannot be performed, so the second embodiment improves this. To do.

  In the power conversion device of the second embodiment, the configuration of each power converter cell 10 and the connection configuration of n power converter cells 10-1 to 10-n are the same as those of the first embodiment shown in FIG. It is the same as a power converter. However, instead of the short-circuit semiconductor switch S1, a two-way semiconductor switch (so-called AC switch) S2 configured by connecting two switching transistors and diodes connected in reverse parallel and connected in reverse series is used. The point is different.

  The bidirectional semiconductor switch S2 is connected in parallel to the AC input terminal of each power converter cell 10. For this reason, the bidirectional semiconductor switch S2 is turned off (non-conducting) when each power converter cell 10 is operating sanely, and an open circuit fault has occurred that opens the circuit inside. When it is turned on (conductive), it operates to short-circuit the AC input terminals of the respective power converter cells 10.

  Similarly to the power conversion device of the first embodiment, the power conversion device of the second embodiment is used for short-circuiting each power converter cell when all the power converter cells are operating soundly. The bidirectional switch S2 is turned off (non-conducting) by receiving an off command from a control device (not shown). Thereby, the AC input terminal of the converter circuit CN1 of each power converter cell 10 is opened, so that the AC current supplied from the AC power source 18 flows in series to the converter circuit CN1 of each power converter cell 10. The AC power supplied thereby is converted into DC power by the AC-DC power converter 11 in each power converter cell 10 and supplied to the DC-DC power converter 12, and this DC-DC power converter. At 12, this is converted into DC power of a predetermined voltage and supplied to the load 19 in parallel.

  Here, for example, in the power converter cell 10-1, when one of the diodes constituting the converter circuit CN1 of the DC-AC converter 11 has an open fault that opens an electric circuit, the AC power source 18 The input current supplied in series to the power converter cells 10-1 to 10-n is interrupted by the open failure diode of the converter circuit CN1 of the power converter cell 10-1. Thereby, the power supply to all the power converter cells is stopped, and the power supply to the load 19 becomes impossible.

  In order to prevent the power supply to the load 19 from being stopped, in the second embodiment, when an open failure as described above occurs, a control device (not shown) detects this and immediately generates the failure. The power converter cell 10-1 is given a command to stop operation, and the short-circuit bidirectional switch S2 is given a turn-on command. As a result, the power converter cell 10-1 stops the power conversion operation and the bidirectional semiconductor switch S2 is turned on, whereby the AC input terminal of the converter circuit CN1 of the power converter cell 10-1 is short-circuited. .

  For this reason, the input current supplied from the AC power source 18 to the power conversion device bypasses the failed power converter cell through the bidirectional semiconductor switch S2 at the AC input end of the failed power converter cell 10-1. Since it flows to the other healthy power converter cell connected in series with this, supply of DC power from the healthy power converter cell to the load 19 can be continued.

  FIG. 3 shows the configuration of the third embodiment of the present invention.

  In the third embodiment, a mechanical switch S3 such as a relay is used instead of the bidirectional semiconductor switch S2 in the second embodiment of FIG. Similarly to the power converter of the second embodiment, this switch S3 is also turned off when all the power converter cells are operating soundly so as to open an electric circuit inside the power converter cell. When an open failure occurs, it is turned on and operates to short-circuit the AC input terminal of each power converter cell.

  Since other configurations are the same as those of the second embodiment, detailed description thereof is omitted.

  Also in the third embodiment, when an open failure that opens the electric circuit occurs in one of the power converter cells 10, the operation of the failed power converter cell 10 is stopped, and the switch S 3 is turned on. Turned on and shorts its AC input. As a result, the input current is continuously supplied to the other healthy power converter cell 10 connected in series with the failed power converter cell without being interrupted. The supply of DC power to the load 19 can be continued.

  FIG. 4 shows the configuration of the fourth embodiment of the present invention.

  In the fourth embodiment, the connection of the DC output terminals of the plurality of power converter cells 10-1 to 10-n in the first embodiment shown in FIG. 1 is changed to a series connection. According to the fourth embodiment, since the DC output terminals are connected in series, the output voltage can be increased.

  In the fourth embodiment, since the DC output terminals of the plurality of power converter cells 10-1 to 10-n are connected in series, an electric circuit is connected to the transistor of the converter CN2 at the output stage of the DC-DC power converter 12. In order to take measures when an open circuit failure occurs, a DC switch S4 having the same configuration as the DC switch S1 on the input side is connected in parallel with the DC output terminal of each power converter cell 10. Other configurations are the same as those of the first embodiment.

  When an open circuit failure that opens an electric circuit occurs in the inverter circuit IN1 of the input stage of the DC-DC power converter 12 of each power converter cell 10, as in the first embodiment, the input side semiconductor switch By turning on S1 and shorting the AC input terminal, the supply of AC power to the healthy power converter cell 10 is continued, and the operation stop of the entire power converter is avoided.

  If an open circuit failure that opens the circuit in the converter circuit CN2 at the output stage of the DC-DC power converter 12 of each power converter cell 10 occurs, the DC switch S4 on the output side is turned on and DC output is performed. By short-circuiting the ends, it is possible to prevent a healthy DC power supply from the power converter cell 10 from being cut off from the load, and to avoid the operation stop of the entire power converter.

  FIG. 5 shows the structure of the fifth embodiment of the present invention.

  In the fifth embodiment, an inverter circuit IN2 further converts DC power into AC power at the DC output terminal of the DC-DC power converter 12 of each power converter cell 10 in the second embodiment shown in FIG. Are connected to obtain AC output. The AC output terminals of the power converter cells 10 are connected in parallel to supply AC power from each power converter cell 10 to the AC load 19A in parallel. Other configurations are the same as those of the second embodiment of FIG. According to the fifth embodiment, it is possible to supply power to a large-capacity AC load having a large current capacity.

  Also in the fifth embodiment, as in the second embodiment, in any of the plurality of power converter cells 10-1 to 10-n, an open failure that opens the electric circuit in the converter circuit CN1 occurs. When it occurs, the operation of the failed power converter cell 10 is stopped and the bidirectional semiconductor switch S2 at the AC input end is turned on to short-circuit the AC input end. As a result, the input current from the AC power supply 18 continues to flow to the other healthy power converter cell 10 without being cut off, so the supply of DC power from the healthy power converter cell 10 to the load 19 is continued. can do.

10-1 to 10-n: Power converter cell 11: AC-DC power converter 12: DC-DC power converter 18: System AC power supply 19: DC load 19A: AC load CN1, CN2: converter circuit IN1, IN2 : Inverter circuit T: High frequency transformer L1, L2: Reactor C1, C2: Capacitor

Claims (7)

  Provided with a plurality of power converter cells that convert input AC power into DC power or AC power and output, and at least the AC input terminals of each of the power converter cells are connected in series to each other and connected to an AC power source. In the power conversion device, the power conversion is characterized in that a switch for short-circuiting is provided in each of the power converter cells to short-circuit the AC input side when a failure occurs such that the switching element opens the circuit. apparatus.   The power converter according to claim 1, wherein each of the power converter cells is connected to a DC load or an AC load by connecting its DC or AC output terminals in parallel.   2. The power converter according to claim 1, wherein each of the power converter cells has a DC or AC output terminal connected in series and connected to a DC load or an AC load.   The short-circuit switch on the AC input side of the power converter cell is a semiconductor switch element that short-circuits the DC output terminal of the AC-DC power converter on the input side of each power converter cell. The power conversion device according to any one of 1 to 3.   4. The short-circuit switch on the AC input side of the power converter cell is a bidirectional semiconductor switch that short-circuits the AC input terminal of each of the power converter cells. The power converter described.   4. The switch for short-circuiting on the AC input side of the power converter cell is a mechanical switch for short-circuiting the AC input terminal of each of the power converter cells. 5. Power converter.   The power converter according to claim 3, wherein a short-circuit switch for short-circuiting the power converter cell is provided at an output end of each of the power converter cells.

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