JP6102364B2 - Grid connection system for fuel cells - Google Patents

Description

  The present invention relates to a fuel cell grid interconnection system that links a fuel cell and a commercial power supply system.

  A fuel cell grid interconnection system that links a power generation unit such as a fuel cell and a commercial power supply system (hereinafter also referred to as “system”) includes a power conditioner. The power conditioner has a converter unit and a grid interconnection inverter unit in order to convert the DC power generated by the power generation unit into AC power that can be supplied to the system. The converter unit boosts the DC voltage generated by the power generation unit. The system interconnection inverter unit converts the DC voltage boosted by the converter unit into an AC voltage synchronized with the system (for example, see Patent Document 1).

JP 2011-97727 A

  In the grid interconnection inverter unit, it is possible to control the output current, but the output voltage is constant. If an excessive current continues to be output in the grid interconnection inverter unit even though electricity is not sufficiently output in the fuel cell, the converter unit stops.

  Specifically, the control current amount of the grid interconnection inverter that controls the capacity of electricity at the start, stop, and output adjustment of the fuel cell grid interconnection system is compared with the output current amount of the fuel cell. May grow. As a result, when the output voltage of the fuel cell drops below the minimum input allowable voltage value as the allowable voltage of the converter unit, the converter unit is in an unstable state that repeatedly stops and immediately returns.

  It is an object of the present invention to provide a fuel cell grid interconnection system that prevents a converter unit from stopping when electricity is not sufficiently output in a fuel cell.

  The present invention provides a fuel cell, and a converter unit that converts a DC voltage output from the fuel cell to a predetermined DC voltage when a DC voltage output from the fuel cell is greater than a minimum allowable input voltage value; A grid-connected inverter unit that converts a DC voltage output from the converter unit into an AC voltage and supplies it to the system, and a converter unit input voltage detection that detects a DC voltage output from the fuel cell and input to the converter unit And the DC current detected by the converter input voltage detector is less than or equal to a predetermined value near the minimum input allowable voltage value, the AC current output from the grid interconnection inverter is reduced And a control unit that performs control on the grid interconnection inverter unit.

  ADVANTAGE OF THE INVENTION According to this invention, when the electricity is not fully output in a fuel cell, the grid connection system for fuel cells which prevents that a converter part stops can be provided.

1 is a block diagram showing a fuel cell grid interconnection system 1 according to an embodiment of the present invention. FIG.

  Hereinafter, a fuel cell system interconnection system according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a fuel cell grid interconnection system 1 according to an embodiment of the present invention.

  As shown in FIG. 1, a fuel cell grid interconnection system 1 includes a fuel cell 10, a DC / DC converter 20 as a converter section, a grid interconnection inverter 30 as a grid interconnection inverter section, and a converter section input. A voltage detection unit 40 and a control unit 50 are provided. The fuel cell grid interconnection system 1 links a fuel cell 10 that is a power generation unit and a commercial power supply system 60 (hereinafter also referred to as “system 60”).

  The fuel cell 10, the DC / DC converter 20, and the grid interconnection inverter 30 are electrically connected in series in this order. More specifically, the DC / DC converter 20 and the grid interconnection inverter 30 are electrically connected by a DC bus. Converter unit input voltage detection unit 40 is electrically connected between fuel cell 10 and DC / DC converter 20. Moreover, the control part 50, the DC / DC converter 20, the grid connection inverter 30, and the converter part input voltage detection part 40 are each electrically connected. The control unit 50 can control the DC / DC converter 20, the grid interconnection inverter 30, and the converter unit input voltage detection unit 40.

  The fuel cell 10 is composed of, for example, a SOFC (solid oxide fuel cell) that is a high-temperature fuel cell. In the fuel cell 10, power generation is performed by reacting hydrogen and oxygen. The DC voltage generated by the fuel cell 10 is output to the DC / DC converter 20.

  The DC / DC converter 20 converts (boosts) a DC voltage of about 90V to 160V output from the fuel cell 10 to a predetermined DC voltage. The predetermined DC voltage is, for example, a voltage (for example, DC 280V) that can generate a voltage (for example, AC 200V) that can be supplied to the system 60 in the grid interconnection inverter 30, and this output voltage is a fixed value. is there.

  Therefore, the DC / DC converter 20 converts the DC voltage output from the fuel cell 10 into a predetermined DC voltage when the DC voltage output from the fuel cell 10 is greater than the minimum allowable input voltage value. Conversely, the DC / DC converter 20 stops the conversion for boosting the DC voltage when the DC voltage output from the fuel cell 10 is smaller than the minimum input allowable voltage value. The minimum input allowable voltage value is, for example, 80V.

  The grid interconnection inverter 30 converts the DC voltage output from the DC / DC converter 20 into a predetermined AC voltage (for example, AC 200 V) that can be supplied to the grid 60 and supplies the converted voltage to the grid. Since the grid interconnection inverter 30 supplies an AC voltage to the grid, the value of the AC voltage output from the grid interconnection inverter 30 is a fixed value. On the other hand, the grid interconnection inverter 30 can control the value of the current output from the grid interconnection inverter 30.

  The converter unit input voltage detection unit 40 detects a DC voltage value output from the fuel cell 10 and input to the DC / DC converter 20. The detected DC voltage value is output to the control unit 50.

  The control unit 50 is configured by a sequencer, and controls a series of operations from startup to power generation for the fuel cell 10. Specifically, the control unit 50 is electrically connected to an auxiliary machine (not shown) provided to generate power in the fuel cell 10 and controls the auxiliary machine and the like. Here, the auxiliary machine is, for example, a blower (not shown) for supplying air to the fuel cell 10 or a booster (not shown) for supplying fuel to the fuel cell 10.

  Further, the control unit 50 determines whether or not the DC voltage value detected by the converter unit input voltage detection unit 40 is equal to or less than a predetermined value near the minimum input allowable voltage value, for example, a value of 90V. When control unit 50 determines that the DC voltage value detected by converter unit input voltage detection unit 40 is equal to or less than a predetermined value near the minimum input allowable voltage value, AC current output from grid interconnection inverter 30 is determined. Control to reduce the power is performed on the grid interconnection inverter 30.

According to the fuel cell grid interconnection system 1 of the present embodiment, the following effects can be obtained.
As described above, the fuel cell grid interconnection system 1 includes the converter unit input voltage detection unit 40 that detects the DC voltage output from the fuel cell 10 and input to the DC / DC converter 20 as the converter unit, and the converter unit. When the DC voltage detected by the input voltage detection unit 40 is equal to or less than a predetermined value near the minimum input allowable voltage value, control for reducing the AC current output from the grid interconnection inverter 30 is performed. 30 is provided.

  For this reason, although the fuel cell 10 does not sufficiently output electricity, it is possible to prevent the grid-connected inverter 30 from continuing to output excessive current. Thereby, when the DC / DC converter 20 does not output enough electricity, it is possible to prevent an unstable operation in which the DC / DC converter 20 stops and immediately returns. As a result, damage to the cell stack of the fuel cell 10 can be suppressed.

  Further, since the alternating current output from the grid interconnection inverter 30 can be reduced, it is not necessary to vary the output voltage in the DC / DC converter 20, and an expensive DC / DC converter 20 with variable output voltage is used. There is no need. That is, an inexpensive DC / DC converter 20 whose output voltage cannot be controlled and whose output voltage is a fixed value can be used. As a result, the cost for configuring the fuel cell grid interconnection system 1 can be reduced.

  Further, the control unit 50 determines that the AC current output from the grid interconnection inverter 30 when the DC voltage detected by the converter unit input voltage detection unit 40 is equal to or less than a predetermined value near the minimum allowable input voltage value. Reduce. For this reason, before the direct current voltage output from the fuel cell 10 becomes smaller than the minimum input allowable voltage value, the alternating current output from the grid interconnection inverter unit can be reduced in advance. As a result, the controller 50 can take measures so that the DC / DC converter 20 does not stop the conversion for boosting the DC voltage with a margin early.

  The present invention is not limited to the above embodiment, and can be modified within the technical scope described in the claims. For example, the fuel cell 10 is configured by SOFC, but is not limited to SOFC. For example, PEFC (solid polymer fuel cell) or the like may be used. Moreover, the value of each voltage etc. are not limited to the value as described in this embodiment.

DESCRIPTION OF SYMBOLS 1 Fuel cell system interconnection system 10 Fuel cell 20 DC / DC converter (converter part)
30 Grid-connected inverter (Grid-connected inverter section)
40 Converter unit input voltage detection unit 50 Control unit

Claims (1)

A fuel cell;
A converter unit that converts the DC voltage output from the fuel cell to a predetermined DC voltage when the DC voltage output from the fuel cell is greater than a minimum input allowable voltage value;
A grid-connected inverter unit that converts a DC voltage output from the converter unit into an AC voltage and supplies the AC voltage to the system;
A converter unit input voltage detection unit for detecting a DC voltage output from the fuel cell and input to the converter unit;
Control that reduces the alternating current output from the grid interconnection inverter when the DC voltage detected by the converter input voltage detector is equal to or less than a predetermined value near the minimum allowable input voltage value. A fuel cell grid interconnection system comprising: a control unit that performs the grid interconnection inverter unit.

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