JPH06101346B2 - Operating method of fuel cell power generator - Google Patents

Description

The present invention relates to a fuel cell power generator in which a DC output of a fuel cell is converted into an AC output by an inverter, and a dummy resistor connected between the fuel cell and the inverter is used as an electric load. The present invention relates to a stop control method for a fuel cell power generation device, in which an increase in the reaction gas pressure in the fuel cell is reduced by controlling during shutoff.

In this type of power generator, it is required to stop as early as possible in an emergency to remove obstacles to minimize damage and to reduce the impact on the power generator by stopping at this time. The fuel cell power generation system is generally stopped by closing the valves for the fuel gas at the fuel cell inlet and the air that is the oxidant gas for the fuel cell, and for the inverter at the same time by shutting off the AC and DC circuit breakers. Be done. The current flowing through the fuel cell is instantaneously interrupted by the interruption of the inverter, but it takes some time to close the fuel gas and air in the fuel cell. Therefore, the consumption of the fuel gas and the air used for the power generation reaction in the fuel cell stops at the same time as the interruption of the current, so that the pressure in the fuel cell temporarily rises. At this time, since the hydrogen component in the fuel gas is higher than the oxygen component in the air, the pressure on the fuel gas side in the fuel cell rises higher than the pressure on the air side, and a differential pressure appears. This pressure difference is not preferable because it may damage the fuel cell and may also deteriorate the power generation characteristics due to the impact applied to the fuel cell. In addition, this differential pressure is required to be as small as possible. In the past, this differential pressure was attempted to be reduced by a fluid device such as a safety valve, but there are restrictions on the type of device and mounting position, so there is a limit to rapid operation, and the occurrence of the above differential pressure must be kept below a specified value. Was difficult.

In order to eliminate the conventional drawbacks, the present invention electrically consumes the excess gas in the fuel cell accompanying the shutdown by controlling a dummy resistor provided between the fuel cell and the inverter, The purpose is to reduce the differential pressure. To this end, a fuel cell that generates power by supplying a fuel gas and an oxidant gas such as air, an inverter that converts the DC output of the fuel cell into an AC output, and an inverter between the fuel cell and the inverter. In a method of operating a fuel cell power generator, which comprises a dummy resistor that can be turned on and off via a switch to keep the input voltage of the fuel cell below a predetermined value, the dummy resistor is turned on when the fuel cell power generator is turned off. Then, the charging time is selected based on the load current value immediately before the interruption of the electric load so that the differential pressure between the fuel gas side and the oxidant gas side of the fuel cell becomes a predetermined value or less, and the selection is performed. It is achieved by cutting off the dummy resistor after the predetermined time.

This dummy resistor has been conventionally used exclusively for the purpose of facilitating the design of the inverter, which will be described with reference to the drawings. FIG. 1 shows the voltage-current characteristics of the fuel cell. V ₀ is a no-load voltage, and currents I _{1 to} I ₂ and voltages V _{1 to} V ₂ are practically used as a power generator. This V ₁ ~ V ₂
Is lower than the no-load voltage V ₀ ,
It is uneconomical to design with V ₀ . For this reason, a dummy resistor is provided between the fuel cell and the inverter, and this dummy resistor is turned on at the time of start-up, and the dummy resistor is lowered to I _{1 in} FIG. ₁ to reduce the voltage to V ₁ before connecting to the inverter. Also, when the inverter is turned off, the dummy signal is first turned on by the stop signal, and then the inverter is turned off. When the inverter is turned off, only the voltage up to V ₁ is applied. By using the dummy resistor in this manner, the inverter is the voltage up to V _1, and so can be designed in a range of V ₁ ~V _2, may be economical and efficient.

The present invention intends to reduce the above-mentioned differential pressure by using this dummy resistor, and the outline will be described with reference to FIG. Fuel gas from the fuel gas inlet valve 2 and air from the air inlet valve 3 are sent to the fuel cell 1 to the fuel gas chamber 4 and the air chamber 5, respectively, and hydrogen and oxygen therein generate a power generation reaction, and the electrode 6 Power generation output is guided to the outside. Then, after the power generation is possible, the DC breaker 7 is turned on, the dummy resistor switch 8 is closed, and a current is passed through the dummy resistor 9.
The voltage and current values of the fuel cell at this time are V ₁ and I _{1 in} FIG. Then close the DC breaker 10 and close the inverter 11
Is driven to close the effective current breaker 12 to start feeding power to an electric load (not shown). The dummy resistor 9 is then no longer needed and the switch 8 is opened.

On the other hand, when the apparatus 11 is stopped, for example, when the inverter 11 is cut off when the electric load is short-circuited, the switch 8 is turned on in advance and the dummy resistor 9 is connected to the fuel cell 1 to reduce the control angle of the inverter or the breaker. Open the circuit of 10,12 to disconnect the inverter from the fuel cell. By the way, according to the conventional design concept of the dummy resistor, when the DC breaker 10 of the inverter is opened, it is not necessary to insert the dummy resistor 9 into the circuit anymore, so that the DC breaker 10 is opened. At the same time, the switch 8 was cut off and the dummy resistor 9 was cut off.

The present invention is based on the finding that the generation of the above-mentioned differential pressure in the fuel cell can be reduced by slightly delaying the disconnection of the dummy resistor, and the embodiments will be described below.

The embodiment shown in FIG. 3 is an example in which a timer is used. When the open command contact 21 of the DC circuit breaker 10 shown in FIG. The closing relay 24 is excited to turn on the dummy resistor 9 first, and the timer 25 delays for a short time to excite the trip relay 27 of the DC breaker 10 via the contact 26 to open the DC breaker 10. After that, the contact 29 is opened by the timer 28 after the predetermined time limit to degauss the closing relay 24 of the dummy resistor closing switch 8, and the breaking relay 31 of the dummy resistor closing switch 8 is excited via the contact 30 to open the dummy resistor. Detach. FIG. 3 shows an example of the principle of connection. It goes without saying that it is easy to adopt a circuit system different from this depending on the mode of the closing and breaking relays, or to make all of them contactless.

As the dummy resistor 9, a type including an inductance component is often adopted as compared with a pure DC resistor. Also, as shown in FIG. 4, a DC resistance (or one in which this and an inductance are connected in series) 9a and a capacitor 9b
It is also possible to use a series of and.

Since the magnitude of the differential pressure generated when the device is stopped depends on the amount of fuel gas consumed immediately before the stop, and thus the load current, the output DC current is detected by the detector 32 as shown in FIG. However, the value of the resistance 9C of the dummy resistor may be changed in advance, or a plurality of dummy resistors 9C may be used as shown in FIG.
It is also possible to obtain a combination that matches the load current value in advance using a circuit having A, 9B, and 9C, and then turn on the dummy resistors of this combination at the same time when the inverter is cut off. Fourth, to simplify the circuit
It is desirable to use a single dummy resistor as shown in the figure to control the closing time based on the load current value. In this case, instead of detecting the DC current, it is also possible to detect the AC output current of the inverter and perform selective control of the closing time of the dummy resistor. Furthermore, it may be convenient in some cases to monitor the pressure of the reaction gas in the fuel cell to control the charging time. The switch 8 is a transistor,
It can be replaced with a thyristor or the like.

As described above, according to the present invention, when the fuel cell power generator is stopped, the dummy resistor, which is conventionally separated immediately after being charged, is continuously controlled from the viewpoint of limiting the reaction gas pressure increase of the fuel cell. Since this is done, there is an effect that the adverse effect on the fuel cell can be prevented more quickly and without adding extra cost, as compared with the control by the conventional fluid equipment. Furthermore, by controlling the closing time of the dummy resistor based on the load current value immediately before the interruption of the electric load, the abnormal differential pressure of the reaction gas generated during the interruption of the fuel cell is prevented and the dummy resistor There is an effect that the configuration can be simplified.

[Brief description of drawings]

FIG. 1 is a current-voltage characteristic diagram of a fuel cell, FIG. 2 is a circuit connection diagram for explaining a closing sequence of dummy resistors, and FIGS. 3 and 4 are examples for explaining the method of the present invention. FIG. 5 is a partial circuit diagram of FIG. 5, and FIG. 5 and FIG. 6 are explanatory views of a circuit for varying the resistance value of the dummy resistor. 1 ... Fuel cell, 8 ... Dummy resistor closing switch, 9 ... Dummy resistor, 11 ... Inverter, 25, 28 ... Timer, 31 ... Current detector.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shira Ishii 1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. (72) Teruo Iida 1 Nitta Tanabe, Kawasaki-ku, Kawasaki-shi, Kanagawa No. 1 in Fuji Electric Co., Ltd. (72) Inventor Naoya Eguchi 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Inside Fuji Electric Co., Ltd. (56) Reference JP-A-56-112073 (JP, A)

Claims (1)

[Claims] 1. A fuel cell for generating power by supplying a fuel gas and an oxidant gas such as air, an inverter for converting a DC output of the fuel cell into an AC output, and between the fuel cell and the inverter. In a method of operating a fuel cell power generator, which comprises a dummy resistor that can be turned on and off via a switch in order to keep the input voltage of the inverter below a predetermined value, the dummy resistor is turned off when the fuel cell power generator is turned off. The charging time is selected to be a predetermined time such that the differential pressure between the fuel gas side and the oxidant gas side of the fuel cell becomes a predetermined value or less based on the load current value immediately before the interruption of the electric load, A method of operating a fuel cell power generator, comprising cutting off a dummy resistor after a selected predetermined time.