JPS6341193B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fuel cell power generation device in which a DC output of a fuel cell is converted into an AC output using an inverter, in which a dummy resistor connected between the fuel cell and the inverter is used as an electrical load. The present invention relates to a stop control method for a fuel cell power generation device, which reduces the rise in reaction gas pressure within a fuel cell by controlling during shutdown.

In this type of power generation device, it is required to stop the power generation device as soon as possible in an emergency to remove the obstacle and minimize damage, and to reduce the impact on the power generation device by stopping at this time. Generally, to stop a fuel cell power generation system, for a fuel cell, close the fuel gas and oxidant gas air valves at the fuel cell inlet, and for an inverter, simultaneously shut off the AC and DC sides. It is done by doing. When the inverter breaks down, the current flowing to the fuel cell is instantly cut off, but
It takes some time to close off the fuel gas and air in the fuel cell. Therefore, the consumption of the fuel gas and air used in the power generation reaction within the fuel cell stops at the same time as the current is cut off, and the pressure within the fuel cell temporarily increases. 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 increases more than the pressure on the air side within the fuel cell, resulting in a differential pressure. This differential pressure not only has the risk of damaging the fuel cell, but also is undesirable because it causes a shock to the fuel cell, degrading the power generation characteristics. Further, this differential pressure is required to be as small as possible. Conventionally, attempts have been made to reduce this differential pressure using fluidic devices such as safety valves, but there are restrictions on the type and mounting location of the devices, which limits quick operation. was difficult.

In order to eliminate the conventional drawbacks, the present invention electrically consumes excess gas in the fuel cell due to stoppage by controlling a dummy resistor installed between the fuel cell and the inverter. The purpose is to reduce differential pressure. This object is achieved according to the invention by switching on the dummy resistor for a time sufficient to quench the reactant gas when the fuel cell power plant is quenched.

This dummy resistor has been conventionally used solely for the purpose of facilitating the design of the inverter, and will be explained based on the drawings. FIG. 1 shows the voltage-current characteristics of the fuel cell, where V _p is the no-load voltage, and the currents I ₁ to I ₂ and voltages V ₁ to _{V 2} are in the range that is practically used as a power generation device. This V ₁ to _{V 2} is lower than the no-load voltage V ₀ , so the inverter is connected to the no-load voltage
It is uneconomical to design with V ₀ . For this reason, a dummy resistor is installed between the fuel cell and the inverter, and this dummy resistor is inserted at startup, and I ₁ in Figure 1 is set.
Connect it to the inverter after lowering the voltage to V ₁ by using a dummy resistor. Also, when the inverter is stopped, a dummy resistor is first turned on in response to a stop signal, and then the inverter is turned off. When the inverter is turned off, only a voltage up to _V1 is applied. By using the dummy resistor in this way, the inverter can be designed with a voltage up to V ₁ and in the range of V ₁ to _{V 2} , which is economical and efficient.

The present invention aims to reduce the above-mentioned differential pressure by using this dummy resistor, and will be schematically explained with reference to FIG. 2. In the fuel cell 1, fuel gas from a fuel gas inlet valve 2 and air from an air inlet valve 3 are sent to a fuel gas chamber 4 and an air chamber 5, respectively, and a power generation reaction occurs with hydrogen and oxygen among them, and an electrode 6 The power generation output is guided to the outside. Then, after reaching a state in which power generation is possible, the DC side disconnector 7 is turned on, the dummy resistor switch 8 is closed, and current is allowed to flow through the dummy resistor 9. At this time, the voltage and current values of the fuel cell are the first
This becomes V ₁ and I ₁ in the figure. After that, DC and disconnector 10
is closed to drive the inverter 11, and the AC switch breaker 12 is closed to start supplying power to an electrical load (not shown). The switch 8 is then opened since the dummy resistor 9 is no longer needed.

On the other hand, when the device is stopped, for example, when the inverter 11 is cut off due to an electrical load short circuit, the switch 8 is turned on in advance and the dummy resistor 9 is connected to the fuel cell 1.
While connected to the fuel cell, the inverter is disconnected from the fuel cell by narrowing down the control angle of the inverter or by opening the disconnectors 10 and 12. By the way, according to the conventional design concept of dummy resistors,
When the DC current of the inverter or the disconnector 10 is opened, it is no longer necessary to insert the dummy resistor 9 into the circuit. Vessel 9 had been separated.

The present inventors have found that by slightly delaying the disconnection of this dummy resistor, the generation of the above-mentioned differential pressure in the fuel cell can be reduced, and an embodiment will be described below.

The embodiment shown in FIG. 3 is an example using a timer, and when the direct current shown in FIG. The closing relay 24 of the switch 8 is energized to close the dummy resistor 9 first, and the timer 25 is used to delay the contact 2 for a short time.
6 to excite the trip relay 27 of the DC/breaker 10 to open the DC/breaker 10, and after a predetermined time limit, the timer 28 opens the contact 29 to activate the closing relay 24 of the dummy resistor closing switch 8. is demagnetized, and the dummy resistor is disconnected by energizing the dummy resistor closing relay 31 of the dummy resistor input switch 8 via the contact 30. This figure 3 shows an example of the connection in principle, and it goes without saying that it is easy to adopt a different circuit system depending on the configuration of the closing and disconnecting relays, or to make the entire circuit contactless. .

As the dummy resistor 9, a type that includes inductance is often used rather than a pure DC resistor, but as shown in Figure 4, a type that includes a DC resistor (or a series connection of this and an inductance) ) 9a and capacitor 9b in series, the timer 28 in FIG. 3 can be omitted due to the time constant of this dummy resistor.

Also, instead of the single dummy resistor 9, a fifth
As shown in the figure, multiple dummy resistors 9A, 9B,
9C etc., and set the value of each resistor to 1:2:4, for example.
Select as shown below and select the switch 8 with the optimal combination.
A, 8B, 8C, etc. may be selected.

Furthermore, the magnitude of the differential pressure that occurs when the equipment is stopped is
Since it depends on the amount of fuel gas consumed immediately before the stop, and therefore on the magnitude of the load current, the output DC current is detected by the detector 32, as shown in FIG. 6, and the dummy resistor resistance 9C is Either change the value or use the circuit shown in Figure 5 to find a combination suitable for the current value in advance, and then insert a dummy resistor of this combination at the same time as the inverter is turned on or off. It's fit for purpose. In this case, it is also possible to perform selection control of the dummy resistor by detecting the AC output current of the inverter instead of detecting the DC current. Further, when a single dummy resistor shown in FIG. 4 is used, the closing time may be controlled based on the above-mentioned current value. moreover,
It may also be expedient in some cases to additionally control the resistance value or the input time by monitoring the pressure of the reaction gas in the fuel cell. The switch 8 can be replaced with a transistor, thyristor, etc.

As described above, according to the present invention, when the fuel cell power generation device is stopped, the dummy resistor, which would conventionally be disconnected immediately after being turned on, is continuously controlled to be turned on from the viewpoint of limiting the rise in pressure of the reactant gas in the fuel cell. This has the advantage that it is possible to prevent adverse effects on the fuel cell quickly and without adding extra cost, compared to conventional control using fluid equipment.

[Brief explanation of the drawing]

Fig. 1 is a current-voltage characteristic diagram of the fuel cell, Fig. 2 is a circuit connection diagram for explaining the sequence of turning on and off the dummy resistor, and Figs. 3 to 6 show different embodiments of the present invention. It is a partial circuit diagram. 1...Fuel cell, 8...Dummy resistor input switch, 9, 9A, 9B, 9C...Dummy resistor,
11... Inverter, 25, 28... Timer, 3
1... Current detector.

Claims (1)

[Claims] 1. A fuel cell, an inverter that converts the DC output of the fuel cell into an AC output, and a switch connected between the fuel cell and the inverter to suppress the input voltage of the inverter to a predetermined value or less. In the method of operating a fuel cell power generation apparatus, the dummy resistor is provided with a dummy resistor that can be turned on and off when the apparatus is turned on, and the dummy resistor is turned on for a sufficient time to turn on and off the reactant gas when the apparatus is turned off. A method of operating a fuel cell power generation device characterized by: 2. In the method described in claim 1,
1. A method of operating a fuel cell power generation apparatus, characterized in that a dummy resistor is inserted immediately before an electrical load is cut off, and the dummy resistor is cut off after a predetermined period of time has elapsed after the load is cut off. 3. In the method described in claim 2,
1. A method of operating a fuel cell power generation apparatus, wherein the dummy resistor has capacitance, and the predetermined time is determined by a time constant of the dummy resistor. 4. In the method according to any one of claims 1 to 3, the value or closing time of the dummy resistor is selectively controlled based on the current value immediately before the electric load is cut off. Features: How to operate a fuel cell power generation device. 5. The method according to any one of claims 1 to 3, characterized in that the value or closing time of the dummy resistor is selectively controlled based on a change in the reactant gas pressure of the fuel cell. How to operate a fuel cell power generation device. 6. In the method recited in claim 1,
1. A method of operating a fuel cell power generation apparatus, characterized in that a plurality of dummy resistors are prepared, and at least one of the plurality of dummy resistors is selected based on a current value immediately before an electric load is cut off.