Fuel cell system and method for operating fuel cell system

Abstract

A fuel cell system includes a fuel cell, a fuel-gas supplier, a fuel supply path, a shut-off valve, a pressure reducing valve, an auxiliary device, a pressure sensor, a depressurizing device, and a controller. The fuel supply path connects the fuel cell to the fuel-gas supplier. The pressure sensor is configured to detect a pressure in the fuel supply path located downstream of the pressure reducing valve. The depressurizing device is to reduce the pressure in the fuel supply path located downstream of the pressure reducing valve. The controller is configured to control the depressurizing device to reduce the pressure in the fuel supply path located downstream of the pressure reducing valve when the pressure detected by the pressure sensor exceeds a predetermined threshold pressure.

1 . A fuel cell system comprising:
 a fuel cell;   a fuel-gas supplier;   a fuel supply path connecting the fuel cell to the fuel-gas supplier;   a shut-off valve to switch between a supply mode and a shut-off mode for fuel gas supplied toward the fuel supply path from the fuel-gas supplier;   a pressure reducing valve provided in the fuel supply path between the shut-off valve and the fuel cell to reduce a downstream pressure relative to an upstream pressure;   an auxiliary device provided in the fuel supply path between the pressure reducing valve and the fuel cell to activate the fuel cell;   a pressure sensor configured to detect a pressure in the fuel supply path located downstream of the pressure reducing valve;   a depressurizing device to reduce the pressure in the fuel supply path located downstream of the pressure reducing valve; and   a controller configured to control the depressurizing device to reduce the pressure in the fuel supply path located downstream of the pressure reducing valve when the pressure detected by the pressure sensor exceeds a predetermined threshold pressure.   
     
     
         2 . The fuel cell system according to  claim 1 , wherein
 the controller determines whether or not the pressure detected by the pressure sensor exceeds the predetermined threshold pressure when the fuel cell is to be activated.   
     
     
         3 . The fuel cell system according to  claim 2 , wherein
 if the pressure detected by the pressure sensor exceeds the predetermined threshold pressure when the fuel cell is to be activated, the controller controls the depressurizing device to reduce the pressure in the fuel supply path located downstream of the pressure reducing valve to the predetermined threshold pressure or to a pressure lower than the predetermined threshold pressure, and subsequently opens the shut-off valve and actuates the auxiliary device so as to activate the fuel cell.   
     
     
         4 . The fuel cell system according to  claim 1 , wherein
 the depressurizing device comprises a low-pressure open valve provided in the fuel supply path located downstream of the pressure reducing valve, the a low-pressure open valve being to switch the fuel supply path between a state in which the fuel supply path is in communication with a low-pressure area with a pressure lower than the predetermined threshold pressure and a state in which the fuel supply path is shut off from the low-pressure area, and   the controller opens the low-pressure open valve so as to reduce the pressure in the fuel supply path located downstream of the pressure reducing valve, and includes a pressure responsive valve provided in the fuel supply path located downstream of the pressure reducing valve, the pressure responsive valve being to switch from a closed state to an open state when the pressure in the fuel supply path located downstream of the pressure reducing valve exceeds an upper limit pressure set to be higher than the predetermined threshold pressure so as to allow the fuel supply path to communicate with the low-pressure area.   
     
     
         5 . The fuel cell system according to  claim 1 , wherein
 the predetermined threshold pressure is set based on a maximum normal pressure value of the auxiliary device.   
     
     
         6 . A method for operating a fuel cell system that includes a fuel cell, a fuel-gas supplier, a fuel supply path connecting the fuel cell to the fuel-gas supplier, a shut-off valve to switch between a supply mode and a shut-off mode for fuel gas supplied toward the fuel supply path from the fuel-gas supplier, a pressure reducing valve provided in the fuel supply path between the shut-off valve and the fuel cell to reduce a downstream pressure relative to an upstream pressure, and a controller, the method comprising:
 detecting a pressure in the fuel supply path located downstream of the pressure reducing valve using a pressure sensor;   determining whether or not the pressure detected by the pressure sensor exceeds a predetermined threshold pressure; and   reducing the pressure in the fuel supply path located downstream of the pressure reducing valve when the pressure detected by the pressure sensor exceeds the predetermined threshold pressure.   
     
     
         7 . The method according to  claim 6 , wherein
 the predetermined threshold pressure is set based on a maximum normal pressure value of the auxiliary device.