Abstract: A fuel cell system includes a plurality of electrical components that are supplied with electric power generated by a fuel cell, a refrigerant circuit that cools the fuel cell using a refrigerant, a tank that is connected to the refrigerant circuit, stores the refrigerant, and is replenished with the refrigerant, a detecting unit that detects an insulation resistance value of the fuel cell system, and an identification unit that identifies at what position of the fuel cell system the insulation resistance value has decreased when it is detected that the insulation resistance value has decreased. The detecting unit performs a process of determining whether the decrease in insulation resistance value is temporary when the identified position is the fuel cell and determines that there is no failure requiring repair when the decrease in insulation resistance value is temporary.

Abstract: A fuel cell system, including: an electric power generation control unit; an insulation-resistance measurement signal generation unit configured to generate a voltage-divided AC signal obtained by dividing an amplitude of a measurement AC signal; and an insulation resistance measurement unit configured to measure a resistance value of the insulation resistance, in which when the insulation resistance measurement unit detects, in a state where a voltage is maintained during an intermittent operation of the electric power generation control unit, an excessive noise state indicating a change in which a range of fluctuations of the peak value of the voltage-divided AC signal exceeds a predetermined allowable range of fluctuations, the insulation resistance measurement unit instructs the electric power generation control unit to change a fluctuation frequency of an output voltage of the fuel cell from a current frequency and then measures the resistance value of the insulation resistance.

Abstract: When reduction of insulation resistance is detected, an FC positive side relay is opened, and a switching element is turned OFF. When the insulation resistance has returned to a normal value as a result of the relay opening and the switching element turning OFF, it is identified that the power leakage is occurring in the area between the positive side relay and the diode.

Abstract: A fuel cell system, including: an electric power generation control unit; an insulation-resistance measurement signal generation unit configured to generate a voltage-divided AC signal obtained by dividing an amplitude of a measurement AC signal; and an insulation resistance measurement unit configured to measure a resistance value of the insulation resistance, in which when the insulation resistance measurement unit detects, in a state where a voltage is maintained during an intermittent operation of the electric power generation control unit, an excessive noise state indicating a change in which a range of fluctuations of the peak value of the voltage-divided AC signal exceeds a predetermined allowable range of fluctuations, the insulation resistance measurement unit instructs the electric power generation control unit to change a fluctuation frequency of an output voltage of the fuel cell from a current frequency and then measures the resistance value of the insulation resistance.

Abstract: A fuel cell system includes: a converter that boosts a voltage input from a fuel cell; a voltage control device that can control a voltage input from an electricity storage unit; a drive circuit that converts direct-current electricity input from the converter and the voltage control device into alternating-current electricity and outputs the converted electricity to the load; a relay that switches between a connected state in which the fuel cell and the drive circuit are connected to each other and a disconnected state in which they are disconnected from each other; and a controller that determines whether the relay is welded by different determination methods using an index current value between the relay and the fuel cell and a first index voltage value between the relay and the converter when the fuel cell system is to be stopped.

Abstract: A fuel cell system includes a plurality of electrical components that are supplied with electric power generated by a fuel cell, a refrigerant circuit that cools the fuel cell using a refrigerant, a tank that is connected to the refrigerant circuit, stores the refrigerant, and is replenished with the refrigerant, a detecting unit that detects an insulation resistance value of the fuel cell system, and an identification unit that identifies at what position of the fuel cell system the insulation resistance value has decreased when it is detected that the insulation resistance value has decreased. The detecting unit performs a process of determining whether the decrease in insulation resistance value is temporary when the identified position is the fuel cell and determines that there is no failure requiring repair when the decrease in insulation resistance value is temporary.

Abstract: A fuel cell system includes: a converter that boosts a voltage input from a fuel cell; a voltage control device that can control a voltage input from an electricity storage unit; a drive circuit that converts direct-current electricity input from the converter and the voltage control device into alternating-current electricity and outputs the converted electricity to the load; a relay that switches between a connected state in which the fuel cell and the drive circuit are connected to each other and a disconnected state in which they are disconnected from each other; and a controller that determines whether the relay is welded by different determination methods using an index current value between the relay and the fuel cell and a first index voltage value between the relay and the converter when the fuel cell system is to be stopped.

Abstract: When reduction of insulation resistance is detected, an FC positive side relay is opened, and a switching element is turned OFF. When the insulation resistance has returned to a normal value as a result of the relay opening and the switching element turning OFF, it is identified that the power leakage is occurring in the area between the positive side relay and the diode.