Introduced is an fuel cell power net including a fuel cell configured to generate power through a reaction between a fuel gas and an oxidizing gas, a power storage device configured to be charged with power generated by the fuel cell or discharged to supply power, a main line configured to electrically connect the fuel cell and the power storage device to each other; a main relay disposed on the main line so as to break or make an electrical connection between the fuel cell and the power storage device, a bypass line which is branched from the main line, bypasses the main relay, and is connected to the power storage device, a bypass relay disposed on the bypass line so as to break or make an electrical connection of the bypass line, and a controller configured to control the main relay or the bypass relay such that the power stored in the storage device is supplied to the fuel cell while the power generation of the fuel cell is stopped.

A fuel cell stack includes a cell stack body including a plurality of stacked power generation cells together. A metal plate and an elastic seal member are overlapped with each other at a position facing a bead seal formed on an end metal separator. A support member includes a recess accommodating the metal plate. A gap is provided between an inner peripheral end of the metal plate and the recess, or between an outer peripheral end of the metal plate and the recess, for absorbing thermal expansion difference between the metal plate and the support member.

A fuel cell system includes a fuel cell stack made by stacking a plurality of cells and configured to generate power by being supplied with fuel gas and oxidation gas, a high-voltage battery configured to supplement the power generated by the fuel cell stack while being charged with the power generated by the fuel cell stack or being discharged, a converter provided between the fuel cell stack and the high-voltage battery and configured to change an output voltage or an output current of the fuel cell stack, a power control unit configured to control the fuel cell stack to generate power when the fuel cell stack is requested to be diagnosed, the power control unit being configured to adjust the output current of the fuel cell stack to a predetermined current, and a voltage sensing unit configured to sense a voltage of the fuel cell stack or voltages of the plurality of cells included in the fuel cell stack in the state in which the output current of the fuel cell stack is the predetermined current.

A power net system of a fuel cell and a method for controlling the same are provided. The power net system includes: a fuel cell to generate electric power through a reaction of a fuel gas and an oxidation gas; batteries to be charged by the electric power generated by the fuel cell or discharged to supply electric power; main lines electrically connecting the fuel cell and the batteries; main relays provided in the main lines to open or allow electrical connections between the fuel cell and the batteries; COD lines branched from the main lines between the fuel cell and the main relays and provided with a COD device to consume input electric power; COD relays provided in the COD lines to open or allow electrical connections to the COD device through the COD lines; and a controller to control the main relays or the COD relays to supply electric power charged in the batteries to the fuel cell.

When a time point of occurrence of a stop state of a fuel cell system is predicted during traveling, a drying state control that causes a fuel cell stack to transition to a dry state is started a predetermined time (a required drying time) before the predicted time point of occurrence of the stop state.

An ECU of a fuel cell vehicle determines whether the vehicle travels on an uphill road or not. When determining that the vehicle travels on the uphill road, the ECU performs at least one of a temperature reduction control for reducing the temperature of a fuel cell stack and a humidification control for increasing the water content of the fuel cell stack, by the time the vehicle reaches the uphill road.

A fuel cell system includes a controller that controls an amount of air flow to be supplied from an air blower included in an oxygen-containing gas supply to a cell stack to cause a power level (in amperes) of a fuel cell controllable by a power level regulator (power conditioner) and an air utilization to have an increase-control section in which the air utilization increases in accordance with an increase in the power level of the fuel cell and a decrease-control section in which the air utilization decreases in accordance with an increase in the power level. The air utilization is a ratio of an air amount used by the fuel cell for power generation to an oxygen-containing gas (air) amount supplied to the fuel cell.

An FCV includes an FC system and a battery. The FC system includes an FC stack and a boost converter that adjusts output from the FC stack. An FDC-ECU controls the boost converter to adjust an SOC of the battery to a target SOC while electric power is supplied from the FC stack to an inverter. Then, the FDC-ECU lowers the target SOC with decrease in remaining amount of hydrogen in a hydrogen tank.

Disclosed are a grid-connected power conversion system and a control method thereof. The grid-connected power conversion system includes a fuel cell stack generating a DC voltage, a power conversion system (PCS) converting the DC voltage supplied from the stack into an AC voltage, a multi-input transformer including a primary coil having a plurality of voltage input terminals and a secondary coil transforming a magnitude of the voltage applied to the primary coil and outputting the transformed voltage, the plurality of voltage input terminals determining the number of turns of the primary coil differently from each other, one of the plurality of voltage input terminals receiving the AC voltage converted in the PCS, and a controller selecting the one of the plurality of voltage input terminals of the multi-input transformer based on the magnitude of the DC voltage generated from the stack and determining whether to replace the stack.

A method of operating a redox flow battery string including at least first and second redox flow batteries and an outside power source includes: providing a least first and second redox flow batteries in a string electrically connected in a string, and each redox flow battery having a state-or-charge (SOC); obtaining an SOC value for each redox flow battery in the string; identifying a target SOC value in the string; and adjusting the SOC value for at least one of the first and second redox flow batteries to correspond to the target SOC value.