A method of controlling a fuel cell includes collecting, by a control unit, environmental information and state information of a fuel cell stack; determining, by the control unit, a motor output offset value from the collected environmental information and the collected state information of the fuel cell stack; correcting, by the control unit, a default critical output corresponding to a current vehicle operating state based on the determined motor output offset value; determining, by the control unit, the stop or the restart of the fuel cell by comparing a motor output demand determined from current vehicle operating information with the corrected critical output; and controlling, by the control unit, an operating state of the fuel cell to become a state of the determined stop or restart.

A method of controlling a fuel cell includes collecting, by a control unit, environmental information and state information of a fuel cell stack; determining, by the control unit, a motor output offset value from the collected environmental information and the collected state information of the fuel cell stack; correcting, by the control unit, a default critical output corresponding to a current vehicle operating state based on the determined motor output offset value; determining, by the control unit, the stop or the restart of the fuel cell by comparing a motor output demand determined from current vehicle operating information with the corrected critical output; and controlling, by the control unit, an operating state of the fuel cell to become a state of the determined stop or restart.

System for recirculating hydrogen in a fuel cell including a tank having an inlet connectable to an outlet of the fuel cell and an outlet connectable to a line for feeding hydrogen to the fuel cell; the recirculation system includes a first check valve and a second check valve; the first check valve can be inserted between the outlet of the fuel cell and the inlet of the tank, for adjusting a flow from the fuel cell to the tank whilst the second check valve can be inserted between the outlet of the tank and the hydrogen feed line, for adjusting a flow of hydrogen from the tank to the feed line.

System for recirculating hydrogen in a fuel cell including a tank having an inlet connectable to an outlet of the fuel cell and an outlet connectable to a line for feeding hydrogen to the fuel cell; the recirculation system includes a first check valve and a second check valve; the first check valve can be inserted between the outlet of the fuel cell and the inlet of the tank, for adjusting a flow from the fuel cell to the tank whilst the second check valve can be inserted between the outlet of the tank and the hydrogen feed line, for adjusting a flow of hydrogen from the tank to the feed line.

A system for operating a fuel cell includes a controller configured to derive an output limit value of the fuel cell through an interval average value corresponding to an average of output values of the fuel cell for a designated time and a cumulative average value corresponding to an average of the output values of the fuel cell until the current point in time after starting to operate the fuel cell, and to control operation of the fuel cell based on the derived output limit value.

Disclosed is a unitized regenerative fuel cell system, comprised of a unitized regenerative fuel cell able to operate in a fuel cell mode for electric power generation and in a water electrolysis mode for hydrogen and oxygen production, and a plurality of fire-detecting sensors for detecting fire in each zone of a tunnel, and configured to supply oxygen to zones wherein fire has not occurred if occurrence of fire has been detected in a tunnel, and a method for controlling the same.

The present disclosure generally relates to systems and methods for managing and/or excess hydrogen flow in a system comprising a fuel cell or fuel cell stack based on humidity measurements.

A braking control unit of a fuel cell vehicle is configured to, in a period during which the fuel cell vehicle is being braked in response to a braking request, (i) when an estimated amount of stagnant water is less than a predetermined second water amount less than a first water amount, limit an upper limit electric power of a regenerated electric power resulting from regenerative operation to a predetermined first value or below, and (ii) when the estimated amount of stagnant water is greater than or equal to the second water amount, execute an upper limit changing process of setting an upper limit electric power to a second value lower by a predetermined value than the first value.

A braking control unit of a fuel cell vehicle is configured to, in a period during which the fuel cell vehicle is being braked in response to a braking request, (i) when an estimated amount of stagnant water is less than a predetermined second water amount less than a first water amount, limit an upper limit electric power of a regenerated electric power resulting from regenerative operation to a predetermined first value or below, and (ii) when the estimated amount of stagnant water is greater than or equal to the second water amount, execute an upper limit changing process of setting an upper limit electric power to a second value lower by a predetermined value than the first value.

An apparatus for estimating an amount of condensed water in an anode of a fuel cell system includes: an initial anode water vapor amount calculation unit to calculate an initial amount of water vapor in the anode of a fuel cell upon startup, an anode diffusion amount calculation unit to calculate an amount of H.sub.2O diffused from a cathode to the anode, a purge amount calculation unit to calculate an amount of water vapor discharged upon gas purging in the anode, a recirculation amount calculation unit to calculate the amount of water vapor recirculated to the anode, and a condensed water amount determination and water level estimation unit to calculate the actual amount of water vapor in the anode based on values calculated using these units and to calculate the amount of condensed water in a water trap.