A fuel cell system includes a battery, a fuel cell configured to generate power in accordance with a load, an inverter configured to convert power output from the fuel cell into alternating-current power and supply the alternating-current power to a motor, and a converter configured to control voltage between the inverter and the fuel cell using power output from the battery. The fuel cell system includes a voltage control unit configured to control the converter such that the voltage between the inverter and the fuel cell does not fall below a voltage lower limit of the inverter, and a lower limit voltage control unit configured to, when power required by the motor increases, cause the voltage between the inverter and the fuel cell to fall below the voltage lower limit of the inverter.

A method for stopping a fuel cell system includes supplying a fuel gas containing a fuel to an anode of a fuel cell which is to generate electric power. An oxidant gas containing an oxidant is supplied to a cathode of the fuel cell. A concentration of the oxidant gas in the cathode is reduced. An output voltage of the fuel cell is lowered while a slope of a change in the output voltage with respect to elapsed time is controlled such that an output current of the fuel cell has a predetermined relationship with a predetermined current reference value.

A fuel cell system includes: a fuel cell unit including first to nth fuel cells connected in series to each other to supply electric power to a load device; first to nth supply systems that independently supply cathode gas to the first to nth fuel cells, respectively; a switching device capable of switching a state between a connected state and a disconnected state; and a control unit, when required output to the fuel cell unit is equal to or smaller than a threshold value, configured to control the switching device to switch the state from the connected state to the disconnected state, and to control the first to nth supply systems to respectively control the first to nth fuel cells so as to respectively control flow rates of the cathode gas to be supplied to the first to nth fuel cells.

A redox flow battery system includes a battery cell that performs charge-discharge by supplying an electrolyte; a monitor cell to which the electrolyte is supplied; a voltmeter that measures an open circuit voltage of the monitor cell; a thermometer that measures a liquid temperature of the electrolyte; and a controller that controls the charge-discharge of the battery cell based on the open circuit voltage, and the controller corrects the open circuit voltage in accordance with the liquid temperature.

A fuel cell system for air vehicles, wherein the fuel cell system comprises: a fuel cell, a fuel gas system for supplying fuel gas to the fuel cell, a potential sensor, and a controller; wherein the fuel gas system comprises a fuel gas supplier; wherein the controller determines whether or not a potential of the fuel cell measured by the potential sensor, is a reversal potential; and wherein, when the controller determines that the potential of the fuel cell is a reversal potential, the controller increases a fuel gas supply from the fuel gas supplier to the fuel cell.

A fuel cell system includes: a fuel cell unit including first to nth fuel cells connected in series to each other to supply electric power to a load device; first to nth supply systems that independently supply cathode gas to the first to nth fuel cells, respectively; a switching device capable of switching a state between a connected state and a disconnected state; and a control unit, when required output to the fuel cell unit is equal to or smaller than a threshold value, configured to control the switching device to switch the state from the connected state to the disconnected state, and to control the first to nth supply systems to respectively control the first to nth fuel cells so as to respectively control flow rates of the cathode gas to be supplied to the first to nth fuel cells.

A power supply system includes one or more fuel cell outputs, each including a fuel cell and a voltage converter that converts an output voltage of the fuel cell, a voltage adjuster connected in parallel with the one or more fuel cell outputs to a load, the voltage adjuster including a diode and a regenerative DC power supply, and a control device that controls the one or more fuel cell outputs and the voltage adjuster, wherein the control device performs, after activating the fuel cell, limiting control through the voltage adjuster such that the voltage of each of the one or more fuel cell outputs becomes a target value and starts power supply from the one or more fuel cell outputs to the load when the voltage of each of the one or more fuel cell outputs reaches the target value.

A fuel cell system includes: a fuel cell; a voltage regulator that regulates an output voltage of the fuel cell; and a controller configured to perform a refresh process of decreasing the output voltage of the fuel cell to a reduction voltage at which an oxide film formed on the cathode is reduced, by controlling the voltage regulator. The controller, before the refresh process, calculates a first amount, the first amount being an amount by which the oxide film is to be removed from the cathode. The controller determines, as the output voltage of the fuel cell, a refresh voltage that enables the first amount of the oxide film to be removed within a preset reference time. The controller operates the voltage regulator so as to cause the output voltage of the fuel cell to become the refresh voltage when the refresh process is performed.

A voltage applying unit of a water detecting device applies, to a pair of electrodes, a voltage changing within an application range that includes a first voltage which is smaller than an electrolysis voltage of water and a second voltage which is larger than the electrolysis voltage of the water. A judging unit judges presence or absence of the water based on change in electric current measured by a current measuring unit when the voltage changing within the application range is applied to the pair of electrodes.

A fuel cell power controller tracks load current and fuel cell output voltage, and alerts on excessive fuel cell ramp rate, so another power source can supplement the fuel cell and/or the load can be reduced. A power engineering process makes efficient use of available fuel cell power by ramping up power flow rapidly when power is available, while respecting the ramp rate and other power limitations of the fuel cell and safety limitations of the load. Power flow decreases after an alert indicating an electrical output limitation of the fuel cell. Permitted power flow increases in response to a power demand increase (actual or requested) from the load in the absence of the alert. Power flow may increase or decrease in a fixed amount, a proportional amount, or per a sequence. A power controller relay may trip open on a low fuel cell output voltage or high load current.