A fuel cell system that includes a first fuel cell that generates electric power using a hydrogen-containing fuel gas; a second fuel cell that generates electric power using off-gas exhausted from the first fuel cell and containing hydrogen that has not reacted in the first fuel cell; a first control device that controls the electric power output from the first fuel cell by adjusting a current or a voltage being output from the first fuel cell; a second control device that controls the electric power output from the second fuel cell by adjusting a current or a voltage being output from the second fuel cell; and an output control device that controls at least one of the first control device or the second control device such that a total electric power being generated by the first fuel cell and the second fuel cell approaches an electric power demand.

The invention relates to a supply circuit of the cathode (250) of at least one electrochemical cell (200) of the PEMFC type, which further comprises a membrane (290) separating an anode (210) and said cathode (250), with this circuit comprising: a supply channel (220) comprising an inlet (282) and making it possible to convey a fluid (90) in contact with the cathode (250); a discharge channel (280) that makes it possible to remove gases from the cell, a recirculation channel (100, 100), comprising: a first opening (102) connected to the outlet (284) of the discharge channel (280); a second opening (104) connected to the inlet (282) of the supply channel (280), by the intermediary of a connector (80); a third opening (106) and means for removing (140) that allow at least one portion of the fluid (90) to be removed from the recirculation channel by the third opening (106), the recirculation channel (100, 100) and/or the supply channel further comprising at least one compressor (C1, C2), which makes it possible to control the flow rates and/or the proportion of the fluids to be mixed in the connector.

The disclosure relates to a method for operating a fuel cell that comprises at least one individual cell with a membrane and catalysts, wherein humidity within the fuel cell is actively influenced as a function of a voltage of the fuel cell, and the method further includes specifying an initial humidity at an initial operating-point-related voltage, and specifying a second humidity that is lower than the first humidity at a second operating-point-related voltage that is higher than the first operating-point-related voltage. Furthermore, the disclosure relates to a fuel cell system that is configured to perform the method according to the disclosure.

A control device is configured to control a first boost converter and a second boost converter. The control device is configured such that, when a prescribed state where an output of the second boost converter cannot be made at a ratio of an output voltage to an input voltage in the second boost converter to be equal to or more than a predetermined value is detected, the control device calculates a target output voltage of a fuel cell by using an voltage on an input side or an output side of the second boost converter measured by a measuring portion and a first value which is equal to or larger than a minimum boost ratio of the first boost converter, and controls the fuel cell so that an output voltage of the fuel cell is equal to or lower than the target output voltage.

A fuel cell system includes: a fuel cell including a fuel gas passage through which a fuel gas flows and an oxidant gas passage through which an oxidant gas flows, an inlet of the fuel gas passage being located closer to an outlet of the oxidant gas passage than to an inlet of the oxidant gas passage, an outlet of the fuel gas passage being located closer to the inlet of the oxidant gas passage than to the outlet of the oxidant gas passage; an oxidant gas supply unit supplying the oxidant gas to the fuel cell; and a supply amount controller configured to control the oxidant gas supply unit, the supply amount controller is configured to control the oxidant gas supply unit so that a stoichiometric ratio of the oxidant gas in a high-temperature high output power state is greater than that in a high-temperature low output power state.

A control unit of an aging apparatus performs a first pattern of supplying a humidified H.sub.2 gas to an anode and supplying a humidified N.sub.2 gas to a cathode, to thereby move protons from the anode to the cathode through an electrolyte membrane. Further, the control unit performs a second pattern of supplying the humidified N.sub.2 gas to the anode and supplying the humidified H.sub.2 gas to the cathode, to thereby move protons from the cathode to the anode through the electrolyte membrane.

Methods and apparatus for detecting electrical short circuits in fuel cell stacks are provided. The methods involve supplying a reactant and an inert gas to a fuel cell stack and measuring the open circuit voltage of fuel cell assemblies in the fuel cell stack. The sensitivity of the methods can be adjusted to detect an electrical short circuit having a resistance at or below a particular threshold short-circuit resistance value, by using a suitable reactant concentration in the method. The methods can include determining a set-point reactant concentration that can be used to detect an electrical short circuit having a resistance at or below a particular threshold short-circuit resistance value.

A fuel cell system comprises a fuel cell, a switch control module and at least two switch modules; the switch modules each is coupled to a positive electrode and a negative electrode of the fuel cell, and comprises switch units; the switch units each comprises a switch; the switch comprises a control terminal, a current input terminal and a current output terminal; in at least one of the at least two switch modules, the switch unit further comprises a voltage division structure; the voltage division structure is coupled in series between the current input terminal and the positive electrode of the fuel cell, or, the voltage division structure is coupled in series between the current output terminal and the negative electrode of the fuel cell; the switch control module is respectively coupled to the control terminals of the switches of the at least two switch modules to respectively control on-off of the switches.

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 fuel cell system comprises a fuel cell; a fuel cell controlling converter; an oxidizing gas supplier that is configured to supply an oxidizing gas to the fuel cell; and a controller that is configured to control a voltage and a current value of the fuel cell. In a first power generation state, the controller sets the voltage and the current value of the fuel cell according to a required output, based on a current-voltage characteristic of the fuel cell. In a second power generation state, the controller sets the voltage and the current value of the fuel cell according to the required output and a required amount of heat, to a voltage and a current value that provide a lower power generation efficiency than a power generation efficiency in the first power generation state. The controller reduces the required amount of heat in a process of changing over a power generation state from the second power generation state to the first power generation state. The controller reduces a decrement in the required amount of heat per unit time when the required output is equal to or higher than a reference value, compared with a decrement when the required output is lower than the reference value.