A fuel cell system includes: a wetness target value calculating unit configured to calculate a target value of a wet state of the fuel cell; a gas required flow rate calculating unit configured to calculate a cathode gas required flow rate on the basis of a power generation request to the fuel cell; a wetness-control anode gas flow rate calculating unit configured to calculate a wetness-control anode gas circulation flow rate at least on the basis of the wetness target value and the cathode gas required flow rate during a dry control; an anode gas flow rate control unit configured to control an anode gas circulation flow rate on the basis of the wetness-control anode gas circulation flow rate; a wetness-control cathode gas flow rate calculating unit configured to calculate a wetness-control cathode gas flow rate at least on the basis of the wetness target value and a measured value or estimated value of the anode gas circulation flow rate during the dry control; and a cathode gas flow rate control unit configured to control a cathode gas flow rate on the basis of the cathode gas required flow rate and the wetness-control cathode gas flow rate.

A control method for fuel cell system capable of executing an idle stop operation is provided, in which operation power generation of a fuel cell is selectively stopped according to a required output of a load and cathode gas is intermittently supplied to the fuel cell during an operation stop. An upper limit value and a lower limit value of an output voltage of the fuel cell during the idle stop operation is set, the cathode gas is intermittently supplied with the output voltage of the fuel cell set at a value between the upper limit value and the lower limit value, a wet/dry state of the fuel cell is detected, a wet/dry appropriate range in which the wet/dry state of the fuel cell during the idle stop operation is appropriate is set, and it is determined whether or not the detected wet/dry state of the fuel cell is within the set wet/dry appropriate range. If the wet/dry state of the fuel cell is determined to be outside the set wet/dry appropriate range, the output voltage of the fuel cell is reset, and the cathode gas is intermittently supplied with the output voltage of the fuel cell set at a value between the upper limit value and lower limit value of the reset output voltage.

A state detection device for fuel cell includes a supposed high-frequency impedance value setting unit configured to set a supposed high-frequency impedance value on the basis of an impedance measurement value belonging to an arc region of an impedance curve of the fuel cell, an actually measured high-frequency impedance value calculation unit configured to obtain an actually measured high-frequency impedance value on the basis of an impedance measurement value belonging to a non-arc region of the impedance curve of the fuel cell, and an ionomer resistance estimation unit configured to estimate a value obtained by subtracting the actually measured high-frequency impedance value from the supposed high-frequency impedance value as an ionomer resistance value. The supposed high-frequency impedance value setting unit sets a value of an intersection of an equivalent circuit impedance curve set on the basis of the impedance measurement value belonging to the arc region and a real ads as the supposed high-frequency impedance value.

A system includes a fuel cell stack (FCS) and a controller. The controller is configured to, in response to a stack current request corresponding to a stack current of the FCS which would cause a membrane hydration level of the FCS to be outside of a desired hydration range, adjust the stack current request to correspond to an adjusted stack current of the FCS which causes the membrane hydration level to be maintained within the desired hydration range.

A fuel cell separator, a fuel cell stack having the fuel cell separator, and a reactant gas control method of the fuel cell stack are provided. That is, even when the fuel cell stack operates under the low load operation condition, a reactant gas is supplied to the reactant gas passages of the fuel cell separator, and thus, the length of the passage can be shortened by 50% as compared with the prior art having only one reactant gas passage. Therefore, the reactant gas can be effectively supplied without experiencing pressure loss. Further, in the high load operation of the fuel cell stack, the reactant gas is introduced into the first reactant gas passage of the fuel cell separator and utilized in half of the whole electrode area. Subsequently, the reactant gas is introduced into the second reactant gas passage and utilized in the remaining half of the electrode area. The flow rate of the reactant gas flowing along the passage channels is increased by two times, even when the reactant gas utilizing rate is identical as compared with the reactant gas flow in the low load operation. As a result, the moisture existing in the passage channels can be more effectively discharged and the flooding phenomenon occurring in the high load operation can be prevented. By controlling the reactant gas supply in accordance with an operation condition of the fuel cell stack without experiencing pressure loss and deterioration of the utilizing rate, the flooding phenomenon and concentration polarization phenomenon that occur in the fuel cell stack can be prevented.

A control device of fuel cell system includes an anode gas circulation flow rate control unit configured to control the anode gas circulation flow rate on the basis of the wet/dry state of the electrolyte membrane detected by the wet/dry state detecting unit, a priority setting unit configured to set priority levels of a normal manipulation to a plurality of physical quantities manipulated by the wet/dry state control unit, and the anode gas circulation flow rate control unit includes an anode gas circulation flow rate limiting unit configured to limit a change rate per unit time of the anode gas circulation flow rate during a transient operation for changing the wet/dry state of the electrolyte membrane, and a control quantity compensating unit configured to, if the change rate is limited, compensate an insufficiency in a control quantity of the wet/dry state due to the limitation of the anode gas circulation flow rate, the compensation being carried out by manipulating a physical quantity with a lower priority level of the normal manipulation than a priority level of the normal manipulation of the anode gas circulation flow rate set by the priority setting unit.

A fuel cell system includes: a low-frequency superimposition section superimposing a the low-frequency signal on a fuel cell; and an impedance computation section configured to compute low-frequency impedance of the fuel cell at a time when the low-frequency superimposition section superimposes the low-frequency signal on the fuel cell. The fuel cell system includes: a diagnosing section diagnosing a degree of dryness inside the fuel cell on the basis of low-frequency impedance; and an oxidant gas amount adjustment section configured to adjust an amount of oxidant gas in the fuel cell. The diagnosing section is configured to diagnose the degree of dryness inside the fuel cell on the basis of the low-frequency impedance when the oxidant gas amount adjustment section adjusts the amount of the oxidant gas to be equal to or smaller than a reference gas amount.

A fuel cell system includes a fuel cell for generating electrical power upon being supplied with anode gas and cathode gas. The fuel cell system includes a wetness control state determination unit that determines whether or not a wetness control of controlling a degree of wetness of an electrolyte membrane of the fuel cell is normally executed, a combined capacitance calculation unit that calculates a combined capacitance of the fuel cell, and an anode gas concentration control unit that determines the occurrence of decrease in an anode gas concentration in the fuel cell or executes a control for increasing the anode gas concentration if the combined capacitance of the fuel cell is smaller than a predetermined value when the wetness control is determined to be normally executed.

A method for observing a state of an electrochemical system including a fuel cell including the following steps: measuring parameters that are representative of the fuel cell in operation; forming a control vector; forming a measurement vector; calculating a temporal variation, referred to as a non-corrected temporal variation; calculating a corrective term in sliding mode; calculating an estimate of the state of the electrochemical system; reiterating above steps while incrementing the measurement time.

A fuel cell system includes a fuel supply unit that supplies a fuel to electrolyte membrane of fuel cell, an oxidant supply unit that supplies an oxidant to the electrolyte membrane, and an electricity generation control unit that controls electricity generation by the fuel cell by controlling supply of the oxidant by the oxidant supply unit and supply of the fuel by the fuel supply unit. the fuel cell system includes a wet/dry state detection unit configured to detect a wet/dry state of the electrolyte membrane, a flow rate adjustment unit configured to adjust a flow rate of the fuel supplied to the fuel cell by the fuel supply unit; and a temperature adjustment unit configured to adjust a temperature of the oxidant supplied to the fuel cell by the oxidant supply unit. when reducing an amount of water in the electrolyte membrane in accordance with a signal output from the wet/dry state detection unit, the electricity generation control unit is configured to reduce the flow rate of the fuel, and increase the temperature of the oxidant in accordance with the signal from the wet/dry state detection unit, compared with when increasing the amount of water in the electrolyte membrane.