A system for maintaining insulation resistance of a fuel cell includes a fuel cell stack, a coolant line that allows coolant to pass through the fuel cell stack, a circulation pump that circulates the coolant in the coolant line, a deionizer that removes impurities or ions from the coolant in the coolant line, and a controller configured to measure the insulation resistance of a high-voltage terminal connected to the fuel cell stack, to determine whether recovery control is necessary based on the measured insulation resistance, and upon determining that recovery control is necessary, to control the circulation pump so as to change the flow of the coolant passing through the deionizer.

A fuel cell system includes a fuel cell stack of a plurality of power generation cells and an impedance measuring device for measuring the impedance in the fuel cell stack. When stopping the operation of the fuel cell system, a method for stopping the operation of the fuel cell system operates the plurality of power generation cells to generate electric power, until the impedance value becomes equal to or greater than an objective impedance value. After the impedance value has become equal to or greater than the objective impedance value, the operation stopping method still continues the power generation of the multiple power generation cells for a given period of time.

A method for calculating voltage loss of a fuel cell is provided. The method includes sensing an open circuit voltage that is generated in a stack when the switch is opened and detecting an operation voltage and an operation current that are generated in the stack when the switch is closed. A first change graph of voltage data over time is calculated using the voltage data and current data from a time when the switch is opened in a state where the switch is closed. A first voltage of a point at which a trend line for an interval where the voltage data linearly varies with the time meets the first change graph is sensed and then an ohmic resistance voltage loss is calculated using a difference between the first voltage and the operation voltage.

A system for capturing carbon dioxide in flue gas includes a fuel cell assembly including at least one fuel cell including a cathode portion configured to receive, as cathode inlet gas, the flue gas generated by the flue gas generating device or a derivative thereof, and to output cathode exhaust gas and an anode portion configure to receive an anode inlet gas and to output anode exhaust gas, a fuel cell assembly voltage monitor configured to measure a voltage across the fuel cell assembly, and a controller configured to receive the measured voltage across the fuel cell assembly from the fuel cell assembly voltage monitor, determine an estimated carbon dioxide utilization of the fuel cell assembly based on the measured voltage across the fuel cell assembly, and reduce the carbon dioxide utilization of the fuel cell assembly when the determined estimated carbon dioxide utilization is above a predetermined threshold utilization.

A method for accurately measuring the impedance of the fuel cell stack in the vehicle during operation of the vehicle includes determining whether measuring the impedance of the fuel cell stack is requested during driving of the vehicle driven by using a power of a fuel cell stack, switching a DC-DC converter connecting the fuel cell stack and a battery to each other to a buck mode when measuring the impedance is requested, thereby blocking output current of the fuel cell stack from flowing to the battery through the DC-DC converter, determining a first current value of the fuel cell stack for measuring the impedance, controlling a resistance value of a COD variable resistor consuming the output current of the fuel cell stack according to the first current value, and measuring the impedance of the fuel cell stack while the output current of the fuel cell stack is maintained at the first current value.

In a fuel cell state determination method for determining an internal state of a fuel cell supplied with an anode gas and a cathode gas to generate electricity, a decrease of a reaction resistance value of the cathode caused by hydrogen evolution reaction generated in the cathode as the fuel cell has an oxygen deficiency state is detected, and the oxygen deficiency state is determined on the basis of detection of the decrease of the reaction resistance value.

A control apparatus for a vehicle plant, which is capable of reducing computational load and a storage capacity in a case where the vehicle plant is controlled using a plurality of periodic function values having a plurality of frequencies different from each other. A control apparatus for a fuel cell device includes a first ECU and a second ECU. The second ECU calculates superposition sine wave value of one of frequencies Z to nZ (Hz) based on a frequency command value by a thinning method using a data group of one set of reference sine wave values, stored in a map. The second ECU executes an AC superposition control using the superposition sine wave value, and calculates impedance of the fuel cell device during execution of the AC superposition control. The first ECU executes fuel cell (FC) humidification control process such that the impedance becomes equal to a target value.

A fuel cell reversal event is diagnosed by integrating current density via a controller in response to determine an accumulated charge density. The controller executes a control action when the accumulated charge density exceeds a threshold, including recording a diagnostic code indicative of event severity. The control action may include continuing stack operation at reduced power capability when the accumulated charge density exceeds a first threshold and shutting off the stack when the accumulated charge density exceeds a higher second threshold. The event may be detected by calculating a voltage difference between an average and a minimum cell voltage, and then determining if the difference exceeds a voltage difference threshold. The charge density thresholds may be adjusted based on age, state of health, and/or temperature of the fuel cell or stack. A fuel cell system includes the stack and controller.

A control method for a fuel cell system that includes a solid oxide fuel cell configured to generate power upon receipt of supply of an anode gas and a cathode gas includes an anode protection execution determination process of performing execution determination of an anode protection process of applying a predetermined protection current to the fuel cell in order to restrain catalyst oxidation in an anode of the fuel cell. In the anode protection execution determination process, an internal impedance of the fuel cell at an anode response frequency at which an anode reaction resistance of the fuel cell is detectable is acquired, and based on the internal impedance at the anode response frequency, whether the anode protection process is to be executed or not is determined.

A method for calculating voltage loss of a fuel cell is provided. The method includes sensing an open circuit voltage that is generated in a stack when the switch is opened and detecting an operation voltage and an operation current that are generated in the stack when the switch is closed. A first change graph of voltage data over time is calculated using the voltage data and current data from a time when the switch is opened in a state where the switch is closed. A first voltage of a point at which a trend line for an interval where the voltage data linearly varies with the time meets the first change graph is sensed and then an ohmic resistance voltage loss is calculated using a difference between the first voltage and the operation voltage.