A method for diagnosing the operating state of an electrochemical system in real-time comprising a stack of cells, said method comprising steps for performing voltage measurements of said cells. Said method further comprises: real-time processing of the voltage measurements (61) thus performed, in order to extract specific waveforms (40) therefrom, converting said specific waveforms in order to generate specific points (65) therefrom of the real-time operation of the electrochemical system, and comparing these specific points of the real-time operation and specific points (75) of an off-line operation of the electrochemical system that originate from a conversion of specific waveforms (74) extracted from voltage measurements (78) performed off-line, while the electrochemical system is placed in known operating states including fault states, so as to produce information (69) relating to the real-time operating state of the electrochemical system.

A method for controlling a carbon dioxide utilization in a fuel cell assembly includes: measuring a voltage across the fuel cell assembly; determining an estimated carbon dioxide utilization of the fuel cell assembly based on at least the measured voltage across the fuel cell assembly by determining an expected voltage of the fuel cell assembly based on at least a temperature of the fuel cell assembly, a current density across the fuel cell assembly, a fuel utilization of the fuel cell assembly, and a cathode oxygen utilization of the fuel cell assembly; determining the estimated carbon dioxide utilization based on a comparison between the measured voltage and the determined expected voltage; comparing the determined estimated carbon dioxide utilization to a predetermined threshold utilization; and upon determining that the determined estimated carbon dioxide utilization is higher than the predetermined threshold utilization, reducing the carbon utilization of the fuel cell assembly.

A fuel cell system may include: a fuel cell unit connected to an output terminal; a battery unit connected to the fuel cell unit in parallel: and a controller configured to control the fuel cell unit to maintain an output voltage of the fuel cell unit at an idling voltage which is higher than zero and lower than an output voltage of the battery unit when a target output power is lower than an output power lower limit set for the fuel cell unit.

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.

A method for determining the starting state of a fuel-cell system is provided having cathode and anode chambers separated by a membrane-electrode assembly, comprising the steps of initially introducing hydrogen into the anode chamber, measuring the voltage and evaluating whether at least a threshold value has been reached immediately after the start of the introduction of hydrogen into the anode chamber, and determining the starting state as a function of whether the threshold value has been reached.

To provide a fuel cell system configured to increase fuel cell performance even at high altitude. A fuel cell system for air vehicles, wherein the fuel cell system comprises: a fuel cell, an oxidant gas system for supplying oxidant gas to the fuel cell, an altitude sensor, and a controller; wherein the oxidant gas system comprises an air compressor and a bypass flow path bypassing the fuel cell; wherein the bypass flow path comprises a bypass valve; and wherein, when the controller detects an altitude increase measured by the altitude sensor, the controller increases a rotational speed of the air compressor, and the controller increases an opening degree of the bypass valve.

A system includes a fuel cell engine, a plurality of switching devices, and a controller. The fuel cell engine includes a plurality of fuel cell modules connected in series as a fuel cell string, and then a plurality of these strings connected in parallel. The switching device(s) are electrically coupled to bypass when required each module(s) and or disconnect each string(s). The decision whether a module(s) and/or string(s) are bypassed, disconnected, or left to operate is based on a sensory feedback that is input into the finite state machine and fault management process that are embedded within the fuel cell controller. The bypassing scheme at the module level is handled in a manner such that the remaining modules within a series string can provide continuous, uninterrupted flow of current to the end application.

Disclosed is a method and a device configured to control deterioration avoidance operation of a fuel cell system. In one aspect, the method may include starting the deterioration avoidance operation when an operation of a fuel cell is restarted in a state where an energy storage device is operating, and the fuel cell is stopped; controlling anode hydrogen pressure based on a predetermined condition, the condition indicating that the anode hydrogen pressure needs to be increased; determining hydrogen recirculation and supplying hydrogen including a process to determine whether to recirculate hydrogen based on a predetermined condition, the condition indicating that hydrogen needs to be recirculated, before supplying hydrogen; determining air recirculation and supplying air including a process to determine whether to recirculate air based on a predetermined condition, the condition indicating that air needs to be recirculated, before supplying air; and terminating the deterioration avoidance operation and starting operation of the fuel cell.

A fuel cell system includes a fuel cell stack and a control device. The control device raises the voltage of the fuel cell stack until a predetermined voltage condition is met, by supplying a cathode with an oxidant gas before current sweep is started when the fuel cell system is started and a value measured by a temperature sensor is equal to or less than a temperature determined in advance. The control device executes stand-by control, in which a current command value is kept constant, when a measured voltage value reaches a control start voltage value smaller than a voltage command value in a transition period, and ends the stand-by control by permitting a change in the current command value when the measured voltage value reaches a permission voltage value equal to or more than the voltage command value during execution of the stand-by control.

This specification describes a system and method for controlling the voltage produced by a fuel cell. The system involves providing a bypass line between an air exhaust from the fuel cell and an air inlet of the fuel cell. At least one controllable device is configured to allow the flow rate through the bypass line to be altered. A controller is provided to control the controllable device. The method involves varying the rate of recirculation of air exhaust to air inlet so as to provide a desired change in fuel cell voltage.