Abstract: A system for electrolysis power conversion includes electrolyser cells arranged as controllable series connected cell groups, a unit for electrolysis operation at a first voltage in the range of 1.0-2.5V per cell and a unit for at least intermittently drawing current from the cell groups at a second voltage at 0.4-1.0V per cell. The system includes at least one capacitor bank maintained at the first voltage and a capacitor bank maintained at the second voltage, the capacitor banks and cell groups having one pole in common and a bidirectional non-isolating DC/DC converter for connecting the first and second voltage capacitor banks. The system further includes a controller for the first and second voltages levels and a half-bridge switch pair for each controllable cell group for individually alternating between the first and second voltage levels being applied to the cell groups to prevent escalating unbalances and cell degradation.

Abstract: An object of the invention is a recirculated solid oxide electrolyzer cell system, a cell comprising a fuel side (100), an oxygen rich side (102), and an electrolyte element (104) between the fuel side and the oxygen rich side.

Abstract: A start-up transition process is disclosed for a fuel cell system operation state, which includes utilization of predefined first and second temperature limits for the fuel cells, specifying a low temperature operating state of cells below the first limit, at which presence of carbonaceous species at the cells is precluded, a transition temperature range of cells above the first and below the second limit at which fuel flow supply is initiated to the fuel system in a mixture with air, combined with anode tail gas recirculated at a recirculation rate over 70, and an intermediate temperature operating state of the cells above the second temperature limit, at which free oxygen at the anodes.

Abstract: A control arrangement in a fuel cell system for producing electricity with fuel cells, the fuel cell system including means for recirculating fuel through the anode sides of the fuel cells, and at least one system controller in a control processor for controlling the operation of the fuel cell system. The control arrangement includes means for performing a substantially asynchronous chemical reaction rates calculation process of at least one of fuel composition and fuel flow rate to accomplish information in a substantially iterative process on at least recirculation ratio of the fuel recirculation through anodes and means for generating, in a substantially synchronous process with the system controller process, fuel utilization (FU) information and Carbon formation information by utilizing the latest available recirculation ratio information provided by said asynchronous process.

Abstract: An arrangement for high temperature fuel cell system for substantially reducing the amount of purge gas in an emergency shut-down situation. The arrangement includes a known volume for containing a pneumatic actuation pressure, the known volume including at least one discharge route for designed discharge rate, at least one pressure source providing pressure capable of performing the pneumatic actuation, at least one purge gas source having a gas overpressure capable of displacing residual reactants in the fuel cell system. Purge gas is discharged through the discharge route causing pressure decline in the known volume, accomplishing a designed time delay in state change of at least one pneumatically actuated valve, to reduce or close down completely emergency shutdown actuated flow of the purge gas into the fuel cell system piping after the designed time delay.

Abstract: An offset control arrangement is disclosed for controlling voltage values in a fuel cell system including an anode side, a cathode side and an electrolyte between the anode side and the cathode side. The fuel cell system can include at least one fuel cell array of at least two fuel cells, and at least one load for performing load function. The offset control arrangement can include voltage monitoring for monitoring an input voltage of the load, a control processor for processing the monitoring information, and at least one offsetting source in serial connection to the at least one fuel cell array, with a power level of the offsetting source being substantially low compared to the power level of the fuel cell array, and the offsetting source being arranged to perform at least unidirectional shifting of fuel cell array output voltage.

Abstract: An arrangement is disclosed for reducing use for safety gases in a high temperature fuel cell system, each fuel cell in the fuel cell system including an anode side, a cathode side, and an electrolyte between the anode side and the cathode side. The fuel cells can be arranged in fuel cell stacks. The fuel cell system can include a fuel cell system piping for reactants, and feeding of fuel to the anode sides of the fuel cells. Electrical anode protection can be achieved by supplying a predefined voltage separately to at least two fuel cell stacks or groups of fuel cell stacks to prohibit oxidation of anodes.

Abstract: An arrangement for improved operability of a high temperature fuel cell device at higher fuel cell voltage values than nominal voltage values, each fuel cell in the fuel cell device including an anode side, a cathode side, and an electrolyte between the anode side and the cathode side, and the arrangement includes means for determining temperature information of the fuel cells and main power converter for loading fuels cells at least up to their rated power level.

Abstract: Exemplary embodiments are directed to a fuel cell system that is fed fuel and provided information on the fed fuel. The system generates information about fuel utilization in the fuel cells and oxygen to carbon ratio (O/C ratio) in the fuel cell system process and includes features for controlling a loading of the fuel cells. The fuel cell system also includes a first closed loop controller for controlling the feeding of fuel by taking into account the fuel utilization information as process feedback information, and by implementing a constraint function taking control of O/C ratio by restricting output of the first controller when said O/C ratio deviates from an allowed range, and a second controller for controlling active fuel cell loading by implementing a constraint function taking control of fuel utilization restricting output of the second controller when said fuel utilization deviates from an allowed range.

Abstract: Exemplary systems and methods for adjusting current values in a fuel cell system for producing electricity with fuel cells, include drawing major part of the current from at least one serial connection. An adjusting circuit adjusts current values by drawing or supplying current of at least one stack of individual fuel cell stacks or current of at least one group of the groups of stacks within the serial connection. The adjusting circuit is integrated with the at least one stack of individual fuel cell stacks or with the at least one group of the groups of stacks. Compensation current of the at least one stack or group is a small percentage of a major part of the current in the serial connection of stacks.

Abstract: A method is disclosed for producing electricity in high temperature fuel cell systems. Gas is circulated at anode sides of the fuel cells. A gas composition at anode sides is determined for providing composition information, and desired temperature conditions are arranged for producing electricity with fuel cells. Rated power of the fuel cell system is controlled by an auxiliary water feed to the fuel cell system by utilizing the composition information, by performing controlled gas recirculation at anode sides by utilizing the composition information by changing the gas recirculation, when a desire arises, and by performing controlled gas feed in to the fuel cell system by utilizing the composition information by changing the gas feed, when a need arises, to change the rated power of the fuel cell system to keep electricity production conditions substantially optimal for the gas used as fuel in the high temperature fuel cell system.

Abstract: A method is disclosed for monitoring galvanic isolation of a fuel cell device. At least one stack of fuel cells and at least one load circuit for fuel cells are arranged to an electrically freely floating configuration towards at least one structure near fuel cells. A controlled switching is performed via at least two switching points to at least one measurement element having known impedance in connection to the at least one structure. Measurements are performed from the measurement element to form voltage information. The voltage information and at least voltage information between switching points are processed to check floatages of fuel cells in relation to said at least one structure.

Abstract: A method is disclosed for producing electrical current by a fuel cell device, which inputs electrical current to an electrical network. A fuel cell device can be arranged to be parallel connected to the electrical network. A phase reference signal can be utilized in the inputting of the electrical current, and electrical current inputted to electrical network can be current controlled by a power transformer having a power stage. The fuel cell device can be switched off from the electrical network when a malfunction occurs in the electrical network. The fuel cell device can be changed, using the phase reference signal, to the switched off operation mode for performing voltage controlled operation of the power transformer. A controllable load can be used for maintaining a power stability between the voltage controlled power transformer and other parts of the fuel cell device.

Abstract: The disclosure relates to a system and a method for enhancing the preheating of a fuel cell system having at least one fuel cell unit whose fuel cells are provided with an anode side, a cathode side and an electrolyte provided therebetween, as well as a connecting plate set between each of the fuel cells. In operation, safety gas flowing on the anode side is heated, at least for the most part (e.g., greater than 50%), in the fuel cell unit by thermal energy contained in a gas flowing on the cathode side.