Abstract: A method for operating a fuel cell power plant to supply power to an internal load and an external load, includes the steps of evaluating power needs of the internal and external loads to determine a fixed IDC value sufficient to supply the needs; providing auxiliary power to the internal load and output power to the external load so as to maintain operation of the fuel cell power plant at the fixed IDC value; and adjusting at least one of the auxiliary power to the internal load and output power to the external load so as to maintain operation of the fuel cell power plant at the fixed IDC value. Operation within a preselected voltage range is also provided.

Abstract: An auxiliary load (148) for a fuel cell stack (102) is alternatively connected and disconnected from the fuel cell external circuit (177, 178) by a switch (200) in response to a switch control (201), repetitively, during startup and shutdown. The switch may be an insulated gate bipolar transistor (208) which is turned on and off by hunting between an upper limit voltage (207) and a lower limit voltage (208), which may be performed by compare circuits (205, 206), by the controller (202), or by commercially available voltage responsive hysteresis switches. Schedules of duty cycle as a function of cell stack voltage for startup (212) and shutdown (213) control a pulse width modulator (215) which operates the switch. Controls (229, 231) may limit the modulation so that the auxiliary load does not overheat, in response to temperature (221) of the load or a voltage/power model (235). The auxiliary load may comprise a heater in a water accumulator (247), an air intake (257) or an enthalpy recovery device (262).

Abstract: A method for operating a fuel cell power plant to supply power to an internal load and an external load, includes the steps of evaluating power needs of the internal and external loads to determine a fixed IDC value sufficient to supply the needs; providing auxiliary power to the internal load and output power to the external load so as to maintain operation of the fuel cell power plant at the fixed IDC value; and adjusting at least one of the auxiliary power to the internal load and output power to the external load so as to maintain operation of the fuel cell power plant at the fixed IDC value.

Abstract: A method for operating a fuel cell power plant to supply power to an internal load and an external load, includes the steps of evaluating power needs of the internal and external loads to determine a fixed IDC value sufficient to supply the needs; providing auxiliary power to the internal load and output power to the external load so as to maintain operation of the fuel cell power plant at the fixed IDC value; and adjusting at least one of the auxiliary power to the internal load and output power to the external load so as to maintain operation of the fuel cell power plant at the fixed IDC value.

Abstract: A control system and method for controlling a fuel processing system operational to produce a gas for a downstream process from a fuel, wherein the fuel processing system uses a plurality of fuel processing elements, a fuel input and a waste gas input, each of the fuel processing elements having an individual output and the plurality of fuel processing elements having a collective output, and wherein the downstream process has a waste gas output and a dynamic gas load demand. The control system includes a device for receiving communication from the downstream process indicative of the dynamic load demand and a device for controlling the collective output level of the gas in response to the dynamic load demand.

Abstract: A system for generating a desired output gas from an input fuel for use in a downstream process is disclosed. The system includes a plurality of fuel processing units to generate the desired output gas, wherein each of the plurality of fuel processing units includes a reformer which uses waste gas output from the downstream process to facilitate the processing of the fuel. Each of the fuel processing units is operational over a range up to full capacity, wherein the plurality of fuel processing units are interconnected in an collective operating scheme to process the fuel. A control system is provided for controlling the plurality of fuel processing units in response to requirements of a dynamic load demand from the downstream operation. The control system is operative to adjust the operational level of each of the plurality of fuel processing units to produce individual responses from each of the fuel processing units.