Method and system for controlling output of fuel cell power generator

A method for controlling the output of a fuel cell power generator having a fuel cell which generates a direct-current output when supplied with fuel gas from a fuel reformer, said direct-current output being converted by inverting means into an alternating-current output to be fed to a power system, by using an output controlling system having:

• an output control regulator for controlling the output current of said inverting means as close to the current value corresponding to the output power set value of said inverting means as possible;
• a current command value computing unit for updating a current command value on the basis of the output signal of said output control regulator;
• and
• an inverting means controller for controlling the output current of said inverting means as close to said current set value as possible;
• the method comprising the steps of:
• setting an output power set value of said fuel cell;
• detecting the fuel gas flow rate flowing into said fuel cell or the fuel exhaust gas flow rate flowing out of said fuel cell;
• computing a current value corresponding to the maximum available output power value of said fuel cell on the basis of the detected flow rate;
• selecting and outputting either the computed current value corresponding to the maximum available output power value or a current value corresponding to said output power set value, whichever is the lower;
• and
• outputting to said output control regulator a signal for correcting the current value corresponding to said output power set value so that the detected output current value of said fuel cell is controlled as close to the output current value of said low level selector as possible.

A method for controlling the output of a fuel cell power generator having a fuel cell which generates a direct-current output when supplied with fuel gas from a fuel reformer, said direct-current output being converted by inverting means into an alternating-current output to be fed to a power system, by using an output controlling system having:

• an output control regulator for controlling the output current of said inverting means as close to the current value corresponding to the output power set value of said inverting means as possible;
• a current command value computing unit for updating a current command value on the basis of the output signal of said output control regulator;
• and
• an inverting means controller for controlling the output current of said inverting means as close to said current set value as possible;
• the method comprising the steps of:
• setting an output power set value of said fuel cell;
• detecting both the fuel gas flow rate flowing into said fuel cell and the fuel exhaust gas flow rate flowing out of said fuel cell;
• computing the fuel utilization factor on the basis of said flow rate of the fuel gas flowing into said fuel cell and the flow rate of the fuel exhaust gas flowing out of said fuel cell;
• computing a current value corresponding to the maximum available output power value of said fuel cell on the basis of the computed fuel utilization factor;
• selecting and outputting either the computed current value corresponding to the maximum available output power value or a current value corresponding to said output power set value, whichever is the lower;
• and
• outputting to said output control regulator a signal for correcting the current value corresponding to said output power set value so that the detected output current value of said fuel cell is controlled as close to the output current value of said low level selector as possible.