Fuel cell power generation system and method of controlling the same

A fuel cell power generation system, comprising:

• a fuel cell subsystem including a plurality of fuel cell stacks connected in parallel with each other, each of said fuel cell stacks comprising at least one fuel cell and a dc breaker connected in series therewith;
• a source of raw fuel gas;
• a raw fuel gas feed conduit for feeding said raw fuel gas;
• a reformer for forming fuel gas, said reformer having first, second and third inputs, and an output, the first input being connected to said source of raw fuel gas through said raw fuel gas feed conduit;
• a fuel gas feed conduit interposed between the output of said reformer and said fuel cell stacks for feeding fuel gas to said fuel cell stacks, the fuel gas feed conduit having a fuel gas shut-off valve for each of said fuel cell stacks;
• a fuel gas exhaust conduit connected to said fuel cell stacks and to the second input of said reformer, said fuel gas exhaust conduit having a fuel gas exhaust shut-off valve for each of said fuel cell stacks;
• a source of oxidant gas;
• an oxidant gas feed conduit for connecting said source of oxidant gas to said fuel cell stacks;
• an oxidant gas exhaust conduit connected to said fuel cell stacks and to the third input of said reformer, said oxidant gas exhaust conduit having an oxidant gas exhaust shut-off valve for each of said fuel cells stacks;
• said reformer receiving exhaust oxidant gas and exhaust fuel gases from said oxidant and fuel gas exhaust conduits, respectively, for reforming said exhaust fuel gas into said fuel gas and feeding said fuel gas to said fuel cell subsystem;
• a first bypass conduit interposed between said reformer and said fuel gas exhaust conduit, said first bypass conduit having a first flow rate control valve therein;
• a second bypass conduit interposed between said oxidant gas feed conduit and said oxidant gas exhaust conduit, said second bypass conduit having a second flow rate control valve therein;
• a plurality of abnormality detectors, one of said detectors being connected to each of said fuel cell stacks for detecting the output thereof, each of said abnormality detectors generating a shut-off signal when the output of the fuel cell stack to which it is connected decreases to an amount below which the total load on said source of oxidant gas and on said reformer has reached a predetermined minimum value required for operation of said power generation system, said shut-off signal shutting the fuel gas, fuel gas exhaust, oxidant gas and oxidant gas exhaust shut-off valves, operating said first flow rate control valve to bypass a part of the fuel gas from said reformer to said fuel gas exhaust conduit, operating said second flow rate control valve to bypass a part of the oxidant gas from said source of oxidant gas to said oxidant gas exhaust conduit, and opening the dc breaker of the fuel cell stack connected to the abnormality detector which generated said shut-off signal;
• and
• an inverter electrically connected in parallel with said at least one fuel cell of each of said fuel cell stacks, through said dc breaker, for converting a DC output of said fuel cells to an AC output.