Secondary power source for use in a back-up power system

A regulated DC power supply comprising:

• a plurality of rectifiers coupled between a primary AC power source and a DC bus, the rectifiers adapted to convert AC power from the AC power source to DC power for a load;
• a regenerative fuel cell (RFC) arrangement electrically coupled to a plurality of power converters that are coupled in parallel with the DC bus, the converters adapted to condition a DC power output of the RFC arrangement to the load;
• and
• a fuel cell controller communicatively coupled with the fuel cell arrangement and adapted to initiate DC power output from the fuel cell arrangement upon detecting an AC power outage.

A method of providing extended backup power to a load via a power plant having a battery arrangement, the method comprising:

• providing DC power to the load from the battery arrangement via a DC bus upon interruption of a primary power source;
• shedding a portion of the load when the DC bus voltage reaches a predetermined transition voltage;
• providing power to the DC bus at or below a predetermined DC bus voltage from a secondary power source;
• using a secondary power source controller to share current between the battery arrangement and the secondary power source;
• and
• upon detecting primary power source resumption, switching the load from the secondary power source and battery arrangement to the primary power source via the secondary power source controller.