A first AC power source comprising a power plant (18), and a second power source, typically grid (10), are normally connected via a high speed isolation switching means (19) to provide sufficient AC power to a critical load (14). The power plant (18) comprises a power generating means, e.g. a fuel cell,...http://www.google.de/patents/US7061139?utm_source=gb-gplus-sharePatent US7061139 - System for providing assured power to a critical load
