Multi-inverter UPS system with redundant load sharing control

The concept of a redundant multi-inverter UPS (uninterruptible power supply) system which includes extended monitoring of the status and the operating conditions of all power electronic equipment is described. Each block of the UPS system is monitored by two independent microcomputers that process the same data. The microcomputers are part of a redundant distributed monitoring system that is separately interlinked by two serial data buses through which they communicate. They establish a hierarchy among the participating blocks by defining one of the healthy inverter blocks as the master. The actual master runs the central synchronizing unit for the entire system, whereas the slave units perform the control of equal active and reactive load sharing. Operation and fault detection are experimentally illustrated in a dual inverter system with a rating of 10 kVA of redundant power