| Abstract |
A parallel type Uninterruptible Power Supply (UPS) operates parallel to the mains via an inductor. lt has three fundamental modes of operation: mains operation ( when mains voltage is OK ), emergency operation ( mains failure ), and bypass ( UPS failure ). UPS systems can be connected in parallel on their input and output terminals, for redundancy or system expansion. Problems arise on circulating reactive power, equal load sharing, circulating DC current and the coordination of the states in which each UPS system may be. These problems can be solved by adequate control and a minimum of information that is exchanged between the participating UPS systems. |
