Novel control for redundant parallel UPSs with instantaneous current sharing

A novel distributed control scheme for redundant parallel UPS with instantaneous current sharing is proposed. Current sharing based upon average current method is realized through the share bus interconnecting all the paralleled modules without extra control modules. The share bus consists of only three automatically averaged signals (no matter how many modules in parallel): inverter reference, sensed load current and feedback voltage. Current sharing control is decoupled from reference synchronization control through local feedback of the averaged reference so that inertia of the system reduced greatly. As a result a fast dynamic response and an equal load current sharing capability is ensured, under linear or nonlinear load. System configuration and operation principle are presented while simulation and experiment results are given in detail