Auto-master-slave control technique of parallel inverters in distributed AC power systems and UPS

This work presents a new control scheme: auto-master-slave control technique of parallel connected SPWM inverters. The control scheme ensures a fast dynamic response and precise load current sharing capability. Based on auto-master-slave control technique, the control circuitry employs the real power share bus and reactive power share bus interconnecting all the paralleled inverters. With the power share buses and the power deviation controllers, the paralleled inverter with highest output power becomes the master inverter; other inverters become slave inverters. Master inverter drive the power bus, and the power deviations in slave inverter module are calculated by the power sharing controller. Hereafter, the inverters compensate for the frequency and amplitude of output voltage, and then the unbalance power was eliminated. An experiment system was built to verify this control scheme, and the results indicate the precise power balance performance for parallel operation.