An advanced synchronization and current-sharing method for paralleled DC/AC inverters without interconnection

In this paper, an advanced synchronization and current-sharing method for paralleled DC/AC inverters without interconnection is presented. In the synchronization method, the output voltage and current of individual inverter are detected to calculate the equivalent reactive power. As the equivalent reactive power can reflect the phase information, so the inverter can adjust its own phase to track the voltage of the output bus by controlling its value of equivalent reactive power. The current-sharing method uses the AC signal on the output line to realize current-sharing control. The frequency of the small signal is inversely proportional to the output active power of the inverter. By comparing RMS of the local small signal with that of the overall signals added to the bus, the controller then regulate its own reference voltage to track the minimum output active power of the inverter in the system. An experiment system was built to verify the proposed method, and the results indicate the precise power balance performance for parallel operation