A d-q voltage droop control method for inverter paralleling without any communication between individual invertres

This paper presents a current dependent droop control method for equal load sharing of parallel connected inverters without any communication between them. Voltage droop in d and q axis voltage is achieved by using d and q axis currents. Each inverter works on voltage controlled mode where it controls the filter capacitor voltage. The outer voltage control loop generates current reference for filter inductor. The d and q axis voltage references come from d and q axis voltage droops. This d and q axis voltage droops force the inverters to share equal active and reactive power. A local phase locked loop (PLL) is designed to generate phase reference when voltage is available at the point of common coupling (PCC). If voltage is not available, inverter starts with its own internal phase reference. When all inverters come into operation, they share equal active and reactive power due to the proposed droop control. The strategy has been verified with simulation and experiments and the results are presented in this paper.