Control Approaches for Enhanced sharing of Unbalanced Powers amongst Inverter based DGs in Islanded AC Microgrids

Abstract

Inverter based distributed generators (DGs) in microgrids can be controlled in either of the centralized, distributed or de-centralized approaches. Droop control involves the control of these inverters so as to mimic the behaviour of synchronous generators as in the conventional power system. The strategy is advantageous as it is completely based on local measurements and does not require communication. Under unbalanced loading conditions, only the fundamental powers can be shared in proportion to the DG ratings, when the conventional droop control is employed. The work presented here proposes five modifications for the well known conductance vs. negative sequence power (G vs, Q-) based droop control for enhanced sharing the asymmetrical/imbalance currents among various DGs and can be integrated with the existing conventional or inverse droop controls to improve the power quality within the microgrid. The various control modifications are discussed and simulation results for the same have been presented to validate their performance.