Enhancement of Power Sharing in an Islanded AC Microgrid Using Modified Reverse Droop Control Strategy

Abstract

In this paper, an attempt has been made to share the power more accurately among two parallel inverters using a droop-based decentralized control scheme. One of the key problems in exact power-sharing using reverse droop controller (P-V/Q-f) is line impedance mismatch. It initiates several issues regarding frequency and voltage deviation, circulating current, PCC voltage instability, etc. To cater to such problems a modified virtual impedance control loop is added to the existing P-V/Q-f control loop. The reverse droop control scheme is used on a system of two DGs with the same line impedances and different line impedances. Equal power sharing is achieved with a system having the same line impedance, whereas the existing reverse droop controller fails in a mismatched line impedance condition. Hence, the failure of the existing controller is compensated by the inclusion of an additional virtual impedance-based control loop. A block diagram model has been constructed in MATLAB/SIMULINK domain. The simulation results show that the proposed controller can accurately share the active and reactive power keeping the system frequency and PCC voltage within the prescribed limit for a load transient condition