An improved droop control strategy based on changeable reference in low-Voltage microgrids

Abstract

This paper proposes an improved droop control strategy based on changeable reference in low-voltage microgrids. To restore running frequency of distributed generation to a rated value without affecting its reactive power output, changeable frequency reference, mainly compensating for frequency deviation, are proposed corresponding to various load demands. In terms of active power sharing inaccuracy associated with mismatched line impedance, changeable voltage amplitude reference is proposed to obtain a droop line suitable for the actual voltage of distributed generations. By further improvement of the active droop coefficient, power sharing is accurate with a difference in actual voltages of distributed generations. Virtual negative inductance is used to neutralize the redundant line inductance for strictly improving sharing accuracy. A robust control method based on Lyapunov function is used to handle the robustness problem in case of load variation. The control scheme is entirely decentralized, so communication links among distributed generations are redundant. Finally, simulation studies demonstrate the effectiveness of a control strategy.