Design of voltage stabilization and power sharing control method via virtual complex impedance

Abstract

Microgrid (MG) usually operates in medium/low voltage systems, where the line impedance parameters are mainly resistive, and traditional P-f/Q-U droop control is no longer applicable. According to the line parameters characteristics of the off-grid MG with medium/low voltage, the P-U/Q-f droop control is adopted in this study, where the virtual complex impedance composed of a virtual negative inductance and a virtual resistance is introduced in the control loop. The virtual negative inductance is used to reduce the power coupling caused by the inductive component of the system impedance. The virtual resistance is implemented to enhance the resistive component and adjust the impedance matching degree for raising the accuracy of power sharing. However, the power sharing is still affected by the system hardware parameters, meanwhile, the voltage deviation caused by the droop control and the virtual impedance exists. In this study, a novel voltage stabilization and power sharing control method based on the virtual complex impedance is investigated to achieve accurate power sharing without the impact of hardware parameters variations and to improve the voltage quality. Numerical simulations are provided to verify the effectiveness of the proposed control method in comparison with traditional frameworks.