Research on Reactive Power Equalization of Microgrid Based on Adaptive Virtual Impedance

During the operation of an isolated microgrid, the mismatch of feeder impedance will lead to the uneven distribution of reactive power output from the shunt inverter, while the traditional droop control only considers the fundamental positive sequence voltage, which is difficult to achieve equal distribution of reactive harmonic power. Therefore, this paper combines reactive harmonic power and fundamental negative sequence reactive power to construct an adaptive virtual impedance for harmonic voltage compensation. The signal extraction and separation module are used to obtain the positive and negative sequence fundamental voltage and current as well as the current harmonic components of the specific order. The adaptive virtual impedance is constructed based on the fundamental negative sequence reactive power and reactive harmonic power, and the voltage compensation amount is calculated. Then, the voltage compensation amount and the fundamental positive sequence voltage value are used as the voltage and current double-loop control input to equalize the reactive power and reduce the loop current between inverters. A microgrid simulation model is built in MATLAB/Simulink to verify the effectiveness of the proposed adaptive virtual impedance voltage compensation scheme under two operating conditions.