Research on Circulating Current Control Strategy for Parallel VSG Based on Adaptive Virtual Impedance

Abstract

 To address the circulating current and uneven power distribution issues 
in multi-virtual synchronous generator (VSG) parallel systems caused by incon
sistent line impedances, an improved control strategy introducing dynamic vir
tual impedance is proposed. By analyzing the active power-frequency and reac
tive power-voltage control characteristics of VSG, the influence mechanism of 
line impedance differences on power distribution accuracy and circulating cur
rent is revealed. In the proposed strategy, adaptive virtual impedance is intro
duced to enhance the inductive feature of the output impedance, achieving power 
decoupling, and a voltage feedback integral link is combined to compensate for 
the voltage drop caused by virtual impedance. Simulation results show that this 
strategy can effectively suppress the circulating current between parallel VSGs, 
achieve precise sharing of active and reactive power, and improve system stabil
ity and power quality.