Abstract: Because of the resistance and mismatch of line impedance in low-voltage microgrid, the multi-inverters controlled by conventional virtual synchronous generator (VSG) often have problems with power coupling and uneven reactive power distribution. To address these issues, a reactive power distribution control strategy for multi-VSG based on coupling point voltage estimation is proposed. First, virtual impedance technology is introduced to design equivalent output impedance as inductance to realize power decoupling. Secondly, the voltage of the common coupling point is accurately estimated. In order to decouple the line impedance from the reactive power, negative feedback and an integral link based on the common coupling point estimation voltage is introduced into the excitation controller. Finally, a dynamic virtual impedance mechanism is implemented. The reactive power is used to adjust the voltage drop of the common coupling point, and the influence of the impedance mismatch on the circulating current is reduced, thereby the power quality is improved. The simulation results verify the effectiveness of the proposed control strategy.

Key words: virtual synchronous generator, parallel inverter, dynamic virtual impedance, powerp sharing, circulation current suppression