Reactive Power Equalization Control Strategy of VSG Improved by Low Voltage Microgrid

Due to the difference in line impedance of low-voltage microgrid, the power coupling existing in parallel operation of virtual synchronous generator(VSG) will lead to uneven power distribution and circulation current. Firstly, the cause of power coupling in parallel equivalent circuit are analyzed, and it is shown that both power angle and impedance angle will have an important impact on power coupling. For this reason, a reactive power sharing control strategy is proposed to improve VSG, and power angle compensation is added to the virtual impedance change to correct the value of virtual impedance. This control strategy can realize power sharing better and reduce circulation current. For the problem of voltage drop caused by virtual impedance, the voltage compensation term is added in the reactive power loop to increase the voltage amplitude and improve the power quality of the inverter output voltage. Finally, the overall closed-loop system output impedance transfer function is established to ensure the stability and dynamic performance of the system. Two VSGs are built in Matlab/Simulink to verify the feasibility of the proposed control strategy.