Dual-mode virtual synchronous generator adaptive frequency characteristic control

Aiming at the frequency fluctuation problem caused by load casting and switching in AC microgrids, which in turn leads to system stability problems, this paper carries out an improvement of the control scheme on the basis of existing VSG control. When the island operation of a microgrid occurs to cast large-capacity active loads, the primary frequency regulation function of simulated droop control cannot meet the frequency requirements in some scenarios and generates frequency steady-state errors. The frequency deviation is used for adaptive secondary frequency regulation to improve the active power control loop and quickly restore the system frequency in the island mode. To enhance the stability and frequency characteristics of a microgrid system in the grid-connected mode, a control strategy based on the improved parameter synergistic adaptive adjustment of the VSG frequency change is proposed. The influences of relevant parameters on the dynamic performance of the system are analyzed, and the stability of the improved strategy is verified from the perspective of transient energy. Control models under island and grid-connected conditions are constructed in simulation software to simulate and verify the viability and accuracy of the proposed control strategies.