Optimization method and stability analysis of MMC grid-connect control system based on virtual synchronous generator technology

Abstract Aiming at the issue of how to design controller parameters and analyze system stability when modular multilevel converter (MMC) adopts virtual synchronous generator (VSG) control technology. Firstly, this paper derives the parameter correspondence between the grid-connected MMC system and the synchronous generator (SG) system, and obtains the relationship between the virtual inertia parameter and damping parameter with specific structural parameters of MMC, then the optimization method of key parameters in the main controller of MMC grid-connected system is determined. That is to add the optimized inertia parameters and damping parameters to the active-frequency controller, the flux linkage feedback loop and the reactive differential compensation link to the reactive-voltage controller, the stability of MMC grid-connected system was analyzed by adjusting key parameters, and the optimal inertia parameters and damping parameters of the MMC grid-connected system during stable operation was analyzed. Finally, using MATLAB/Simulink to build a simulation model of MMC grid-connected system based on VSG control, the feasibility and correctness of the proposed optimization method for key parameters were verified, and the stability of the system was analyzed. The results showed that the key parameters of the main controller combined with the MMC unique structure were more suitable for the MMC grid-connected control system, which improved the stability of the system.