Research on the Control Strategy of Microgrid Inverter Based on Adaptive Virtual Synchronous Generator System

Abstract

Considering the high penetration impact on the grid system brought by the grid-connected distributed energy, there is the fact that the conventional grid-connected inverters do not have the advantage of rotational inertia, which can increase the operational risk of the system. Combined with the wind farm multi-terminal DC transmission system, an adaptive virtual synchronous generator control strategy based on the adaptive virtual governor function is proposed. Combined with the virtual synchronous governor module, a virtual synchronous generator (VSG) control strategy with inertial response and primary frequency regulation capability is established. However, considering the fluctuating and intermittent characteristics of distributed power supply, the power supply and demand imbalance will lead to the load state of the energy storage equipment exceeding the safe operation range during the long-term operation. Based on aforementioned questions, the method of adjusting the sag coefficient according to the charge state is extended to the VSG-based control. By introducing the concept of adaptive sag characteristics, the VSG control is further improved by using the method of shifting sag characteristics. The improved VSG control method reduces the impact on the system stability and represents more conducive to the rational distribution of active power and the rapid adjustment of the charge state. The simulation results validate the rationality of the proposed control strategy by using the Matlab/Simulink tool.