Control strategies of grid-connection and operation based on active disturbance rejection control for virtual synchronous generator

Virtual synchronous generator (VSG) control technology is an attractive solution for large-scale renewable energy grid-connected. Aiming at the problem of large impulse current instantly when the VSG is connected to the grid and the deviation of output power in the operation of grid-connection, control strategies of grid-connection and operation based on active disturbance rejection control (ADRC) is proposed. Firstly, a linear/nonlinear active disturbance rejection switching control phase lock loop (L/NADRSC-PLL) and its pre-synchronization strategy are designed for VSG grid-connection. When the tracking error is large, the proposed L/NADRSC-PLL choose LADRC to improve the tracking speed of the system, while NADRC is selected in the case of small tracking error and fluctuating PCC voltage amplitude, frequency and phase to improve the steady-state accuracy and antidisturbance capability of the system. Then, a power decoupling control method based on LADRC is developed to eliminate output power deviation. Through using the estimates of coupling terms and disturbances obtained from an extended state observer, the aforementioned issue caused by power coupling can be alleviated. Besides, the controller stability is analyzed by the small signal model of the proposed control strategies. Finally, the correctness and effectiveness are verified based on both the simulation and hardware-in-loop experiments.