A LADRC and Self-Adaptive Combination Control Method of VSG for Transient Stability Enhancement During Voltage Sag Compensation

The quantity of distributed resources and the proportion of sensitive inrush loads in the new distribution networks are growing, resulting in a series of problems, such as voltage sags and voltage fluctuations. To suppress the voltage sags caused by faults in the grid, the grid-forming inverters for connecting distribution grids and energy storage may need to be switched between off-grid and on-grid modes. However, significant differences in phase angle during mode switching can lead to longer grid-connection time and frequency fluctuations outside the safe range. To improve the inverter's transient stability while switching between these modes, a linear active disturbance rejection control (LADRC) and self-adaptive combination control method for virtual synchronous generator (VSG) is proposed. The design method of pre-synchronization by LADRC is investigated, then, the combination of the coordinated self-adaptive control strategy with the pre-synchronization is given. Finally, the simulation outcomes verify the correctness and efficiency of the proposed control method.