Improved control method for grid-forming virtual synchronous generator based on loop reconstruction mechanism

Grid-forming virtual synchronous generator (GFVSG) can improve the voltage regulation ability and frequency stability of power grid, but it has the problem of grid connected active power dynamic oscillation similar to that of traditional synchronous generator under the conditions of internal disturbance of active power command and external disturbance of power network frequency. To solve this problem, the grid connected active power closed loop equivalent control model of the grid connected system for grid-forming virtual synchronous generator is established, and the reasons for the dynamic oscillation of the grid connected active power of grid-forming virtual synchronous generator under the disturbance of internal active power command and external power network frequency are analyzed in this study. An improved grid-forming virtual synchronous generator control method based on loop reconstruction mechanism (LRM-GFVSG) is proposed, and the corresponding parameter design method is given in detail. Finally, the MATLAB simulation platform as well as experimental platform of 100 kV·A GFVSG grid connected system are established, then the feasibility and superiority of the improved LRM-GFVSG control method in suppressing the dynamic oscillation of the grid connected active power of grid-forming virtual synchronous generator are verified by the simulation and experimental comparison results. Simulation and experimental comparison results show that the grid connected active power closed loop control system of GFVSG is upgraded to a second order oscillation control system due to the introduction of virtual inertia control. Therefore, the grid connected active power and output frequency of the grid connected system of grid-forming virtual synchronous generator are prone to dynamic oscillation and overshoot under the disturbance of internal active power command and external power network frequency. Although increasing the value of the virtual damping parameter of grid-forming virtual synchronous generator can improve the ability to suppress the dynamic oscillation and overshoot of the grid connected active power as well as its output frequency, the steady-state deviation of the grid connected active power is introduced. Compared with grid-forming virtual synchronous generator, the existing grid-forming virtual synchronous generator control method based on feedforward compensation (FFC-GFVSG) as well as the existing grid-forming virtual synchronous generator control method based on feedback compensation (FBC-GFVSG), on the one hand, under the simulation and experimental test conditions where the active power instruction jumps from 20 kW to 60 kW, the improved control method of LRM-GFVSG can improve the transient damping characteristics of the grid tied system, and realize the effective suppression of the dynamic oscillation and overshooting of the grid connected active power as well as its output frequency, and the grid connected active power has a faster dynamic response speed. On the other hand, under the simulation and experimental test conditions where the frequency of the power grid jumps from 50 Hz to 49.95 Hz, the improved control method of LRM-GFVSG can improve the transient damping characteristics of the grid tied system, effectively suppress the dynamic oscillation and overshoot in the grid connected active power as well as its output frequency, and eliminate the steady state deviation of the grid connected active power when the power network frequency deviates from the rated frequency.