Research on Power Quality of Critical Loads of Electric Springs Based on Quasi-PR Dual Closed-loop Control Strategy

Aiming at the problems of the strategy for dual PI closed-loop control in the grid voltage fluctuation, voltage at the critical load in the Electric Spring (ES) system has the steady state error as well as the high harmonic content, this paper introduced the quasi-PR controller into the second generation of the Electric Spring (ES-2), and researched a strategy for dual closed-loop control utilizing the quasi-PR controller for both the external voltage loop and the internal current loop. The working process of this control strategy is introduced, the control loop is designed, and the stability of the electric spring system based on the quasi-PR controller is analyzed. Through simulation comparison with the control strategy for dual PI controllers on the MATLAB/Simulink platform, it is verified that the strategy for dual closed-loop control with quasi-PR controllers can better stabilize voltage at the critical load and suppress the harmonics on voltage at the critical load during the fluctuation of the grid voltage.