Double Closed-Loop Control Strategy for Electric Springs Based on PI Controller

Electric Springs (ESs) can effectively solve the problem of load side voltage instability caused by the voltage fluctuation on the grid side. Although the single closed-loop control strategy based on the root mean square (RMS) value of the voltage at the point of common coupling (PCC) can maintain the PCC voltage stability, the harmonics on the load side and the ES output voltage will be distorted largely. In this paper, a double closed-loop control strategy with an outer voltage loop and an inner current loop is proposed to address the problem mentioned above. The simulation results show that the improved double closed-loop control strategy can effectively suppress the harmonics on the PCC voltage as well as the ES output voltage.