Enhanced digital PI control with state-variable feedback loop for DC electric springs

Abstract

DC electric springs (DCES) have recently been proposed as a potential solution for resolving the issue of power supply-demand imbalance of DC microgrids caused by the fluctuations of intermittent renewable energy sources (RES). Existing control of DCES based on conventional PI compensation are designed for good steady-state performance. The dynamic performance of DCES has not been explored. In this paper, an enhanced digital PI control comprising a state-variable feedback loop, aimed at optimizing both the steady-state and transient performances of the DCES, is proposed. Experiment results show that with this control, faster transient of the DCES is achievable and that the DCES can rapidly tame the possible fluctuations of renewable energy sources in a 48 V DC test grid more effectively.