Robust fractional-order PID control of supercapacitor energy storage systems for distribution network applications: A perturbation compensation based approach

Abstract

This study proposes a robust fractional-order PID (RFOPID) control approach for supercapacitor energy storage (SCES) system applied on distribution network. At first, nonlinearities, unmodelled dynamics, parameter uncertainties, and external disturbances of SCES systems are effectively estimated by the high-gain perturbation observer (HGPO). Afterward, a fractional-order PID (FOPID) controller is employed for online complete compensation for the perturbation estimation to enhance the robustness. Moreover, the performance of dynamical responses are significantly improved due to the fractional differentiator and integrator orders. In addition, accurate SCES system model is not needed while merely dq-axis currents require to be determined. Meanwhile, controller gains and observer gains can achieve optimal adjustment by interactive teaching-learning optimizer (ITLO). Four case studies assess the practical performance of RFOPID control compared with that of other typical linear/nonlinear control strategies. At last, a dSpace based hardware-in-the-loop (HIL) test is performed to verify its effectiveness for practical applications.