Design and implementation of Battery/SMES hybrid energy storage systems used in electric vehicles: A nonlinear robust fractional-order control approach

Abstract

This study attempts to develop a novel nonlinear robust fractional-order control (NRFOC) of a battery/superconducting magnetic energy storage (SMES) hybrid energy storage system (BSM-HESS) used in electric vehicles (EVs), of which rule-based strategy (RBS) is adopted to optimally assign the power demand. Based on the online perturbation estimation via a high-gain perturbation observer (HGPO), NRFOC is devised as the underlying controller which is able to fully compensate nonlinearities and modelling uncertainties of BSM-HESS through a fractional-order PID controller as the additional input. Here, the introduced fractional differentiator and fractional integrator can considerably improve the control performance while only two states, e.g., the battery current and DC bus voltage, need to be measured, in which no accurate system model is required. Case studies are undertaken to evaluate the effectiveness and merits of NRFOC to other control schemes. Moreover, the control costs of NRFOC required in heavy load condition is just 79.00%, 87.11%, and 82.96% to that of PID control, feedback linearization control (FLC), and sliding-mode control (SMC), respectively. At last, its implementation feasibility is validated by hardware-in-the-loop (HIL) experiment based on dSpace platform.