Applications of battery/supercapacitor hybrid energy storage systems for electric vehicles using perturbation observer based robust control

This paper designs a robust fractional-order sliding-mode control (RFOSMC) of a fully active battery/supercapacitor hybrid energy storage system (BS-HESS) used in electric vehicles (EVs), in which two bidirectional DC/DC converters are employed to decouple battery pack and supercapacitor pack from DC bus based on the classical 5th-order averaged model. Rule-based strategy (RBS) is firstly employed as the energy management strategy (EMS) to generate the battery current reference. Then, RFOSMC scheme is developed as the underlying controller to globally compensate nonlinearities and various uncertainties of BS-HESS by the real-time perturbation estimation via a sliding-mode state and perturbation observer (SMSPO). Two outputs are chosen, e.g., battery current and DC bus voltage, which are also the only states that need to be measured for the control system design, thus RFOSMC is relatively easy to be implemented. The control performance of RFOSMC is thoroughly investigated in comprehensive case studies to that of other three typical controllers. Finally, a hardware-in-the-loop (HIL) test is undertaken to validate the effectiveness of the proposed control scheme.