A Novel Supercapacitor/Lithium-Ion Hybrid Energy System with a Fuzzy Logic-Controlled Fast Charging and Intelligent Energy Management System

The electric powered wheelchair (EPW) is an essential assistive tool for people with serious injuries or disability. This manuscript describes the validation of applied research for reducing the charging time of an electric wheelchair using a hybrid electric system (HES) composed of a supercapacitor (SC) bank and a lithium-ion battery with a fuzzy logic controller (FLC)-based fast charging system for Li-ion batteries and a fuzzy logic-based intelligent energy management system (FLIEMS) for controlling the power flow within the HES. The fast charging FLC was designed to drive the voltage difference (Vd) among the different cells of a multi-cell battery and the cell voltage (Vc) of an individual cell. These parameters (voltage difference and cell voltage) were used as input voltages to reduce the charge time and activate a bypass equalization (BPE) scheme. BPE was introduced in this paper so that the battery operates within the safe voltage range. For SC/Li-ion HES, the FLIEMS presented in this paper controls the bi-directional power flow to smooth the power extracted from Li-ion batteries. Moreover, a dual active bridge isolated bidirectional DC converter (DAB-IBDC) was used for power conversion. The DAB-IBDC presented in this paper has the characteristics of galvanic isolation, and high power conversion efficiency compared to the conventional converter circuits due to the reduced reverse power flow and current stresses.