Variable structure-based control of fuel cell-supercapacitor-battery based hybrid electric vehicle

Hybrid electric vehicles (HEVs) are getting attention due to their importance in the transport Industry. Clean energy generation and effective utilization is rapidly growing research area. Fuel cell based electric vehicles have many advantages over conventional vehicles. The fuel cell is a massive source of clean energy that overcomes the issues of conventional vehicles such as; global warming and high fuel cost. The hybrid energy storage system (HESS) of the proposed vehicle consists of three power sources; fuel cell (FC), battery, and a supercapacitor (SC) which are connected to the DC bus through the DC-DC power converters. DC bus is further connected to DC-AC inverter which is used to run the electric motor of vehicle. In this paper, three nonlinear controllers namely; Sliding Mode Controller (SMC), Integral sliding mode controller (ISMC) and Double integral sliding mode controller (DISMC) have been proposed to achieve the desired control objectives. The purpose of ISMC and DISMC is to eliminate the steady-state error and mitigate the chattering effect inherent in SMC. The main objectives of proposed controllers are; tracking of battery and supercapacitor currents to their reference values, voltage regulation of DC bus and the global stability of the system. The proposed controllers have then been simulated using MATLAB/Simulink to analyze their comparative performance. It is noted that DISMC could alleviate the steady-state error significantly.