Abstract
Rapidly depleting oil and natural gas resources, global warming issue, and depletion of fossil fuels are motivating the development of alternative technology for vehicular systems. Thus, an increasing number of studies have been conducted on fuel cell electric vehicles (FCEVs). This paper proposes a modeling and nonlinear control for hybrid energy storage system (HESS) in FCEVs. HESS consists of fuel cell (FC) as the main source and battery and ultracapacitor (UC) as secondary sources. Each source is connected to DC bus via DC-DC converter: FC is connected to DC bus via boost converter, while battery and UC are connected to DC bus via buck-boost converter. Based on the nonlinear behavior of power sources and converters, a dynamic model of the system is developed. A nonlinear control technique based on Lyapunov theory is applied to meet the following requirements: (1) accurate DC bus voltage regulation and (2) rapid tracking of battery and UC current to their desired reference values. Both mathematical analysis and simulations are performed to prove the asymptotic convergence of the proposed controller. To verify the performance of the controller, simulations have been done on MATLAB/Simulink, which show that the proposed controller ensures the stability of closed loop system and meet all the control objectives.