Nonlinear control and energy management of the hybrid fuel cell and battery power system

This paper deals with the problem of controlling a hybrid energy storage system (ESS), used in hybrid electric vehicles. The system consists of a PEM fuel cell and batteries as sources and two DC-DC power converters. A nonlinear controller and an energy management system (EMS) are developed. Firstly, an appropriate nonlinear model of the studied system is elaborated. Then, a nonlinear controller is elaborated using Lyapunov theory to ensure the following objectives: i) tight DC-bus voltage regulation, ii) perfect tracking of the battery current to its reference; and iii) asymptotic stability of the closed-loop system. Secondly, using Bellman's principle of optimality, the EMS is designed to generate an optimal reference signal of the battery current. The objective is to share the load power between the fuel cell and the battery minimising the hydrogen consumption. It is shown, finally, using theoretical analysis and simulations that the objectives of the nonlinear controller and the EMS are achieved whatever the used vehicle and the traction motor. Interestingly, the only used information on the traction part is the load current.