A novel second-order sliding mode control of hybrid fuel cell/super capacitors power system considering the degradation of the fuel cell

Abstract

This paper aims to design a novel control strategy of a single converter hybrid power system including a Proton Exchange Membrane Fuel Cell (PEMFC) and super capacitors for electric vehicle applications. The control objective to be addressed in such systems is to smooth the current of PEMFC considering the transient power and sinusoidal disturbance from the load. Moreover, in real-time applications, it is required to ensure the operation by taking into account the component constraints and the degradation of PEMFC. To achieve these goals, a robust nonlinear cascaded voltage control loop is developed in this paper. For the inner voltage loop, a second order twisting controller with dynamic saturation scheme is adopted to ensure the convergence of the DC bus voltage to its reference value as well as to attenuate the oscillations on PEMFC current. For the outer voltage loop, a Proportional Integral controller (PI) with anti-windup scheme is utilized to control the super capacitors voltage at its desired value. Furthermore, in order to consider the degradation of PEMFC in the controlled system, an estimation of the degradation model parameters has been provided by Cubature Kalman Filter. Comparative Hardware-in-the-loop (HIL) tests between the proposed control strategy and the traditional two PI controllers strategy for the hybrid power system is performed. The results of HIL tests verified the effectiveness of the proposed nonlinear control strategy.