Intelligent Power Allocation with Load Disturbance Compensator in Fuel Cell/Supercapacitor System for Vehicle Applications

A fuel cell-based hybrid power system with a supercapacitor can downsize the fuel cell power rating and shows good dynamic characteristics. However, power distribution between fuel cell and supercapacitor is challenging, and inappropriate power allocation strategy will easily cause over-charge or overdischarge of supercapacitor. Also, the DC bus voltage fluctuation is always encountered during the acceleration and deceleration of the vehicle. This paper proposes an intelligent power allocation method based on a low-pass filter. The adaptive cut-off frequency is applied to avoid over-charging and over-discharging the supercapacitor, and the cut-off frequency is calculated by cutting the load spectrum with allocation ratio changing with the state of charge (SoC) of the supercapacitor. A load disturbance compensator is also proposed to suppress the DC bus voltage fluctuation when the load variation occurs. According to the hybrid system model developed with commercially available devices, the feasibility of the strategy is verified by MATLAB/Simulink. The simulation results show that the SoC of the supercapacitor is effectively controlled and the DC bus voltage fluctuation is significantly reduced.