Improving During and Postfault Response of Fuel Cells in Symmetrical and Asymmetrical Grid Fault Cases

Abstract

High-gain PID controllers with fast response are the most common schemes that are used to control polymer electrolyte membrane fuel cells (PEMFCs). However, during grid voltage sags, due to their fast response, these controllers may get saturated. Consequently, the PID controller loses the ability to control PEMFC during grid's voltage restoration period, which is not desirable for the grid. In this paper, a control strategy using proxy-based sliding mode control (PBSMC) is proposed to enhance the postdisturbance recovery of PEMFCs. The proposed control scheme operates similar to high-gain, fast response PID controllers during normal operation and small disturbances. However, during large disturbances that cause the conventional controller to reach its limit, PBSMC shows a slow and overdamped response. This leads to fast and smooth resume to the predisturbance trajectory. Additionally, in this paper, a systematic approach is developed to reduce the voltage oscillations of the capacitor of a dc/dc converter during asymmetrical faults. By employing this method, the performance of PEMFC power plant under asymmetrical faults is enhanced. Simulation results show that the proposed controller and voltage oscillation compensation method improve the response of PEMFCs to different types of faults.