An optimal power sharing and power control strategy of photovoltaic/fuel cell/ultra-capacitor hybrid power system

Abstract

Renewable energy sources experience problems such as deregulation when they are used as stand-alone energy sources. This paper presents an optimal power sharing and power control strategy combining a photovoltaic (PV) array, a fuel cell (FC) stack, an ultra-capacitor (UC) module, and a set of loads. The photovoltaic is the prior energy source while the fuel cell (FC) system is added as a backup source to meet the excess power demand. The ultra-capacitor (UC) is utilized as a buffer storage to compensate the slow dynamic response of the FC during transient and regulate the DC-bus voltage. The power control strategy is designed to work on a two-level arrangement. The top level controls the entire power management, which generates references to low level individual subsystems depending upon solar radiation, temperature, and load conditions. Based on the command signals, each local controller controls the PV, FC, electrolyzer, and UC. The top level also controls the load scheduling during low solar radiation in order to sustain the system operation for 24 h. The performance of the system is tested under real-world record of solar radiation, temperature, and load conditions for Bahria town at Islamabad, Pakistan. The effectiveness of the proposed model in terms of voltage regulation, power transfer, load tracking, and grid stability is verified by Matlab simulation results.