Optimal PV–FC hybrid system operation considering reliability

Abstract

This paper presents an approach for optimal operation of a grid-connected hybrid system to maximize the system expected generated energy while maximizing the electricity sale revenue. The hybrid system consists of a photovoltaic (PV) module, an electrolyser (EL), hydrogen storage tank (HS) and a proton exchange membrane (PEM) fuel cell (FC). The generated energy is sold to the distribution grid. During the grid interruptions, the hybrid system output is used as an emergency supply to serve the local load, hence increasing the supply reliability. The proposed approach splits the whole problem in two sub problems: revenue maximizing problem (RMP) and expected generation maximizing problem (EGM). RMP finds optimal hourly electricity selling considering hourly variations in electricity price and solar irradiance subjected to HS minimum pressure. EGM uses RMP results and HS minimum pressure to determine expected generated energy (EGE) based on the proposed 4-state generation reliability model for the system. A bi-section search is finally used to find the optimum level for HS minimum pressure to maximize EGE while keeping selling revenue at highest possible level. The impact of optimal system operation on EGE is then evaluated. A series of analyses have been conducted to assess the capability and applicability of the proposed method. Suitable economic indices have also been proposed to evaluate reliability cost/worth of hybrid system application to improve load reliability.