Optimal sizing of hybrid renewable energy system via artificial immune system under frequency stability constraints

Abstract

An efficient sizing procedure for renewable energy resources (RESs) is a mandatory requirement for the implementation phase. The sizing procedure is mainly demand curve dependent, and the proper sizing certainly optimizes system components and hence reduces the cost. This article proposes an innovative optimal sizing procedure for wind/solar/battery hybrid renewable power systems (HRPSs) using the Artificial Immune System (AIS) technique. The optimal sizes of photovoltaic arrays, wind turbines, and batteries which fulfil the demand requirement with the least percent of load interruptions are identified. HRPSs usually suffer from the uncertainty of RESs and the absence of synchronous inertia. Energy storage systems (ESSs) could successively remedy these deficiencies. This article advises the application of ESS for providing the primary frequency control during any contingency/fall of frequency out of its normal limits. Accordingly, ESS acts as virtual synchronous inertia that balances between demand and generation during disturbance. The proposed sizing procedure is analysed as a constrained optimization problem. The constraints ensure high reliability power supply along with the frequency stability constraints. Therefore, the proposed sizing procedure has the advantages of minimized HRPS cost, improved system security, and regulated frequency. The uncertainty of RESs is considered in the proposed sizing procedure, to improve the applicability of the obtained results. The proposed procedure algorithm is correlated via comparison with Practical Swarm Optimization, a fertile optimization method. A case study for evaluating the proposed sizing approach is Qena AL-Gadida city, Qena province, Egypt. The power supply of this city is considered as a Microgrid. MATLAB is used for coding AIS and systems under concern. Numerous operating scenarios are considered to test the functionality of the proposed sizing and primary function regulation ability of its ESS. The results reveal the reliability and applicability of the advised sizing procedure. Moreover, adopting primary frequency regulation of ESS resulted only in a slight increase in the overall costs.