Levelling PV Power Variations by Optimal Capacity of ESS in the Operation of a PV-Diesel Hybrid System

In recent times, Global warming is a burning issue as the CO2 density increased highly in the atmosphere. Therefore, clean and renewable energy sources must be introduced to reduce the CO2 density. Among various renewable energy systems, photovoltaic (PV) systems are expected to play a promising role as a clean power electricity source in meeting the future electricity demands. However, the power output of PV systems fluctuates depending on the weather conditions, season, and geographic location. When a significant number of PV systems are connected to the distribution grids of power utilities, PV power output fluctuations cause problems like voltage variations and large frequency deviations in electric power system operation [1]-[3]. Therefore, for the penetration of large PV system¿s output power in the utility without reduction of the reliability of utility power systems, suitable measures must be applied to the PV systems side. On the PV system¿s side, energy storage system (ESS) like batteries can be used as smoothing devices for a PV system¿s output. There have been investigations aimed at improving the performance of PV systems. equipped with batteries [4]-[9]. However, energy storage device increases capital cost and also it needs maintenance. The maintenance cost mainly depends on charge/discharge actions of battery. Therefore, controlling the charge/discharge action along with maintaining the energy storage ratio near 50% is a research subject which needs to be addressed. Besides, optimal capacity and minimum capital cost of the ESS needed to reduce the PV output power fluctuations should be investigated. However, in previous investigations [4]-[9], the optimal size of battery and battery parameters for charge/discharge action are not considered.