Optimization of an isolated photo-voltaic generating unit with battery energy storage system using electric system cascade analysis

This paper presents an improvement to the iterative method of electric system cascade analysis (ESCA) for the optimisation of an isolated PV system with battery energy storage system (BESS) for a residential load. The ESCA algorithm is implemented on MATLAB software environment with Final Excess Energy (FEE), Loss of Power Supply Probability (LPSP) and system cost as optimization constraints. The load, temperature and solar radiation profiles are considered for a year, based on historical data. Practical losses in solar radiation reaching the PV collector surface are considered for analysis. Change in PV efficiency due to variation in temperature and change in charge/discharge efficiency of the battery based on current state of charge (SOC) of BESS are taken into consideration which further bolsters the credibility of the ESCA methodology. The ESCA methodology is used to optimize a PV-BESS system for a residential load with average daily consumption of 26.1 kWh. The optimized result obtained from improved ESCA are compared and verified with benchmark HOMER software.