Optimal Sizing of Photovoltaic and Battery Energy Storage Systems Incorporating Constant Current and Constant Power Load Models

Load modelling is critical in power system analysis, significantly affecting voltage stability, power flow, and the sizing and placement of Distributed Generators (DGs). Current research has primarily focused on optimal sizing methodologies for DGs and battery energy storage systems, predominantly utilizing constant load models. This approach fails to capture the dynamic and non-linear characteristics of actual load behaviour, which affects the voltage stability. The practical loads are composed of ZIP loads (Constant Impedance Load -CIL-‘Z’, Constant Current Load- CCL-‘I’ and Constant Power Load-CPL-‘P’). In this context, this research evaluates the effect of CCL and CPL modelling on the optimal sizing of system components, particularly in light of the growing prevalence of battery-operated loads. The study proposes an optimal system size designed to accommodate the diverse load demands represented by ZIP loads affecting system voltage across various applications, including residential, industrial, commercial, and agricultural settings. The analysis is conducted using the Improved Particle Swarm Optimization technique with consideration of a ±5% variation in the system's rated voltage. The present study evaluated the minimum total annual cost over a twenty-year timeframe, utilizing actual site data. The results indicate a maximum number of system components in the agricultural load due to the dominating CPL. The results also propose the inclusion of 10% CCL in residential, industrial, and commercial loads due to the increasing reliance on battery-operated systems: electric vehicles and hybrid electric vehicles.