Optimal PV-INV Capacity Ratio for Residential Smart Inverters Operating under Different Control Modes

Abstract

The ratio between the photovoltaic (PV) array capacity and that of the inverter (INV), PV-INV ratio, is an important parameter that effects the sizing and profitability of a PV project. It is important to find the balance between cutting down costs by under-sizing the inverter and maximizing profits by generating more energy. This becomes much more important where smart inverters with voltage control abilities are utilized. Smart Inverters have the ability to actively take part in voltage control and, thus, increase the injected power. This would require a larger capacity than usual, as some reactive power flow needs to be accommodated to limit the voltage rise. Excess capacity can be utilized to implement smart inverter functionalities and inject more energy under conditions where conventional inverters would cap their generation. Furthermore, PV-INV ratio studies in the literature focus on large-scale, grid-connected PV systems. This paper focuses on investigating PV-INV ratio for residential PV systems with smart inverters. These are connected to low-voltage distribution systems where voltage rise issue is more apparent. A new simulation tool that can model smart inverter functionalities is utilized to investigate the impact of PV-INV ratio on overall power generation. Different smart inverter functions are implemented for comparison. Based on simulation results, the overall costs and power generation are documented for different PV-INV ratios. Finally, a cost-benefit analysis is performed to find out which PV-INV ratio yields the maximum profits with minimum costs.