Inverter size optimization for grid-connected concentrator photovoltaic (CPV) plants

Abstract

Concentrator PV systems utilize different part of solar irradiation arriving at the Earth's surface and typically generate different power profiles than traditional flat plate PV or thin film. These factors need to be taken into account during plant design, particularly for inverter sizing strategies, and will result in very different inverter size/ rated DC power ratios than flat plate PV systems. This paper describes a methodology for sizing inverters for CPV power plants that optimizes the financial return of a project, taking into account energy generation profiles and financial parameters for large scale projects. Using hourly CPV power output throughout the year for a number of locations with high Direct Normal Irradiance (DNI) in southwest US, the optimal inverter size to maximize financial return over the project term is determined taking into account the magnitude and financial value of inverter energy clipping, capital and on-going costs and other project financial parameters. This analysis demonstrates the value of inverter sizing to CPV rated power ratios at or close to 1:1 at CPV standard operating condition (SOC) rating (850W/m2 DNI, 20°C Ambient, On-Sun), or 1:1.25 at standard testing condition (STC) rating (1000W/m2 DNI, 25°C Cell). Concrete examples of how this methodology was applied to several commercial and planned SolFocus sites are presented.