Impact of inverter DC to AC ratio on soiling losses and cleaning intervals in large solar PV plants

Abstract

Clipping is a phenomenon in solar photovoltaic (PV) plants where the inverter output becomes constant after reaching its maximum limit, typically when the inverter is undersized compared to the PV array. While clipping generally causes energy loss, it can help reduce additional losses during soiling by naturally limiting peak power. This study investigates the potential to optimize clipping to maximize operational profits by balancing soiling losses and clipping losses. Instead of directly minimizing clipping loss, a minimum cleaning interval is imposed as a constraint. An algorithm is proposed to determine the maximum allowable clipping, expressed as the Inverter Loading Ratio (ILR), for different soiling rates (SRT) while maintaining the minimum cleaning interval. The approach is validated using the specifications of a 10 MWp PV plant near Madurai, Tamil Nadu, India, with a daily SRT of 1 % and a minimum cleaning interval of 15 days. Results show that a higher ILR allows more soiling, while a lower ILR allows less. An optimum ILR of 1.39 delivers the highest benefit, yielding an annual net gain of €3600 by subtracting clipping related loss of revenue (LoR) from the combined cost of cleaning (CoC) and reduced LoR due to soiling loss.