Impact of overloading of photovoltaic arrays on the evaluation of photovoltaic power generation forecasts

Photovoltaic power generation (PV output) forecast is based on solar irradiance forecasts; therefore, an increase in overloading of PV arrays may affect errors in the PV output forecast. To study the impact of overloading of PV arrays on evaluation of PV output forecasts, we compared the estimated and forecasted values of PV output under various overloading conditions and investigated the characteristics of forecast errors resulting from overloading. We used data of actual estimated PV output and forecasted PV output for 2016 to calculate the estimated and forecasted values of overloaded P PV output. Our findings indicate that compared with over-forecasted errors, errors due to under-forecasting undergo higher reduction in both time and magnitude with increasing inverter loading ratio. However, contrary to the initial assumption, the effect of PV module overloading was smaller than expected, which could be attributed to the smoothing effect of PV systems in a large area. PV module and array prices have been decreasing in the long term, and the number of overloaded PV systems is expected to increase worldwide. This study provides useful information for the stable operation of power systems including overloaded PV systems and for improving the economics of PV systems.