Plant Clipping Bias Due to Spatial Distribution of Inverters and AC Overbuild: Preliminary Investigation

This study investigated the bias in modeled generation for plants with a level of ac overbuild, that is greater aggregate inverter rated capacity than the plant’s grid export limit. The bias was simulated using operational data from two utility scale plants (20 MW and 200 MW). We found daily biases as high as 5% for a single variable day, while clear days experienced virtually no bias. Annual bias for the plants tested is estimated between 0.3-0.7%. In the annual case, the larger 200 MW plant was observed to have a lower bias for comparable overbuilding ratios, which we attribute to the larger inverter footprints for this plant. The use of operational data proved somewhat limiting, as it prevented a fully parameterized investigation of the issues. Further study is warranted to evaluate these effects on plants with different sizes and subject to different climatological conditions.