Operation of PV Arrays at the Largest MPP Voltage Instead of the Global MPP Voltage during Irradiance Transitions Caused by Clouds

Abstract

Under non-uniform operating conditions, like partial shading, several maximum power points (MPPs) may exist on the electrical characteristic of a photovoltaic (PV) array and the global MPP may vary over a wide voltage range. When multiple MPPs exist, conventional MPP tracking algorithms can be trapped to operate at a local MPP instead of the global one, and consequently the energy yield of the PV array can be considerably reduced. The partial shading of well-designed large-scale PV power plants is mainly due to shadows of moving clouds. In this article, the operation of various PV arrays at the largest MPP voltage instead of the global MPP voltage has been studied during measured irradiance transitions caused by clouds. The voltage range of the MPP with the largest voltage was found to be clearly narrower than that of the global MPP and the energy losses resulting from the operation at the largest voltage MPP instead of the global one during cloud partial shading events were found to be slight. The results of this study justify the operation of PV arrays at the MPP with the largest voltage in lieu of the global one.