DC collector grid configurations for large photovoltaic parks

This paper presents a theoretical efficiency comparison among the conventional ac collector grid configuration and two proposed dc collector grid configurations (one with string-pair-level maximum power point (MPP) tracking and one without) in large photovoltaic (PV) parks. A typical sunny day in September is used as a test case to determine the PV array yield. An already validated PV array performance model is used to estimate the expected yield of the PV array for the given environmental and connection conditions. Loss mechanisms in different grid components in the three configurations are discussed and simplified loss models are developed without compromising the accuracy. These components include the inverters, transformers, ac/dc cables and dc-dc converters. The chosen figure of merit is the total efficiency of the components lying between the PV array and the MV/HV transformer that feeds power in the HV grid. A comparison of the total losses helps to identify the configuration that has the potential to operate at higher efficiency and hence, generate more revenues.