DC/AC Conversion Topologies for Photovoltaic Applications

Abstract

The evolution of DC/AC conversion configurations for Photovoltaic (PV) applications started from the central inverter, string inverter, DC optimizer with central inverter to the microinverter. The evaluation of each configuration efficiency is a main concern due to the rising dependence on PV power plants. Besides, the fact that uneven solar irradiance levels and modules mismatch play an important role in defining the system efficiency. This paper compared the efficiency of the DC/AC conversion configurations: the string inverter, the DC optimizer and the microinverter. The efficiency was estimated based on the maximum power point tracking efficiency, power electronics stage efficiency and cable losses, where all of them were combined to estimate the configuration efficiency. SIMULINK was used to model each configuration and estimate the efficiency. The model main input was the solar irradiance of different shading patterns. The results showed that the microinverter has the highest efficiency at all shading patterns. However, at some patterns of irradiance levels, it competed with the DC optimizer configuration where they have close efficiencies. The string inverter results showed it significantly depends on the irradiance pattern where its efficiency can vary between 15%-95%.