A Brief Review on Single Phase PV Micro-Inverter System

Abstract

This paper presents a review on recent developments and a summary of inverter technology for single phase grid-connected photovoltaic (PV) systems for power levels up to 5 kW. The functions of inverter include DC–AC conversion, output power quality assurance, various protection mechanisms, and system controls. PV inverters are classified in three categories which are centralized inverter, string inverter and module oriented or micro inverter. Centralized inverter, string inverter and module oriented/integrated inverters are discussed as they are widely used in industrial applications. Based on discussion about these PV inverters, the limitation of centralized and string inverter came out. Centralized inverters have very large central inverter which also includes the large numbers of PV panels joined into series. This structure will produce high voltage. String is made up of PV modules by connecting them in series. Output of the string is then given to an inverter. Overall efficiency is improved compared to centralized inverter method and also there is reduction in size. In module oriented inverter/micro inverter, every solar panel unit has its private inverter. The integration of inverter and solar panel significantly decreases installation costs. It also maximizes the solar energy harvesting and improves safety. When some part of solar panel is covered by shadow of pole, tree etc. then centralized and string inverters can’t work. Micro inverter is cost efficient and effective solution when some panel is partially covered by shadow of tree, poles or tall building. Micro inverter is the best inverter topologies for solar PV module.

Keywords: PV inverters, single-phase micro-inverters, single-stage inverters, multiple-stage inverters