Grid connected, transformer less single phase inverter topologies for photovoltaic systems

Abstract

In order to provide safety to users, the design of a majority of the photovoltaic (PV) systems is made with galvanic isolation and with transformer. During conversion stage’s overall frequency is decreased because the transformer is expensive, heavy and bulky. The general efficiency of PV inverters with transformers ranges approximately from 92% to 94%. Therefore, a more effective, inexpensive, lighter and smaller PV system without transformer is introduced for managing such issues. For inverters without transformer, several kinds of configurations, such as dual parallel buck inverter, oH5, HERIC, H5, H6, etc., are available. However, several disadvantages, such as MOSFET reverse recovery issues, dead time necessities at the grid voltage’s zero crossing instances (for the avoidance of grid shoot-through by faults), shoot-through by switch issues, and high conduction losses, are associated with such configurations. Two problems are associated with the proposed inverter without transformer. The first problem is that in order to attain a higher efficiency, super junction MOSFETs (CoolMOS) have to be utilized for all switching devices. The second problem is that no shoot-through problems must be experienced by the inverter’s configuration for attaining a higher reliability. A detailed analysis of the entire above transformerless inverter with simulation results obtained from Simulink is presented in this paper.