Design of grid connected transformerless photovoltaic inverter for power system utility

Abstract

The transformer less PV inverter is more efficient compact and small in size In these methods the PV panels are directly connected with the grid It creates a conduction loop between PV panels to grid by parasiticcapacitance If the high frequency common mode voltage is not maintained constant in inverter operation then the large amount of high frequency leakage current is injected in this loop It affects the system performance by creating harmonic current power loss electric shock and electromagnetic interference Therefore the leakage current should be limited within certain level to comply with standards and improve the reliability of the systems Due to the circuit component imperfections and the absence of transformer a small amount of DC is always present in the inverter output This DC injection in to the grid creates the saturation problem of the distribution transformer associated with the grid resulting in overheating higher losses and poor power quality in the power system An Artificial Neural Network ANN controller is designed with back propagation algorithm to reduce the DC offset current injection in to the grid. The main contributions of the present investigation include Carried out simulation studies on different transformer less PV inverter topologies with the proposed transformer less PV inverter topology upto five level and discussed the performance of all the topologies with regard to ground leakage current minimization newline