Modulation for three-phase transformerless neutral point clamped inverter in photovoltaic systems

Abstract

In this paper is proposed modulation techniques for reducing leakage current in grounded photovoltaic panels for three-phase transformerless neutral point clamped inverters, which appear if there is no galvanic isolation between the photovoltaic system and the electric grid. The control is done by applying appropriate pulse width modulation techniques, that are capable of reducing the leakage currents in photovoltaic systems by applying three medium vectors or using only two medium vectors and one specific zero vector to compose the reference vector. To validate the simulation models, an experimental three-phase inverter is used to evaluate leakage currents and the dc link voltage control. © 2011 IEEE.