Extended Boost PV inverter topology for the reduction of common-mode leakage current in three-phase applications

Abstract

Photovoltaic (PV) inverters must not generate high levels of common-mode (CM) ground leakage currents, which may flow due to fast variations in their CM voltage. Moreover, a highly desirable feature for PV inverters is their voltage step-up capability, which enables operation with lower DC input voltage levels, thus extending energy harvesting over wider solar irradiance and temperature ranges. This paper presents a new three-phase Boost PV inverter topology and its modulation strategy, designed based on a new concept for suppressing CM leakage currents in three-phase PV inverters. In contrast to past-proposed three-phase step-up topologies, the proposed PV inverter uses a modified Boost converter instead of a transformerless inverter, as well as a modulation strategy generating high-quality PWM voltage. Due to their combined characteristics, the variation of the CM voltage generated by the proposed PV inverter is minimized, which radically improves its CM current suppressing capability. The structure and operating principle of the proposed topology are presented, and its effectiveness with respect to CM current suppression is demonstrated through simulation results in MATLAB/Simulink.