A Eleven Level Grid Connected Transformer Less PV Systems

Abstract

This paper presents a single-phase transformer less grid-connected photovoltaic converter based on two cascaded full bridges with different dc-link voltages. The converter can synthesize up to eleven voltage levels with a single dc bus, since one of the full bridges is supplied by a flying capacitor. The multilevel output reduces harmonic distortion and electromagnetic interference. A suitable switching strategy is employed to regulate the flying-capacitor voltage, improve the efficiency (most devices switch at the grid frequency), and minimize the common-mode leakage current with the help of a novel dedicated circuit (transient circuit). Simulations and experiments confirm the feasibility and good performance of the proposed converter.