Performance Analysis of a Hybrid Three-Level/Two-Level Inverter for Renewable Energy Systems: NPV Balancing, Dead Time and Leakage Current Suppression

Transformerless grid-connected photovoltaic (PV) systems face significant challenges, including common-mode voltage (CMV) and leakage current, which distort the grid-injected current, increase system losses, and generate undesired electromagnetic interference. This article presents a comprehensive analysis of a three-phase hybrid three-level/two-level (HTL2) inverter to address these issues while reducing the number of required semiconductor switches. The self-balancing of the neutral-point voltage (NPV) is mathematically and experimentally validated for both balanced and unbalanced loads. Furthermore, a novel duty cycle adjustment is proposed to maintain precise NPV balance in the presence of dc current components. The theoretical impact of dead time (DT) effects on inverter performance is analyzed and the pulsewidth modulation has been modified to consider the impact of the DT on CMV. Extensive simulations and experimental validation confirm the effectiveness and reliability of proposed control approaches of the hybrid inverter in achieving NPV balancing, DT managing, and leakage current suppression.