A Common-Ground Single-Phase Five-Level Transformerless Boost Inverter for Photovoltaic Applications

This paper presents a transformerless five-level boost inverter with common ground connection for single-phase photovoltaic (PV) systems. It consists of nine switches, two capacitors, and an LC filter at the output. The topology eliminates common mode (CM) leakage current by connecting the negative terminal of the PV directly to the neutral point of the grid, which bypasses the PV array's stray capacitance. As compared to the conventional flying capacitor (FC) multilevel inverter and the cascaded H-bridge (CHB) multilevel inverter, the proposed topology achieves an output voltage that is up to four-times higher given an equivalent dc-link voltage. This reduces the dc-link voltage requirement to one fourth of the values used in conventional multilevel inverters (FC, CHB, NPC, ANPC) and one half of the conventional H-bridge topologies. The following manuscript presents the operation principles and theoretical analysis of the proposed topology, which are supported by simulation and experimental results. A 1 kW prototype was constructed; it achieves 96 % efficiency operating at an output of 240 V-AC, 60 Hz, and 973 W.