Single-Phase Five-Level H5 and HERIC Transformerless Inverters for PV Applications

Abstract

This work proposes an improved single-phase five-level H5 and Heric transformerless inverter topologies for grid-tied photovoltaic systems. The suggested topologies overcome issues associated with standard transformerless inverter topologies such as three-level operation, the influence of switch junction capacitances, and the lack of a bi-directional current path. Additional bi-directional clamping branches and modified modulation technique enables the inverter to operate under different power factor conditions of the grid without increasing the total harmonic distortion (THD) and common mode currents (CMC). Moreover, the proposed topologies generate five-levels in the output which will further reduce the THD and size of the passive components. Performance evolution between the traditional and proposed topologies was carried-out using 1 kW test setup implemented in PSIM simulation software using thermal module tool set.