A high efficiency and high reliability single-phase modified quasi Z-Source inverter for non-isolated grid-connected applications

Abstract

Quazi Z-Source inverter (qZSI) is a promising inverter topology that can buck or boost input voltage without a DC-DC converter and hence can be used in transformerless configuration. This is a high efficiency solution because of single stage processing and conversion. In this paper a novel modified qZSI topology is proposed and new modulation technique is presented to reduce common mode leakage current that is generally present in non-isolated transformers feeding utility grid. The proposed inverter offers a, high efficiency and a high reliability solution in a single-phase solar photovoltaic system for grid integration. Presented topology, (1) uses phase-leg shoot through for boosting the DC voltage to the required level which eliminates the additional DC-DC converter, (2) eliminates the PWM dead-time and provides freewheeling through additional switches (smoothens output AC grid current), (3) minimizes leakage current, (4) avoids body diode conduction for main devices increasing the efficiency of the system because body diode have poor reverse recovery characteristics, (5) effectively utilizes magnetic components, (6) common mode leakage current will be reduced to 0.2% of the rated current which is negligibly small. Simulation and experimental results are verified for a 120V (peak), 15A (peak) at 0.99pf.