A Single-Stage Quasi-Z-Source-Based 5-Level Grid-Tied PV Inverter With Reduced Leakage Current

Abstract

This article presents a single-staged quasi-z-source (qZS)-based 5-level inverter topology for grid-tied photovoltaic applications. In this topology, two symmetrical qZS networks with a single dc source are fused with a 5-level hybrid inverter. When compared to the existing qZS-based 5-level inverters in the literature, the proposed power converter employs fewer semicon ductor switching devices, enhancing its reliability. The objectives of boosting the voltage of the input PV source, as well as the synthesis of a 5-level output voltage are achieved with a modified level-shifted PWM scheme. Furthermore, closed-loop control schemes are implemented for the proposed power converter in both standalone and grid-tied modes of operation and its dynamic performance is assessed. The operability of the proposed power converter in the grid-tied mode of operation is demonstrated by injecting active power into the grid at the unity power factor (UPF). It is also shown that the proposed topology is capable of reducing the leakage current, which is one of the major safety concerns in transformerless PV systems. Experimental results obtained with a laboratory prototype, validate the operating principles of the power converter in both standalone and grid-tied modes of operation.