A Modified Single-Phase Transformerless Z-Source Photovoltaic Grid-Connected Inverter

- Journal title : Journal of Power Electronics
- Volume 15, Issue 5, 2015, pp.1217-1226
- Publisher : The Korean Institute of Power Electronics
- DOI : 10.6113/JPE.2015.15.5.1217

Title & Authors

A Modified Single-Phase Transformerless Z-Source Photovoltaic Grid-Connected Inverter

Liu, Hongpeng; Liu, Guihua; Ran, Yan; Wang, Gaolin; Wang, Wei; Xu, Dianguo;

Liu, Hongpeng; Liu, Guihua; Ran, Yan; Wang, Gaolin; Wang, Wei; Xu, Dianguo;

Abstract

In a grid-connected photovoltaic (PV) system, the traditional Z-source inverter uses a low frequency transformer to ensure galvanic isolation between the grid and the PV system. In order to combine the advantages of both Z-source inverters and transformerless PV inverters, this paper presents a modified single-phase transformerless Z-source PV grid-connected inverter and a corresponding PWM strategy to eliminate the ground leakage current. By utilizing two reversed-biased diodes, the path for the leakage current is blocked during the shoot-through state. Meanwhile, by turning off an additional switch, the PV array is decoupled from the grid during the freewheeling state. In this paper, the operation principle, PWM strategy and common-mode (CM) characteristic of the modified transformerless Z-source inverter are illustrated. Furthermore, the influence of the junction capacitances of the power switches is analyzed in detail. The total losses of the main electrical components are evaluated and compared. Finally, a theoretical analysis is presented and corroborated by experimental results from a 1-kW laboratory prototype.

Keywords

Common-mode voltage;Leakage current;Photovoltaic power system;Power loss;Pulse width modulation;Z-source inverter;

Language

English

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