A Non-Isolated Step-up DC-AC Converter With Reduced Leakage Current for Grid-Connected Photovoltaic Systems

Xuefeng Hu,Yujia Zhang,Laian Mao,Zhixiang Yu,Xing Liu,Tianya He

doi:10.1109/access.2020.2986605

Abstract

In this paper, a non-isolated step-up single-phase dc-ac converter is proposed for distributed low voltage photovoltaic (PV) systems. The proposed converter has a common ground between the dc photovoltaic input and ac output voltage, which can reduce the leakage current to a very low level and thus improve the reliability and power generation efficiency. By analyzing and comparing the two modulation methods, a unified half cycle modulation is selected for the design of the proposed converter, in which only two switches are operated at high frequency in a line cycle. Therefore, the conduction and switching loss can be reduced greatly. In addition, due to the unified half cycle modulation for the active switches of the proposed inverter, the dc-link capacitor does not need to have a decoupling function. The capacitor can then be optimized to a small value for improving the reliability and power density. A theoretical analysis of the proposed converter is described, and an experimental prototype is implemented to verify the performance of the presented converter topology.

Highlights

Grid-connected dc-ac converters play an increasing important role in distributed photovolatic (PV) generation systems, in which the dc-ac converters are used to feed the PV power into the utility grid
The PV inverters with high frequency transformers have the advantages of low cost and small size
EXPERIMENTAL RESULTS A prototype converter is built to verify the effectiveness of the proposed topology

Summary

INTRODUCTION

Grid-connected dc-ac converters play an increasing important role in distributed photovolatic (PV) generation systems, in which the dc-ac converters are used to feed the PV power into the utility grid. In order to overcome the disadvantages of the aforementioned classic circuits, some new common-groundtype step-up PV inverters are proposed in recent literature works [17]–[22] These topologies eliminate leakage current by connecting the negative terminal of the PV directly to the neutral point of the grid. They used more switches, which can result in higher conduction losses and a larger size.

CIRCUIT CONFIGURATION AND ANALYSIS

VOLTAGE GAIN ANALYSIS

CONCLUSION