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

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.

Keywords

• Step up
• dc-ac
• common ground
• photovoltaic system