Research On Leakage Current Suppression Method For Single-Phase Non-Isolated Photovoltaic Grid-Connected Inverter

Non-isolated photovoltaic grid-connected inverters have been researched more and more because they have eliminated the transformer and have the advantages of small size,light weight and simple structure.In the non-isolated inverter,there is parasitic capacitance between the solar panel and the earth,which will form a common mode loop with the earth,the power grid and the photovoltaic array,so that leakage current is generated,and the leakage current will affect the quality of the equipment and the incoming network current.Even personal safety brings harm.Therefore,whether the leakage current meets the standard is an important indicator for determining whether the non-isolated inverter can work safely and normally.This paper mainly studies the suppression of leakage current of single-phase non-isolated photovoltaic grid-connected inverters.Firstly,this paper takes a full-bridge non-isolated photovoltaic grid-connected inverter as an example,and analyzes the mechanism of leakage current generation and the common-mode loop model,and analyzes the suppression of leakage current under different modulation strategies.Simulation verification summarizes the ways to suppress leakage current.Secondly,under the unipolar PWM modulation strategy,the scheme of adding the common-mode inductor to suppress the leakage current of the full-bridge H4 inverter is analyzed and verified,which proves that it can be added without affecting the normal operation of the inverter.The common mode inductor provides a high impedance when the circuit is in the freewheeling phase,which effectively suppresses leakage current.This paper also combines the scheme of adding common mode inductor with the H5 and H6 topologies with the ability to suppress leakage current.It turns out that the two methods of suppressing leakage current do not conflict,and can complement each other when encountering harsh conditions.The inverter can be more protected against leakage current.Finally,this paper builds an experimental platform for non-isolated inverter based on DSP digital control.The experimental results prove the correctness of theoretical analysis and simulation research.