Reserch On Leakage Current Suppression Of Non-isolated Module Cascade Single-phase Photovoltaic Grid-connected Inverter

China is a large energy-consuming country.With the depletion of fossil energy and the negative impact of its large-scale use,the development and utilization of clean solar energy resources has become an inevitable way.Non-isolated module cascaded single-phase photovoltaic grid-connected inverter as the core of solar photovoltaic power generation gridconnected,with its unique advantages will have a very wide range of applications.However,the non-isolated structure will flow a large leakage current on the stray capacitance formed between the photovoltaic panel and the ground,thereby endangering the safety of life.Therefore,solving the problem of leakage current of cascaded single-phase photovoltaic gridconnected inverters with non-isolated modules has become a major research topic.At present,domestic and foreign research scholars have done a lot of work,and there are still many shortcomings while achieving many results,so the subject still needs further analysis.Before analyzing the leakage current of non-isolated module cascaded single-phase photovoltaic grid-connected inverter,this paper first analyzes the causes of leakage current.Taking the non-isolated single-phase H-bridge inverter without cascade as an example to establish its high-frequency common-mode equivalent model,the factors that affect the magnitude of leakage current are obtained through analysis,so as to obtain the sources of three conventional leakage current suppression schemes.The low-frequency common-mode equivalent model is also established,and the expression of the stray capacitance terminal voltage is analyzed to facilitate the conclusion of the test.Then,it analyzes the implementation principle,leakage current suppression effect,advantages and disadvantages of the above suppression schemes,and summarizes an analysis method suitable for the leakage current suppression of the traditional two-level to three-level non-isolated single-phase photovoltaic grid-connected inverter.Then the above analysis method is extended to the analysis of module cascading topology.Taking a five-level non-isolated single-phase cascaded H-bridge photovoltaic grid-connected inverter as an example,this method is used to analyze the reason why this topology cannot suppress leakage current.By comparing with the ordinary H-bridge topology,it is difficult to obtain the leakage current suppression of the cascading topology of the module.Based on the above analysis,this paper proposes a non-isolated single-phase cascade dual-buck photovoltaic grid-connected inverter based on DBI topology and cascaded H5 topology.Through modal analysis and establishing its equivalent model,it is concluded that the proposed inverter modulation strategy can meet the conditions of leakage current suppression and has good leakage current suppression capability.Then,the simulation is established on the MATLAB / Simulink platform,and the simulation results fully conform to the conclusion of theoretical analysis.Finally,build an experimental platform for experiments.By comparing the experimental results with theoretical analysis and simulation results,the above conclusions are further verified.