Study On Status Assessment And Hot Spot Of Photovoltaic Modules Under Partial Shading Based On Characteristic Calculation

New energy technology and large-scale use of clean energy are the latest trends in the study of energy science and technology in the world.As a clean and pollution-free form of new energy power generation,photovoltaic power generation has attracted extensive attention of researchers in various countries.Distributed photovoltaic power plants have become one of the main forms of photovoltaic power generation.Comprehensive fault diagnosis of distributed photovoltaic power plants is of great significance to improve power generation efficiency and reduce resource waste.In this paper,the external output characteristics of PV modules under fault status and the calculation method of internal parameters are synthesized,and the specific and feasible quantitative diagnosis process of PV modules’ hot spot fault is put forward.Specifically as follows:Firstly,in order to solve the problem of incomplete I-U data of photovoltaic modules in multi-peak state,a five-parameter calculation method of solar cells based on limited range data is proposed.Experiments on different materials and scales of solar cells in different power generation states are carried out to verify the reliability of the parameter calculation method.Secondly,according to the forward and reverse output characteristics of solar cells,the output characteristics model of the solar cell series circuit under partial shading condition is established,and the disciplination of the output characteristics is obtained.Combining with the physical meaning of the internal parameters of the model,the state evaluation characteristics are determined,which can describe the area and degree of shading condition,and the corresponding calculation method is given.By building a small photovoltaic power generation system,the experiment proves the validity of the output characteristic model of solar cell series circuit under partial shading condition and the reliability of the calculation method of state evaluation characteristic.Finally,concidering the structure of PV module,which is combined with the series-parallel structure of solar cells and bypass diodes,the output characteristics of PV unit in the module under partial shading are analyzed,and the mechanism of the formation and evolution of hot spots is studied.Based on the calculation of state evaluation characteristics and five parameters of solar cell,the fault diagnosis process of the module hot spots is proposed.The feasibility of the hot spot diagnosis method is verified by building a Simulink photovoltaic power generation simulation system.