Research And Design Of Photovoltaic Cell Module Test System

With the development of economy,the problems of energy and environment have become increasingly serious.As a clean and renewable energy,solar energy is of great significance in changing the energy structure and improving the ecological environment.The photovoltaic cell module directly converts solar energy into electric energy,and the photovoltaic cell module test system is a piece of equipment for judging the performance of the battery module.The traditional test system has problems of low accuracy,single measurement range,and high cost,and cannot give five parameters that characterize the internal characteristics of the battery.The thesis studies the development status of photovoltaic cell test technology,improves the traditional photovoltaic cell module test system by designing an electronic load testing method based on voltage feedback and solves five parameters representing the internal characteristics of batteries by an analytical algorithm.The photovoltaic cell module test system designed in the thesis has high precision and multiple measurement ranges.The main research subjects of this thesis are detailed as follows.The thesis analyzes the working principle and equivalent circuit of photovoltaic cells.A new modeling method with Matlab/Simulink of photovoltaic cell module based on complete I-V equation is proposed in this thesis.The model simulates the theoretical output curves of battery modules using nameplate parameters under different conditions,which provides a basis for verifying the testing curves.Through the analysis of testing methods,the overall design scheme of the system based on variable electronic load is proposed.The thesis carries out hardware design according to the functional requirements of the test system,including the design of solar simulator,electronic load module and data acquisition circuit.The precise control of the irradiance is realized by designing the feedback loop of the irradiance.Aiming at the shortcomings of open-loop control for electronic load in traditional test system,an improved voltage feedback electronic load circuit is designed in this thesis.In view of the single-range measurement of the traditional system,a multi-range voltage and current measurement circuit is designed in this thesis.The thesis completes the software design of the test system,including data acquisition program,serial communication program,I-V curve fitting algorithm and parameter solving algorithm design.With piecewise and variable step-size collection,the data acquisition program performs non-uniform and efficient sampling of the I-V curve of the photovoltaic cell module.The 9-degree polynomial fitting method with high precision is used to fit the measured I-V data,and the modified analytical algorithm is used to obtain five characteristic parameters of photovoltaic cells.Finally,the thesis builds a system testing platform and conduct experiments on the solar simulator and standard battery modules to verify the feasibility of the photovoltaic cell module test system designed in the thesis.The photovoltaic cell module test system designed by the thesis has high measurement accuracy.The test system can measure various specifications of battery components and solve five parameters that characterize the internal characteristics of the battery,having wide application prospects.