Research On Electromagnetic Infrared Thermography Defect Detection Technology Of Silicon Photovoltaic Cell

With the rapid growth of photovoltaic industry in China,higher requirements for quality detection of silicon photovoltaic cells are also put forward.Silicon photovoltaic cell is the core device of photovoltaic power generation.Its quality directly affects the efficiency of photovoltaic modules.In photovoltaic cells,the existence of defects will greatly reduce the efficiency,reliability and service life,and even influence the stability of photovoltaic systems.Therefore,defect detection,failure analysis and damage monitoring of silicon photovoltaic cells have important research significance.The purpose of this thesis is to develop a non-destructive testing method for silicon photovoltaic cells based on electromagnetic induction,which can meet the needs of non-contact,rapid,high resolution,high sensitivity,multi-parameter evaluation and quantitative detection.The specific method is to use short wave infrared camera and infrared thermal imager for high resolution and high sensitivity measurement and imaging of the light radiation and thermal radiation produced by the photovoltaic cells and modules due to electromagnetic induction.The integrated processing and image fusion of light and thermal radiation signals can be used to detect and overall health of silicon photovoltaic cells and modules.The main research contents and innovation points are as follows:Firstly,the modification of electro thermography and electroluminescence(EL)detection by electromagnetic induction(EMI)is studied.On the basis of studying the principle of ET and EL detection,the interaction mechanism of eddy current heat,heat conduction,heat radiation,electroluminescence,photon radiation and other physical processes has analyzed.It is proposed to integrate electro thermography and electroluminescent technology,and to enhance the detection effect by electromagnetic induction.Secondly,the detection technology of electromagnetic induction thermography is studied.A digital electromagnetic induction thermography system is established.The thermography sequence of silicon photovoltaic cell is obtained under pulse and lock-in mode.Fast fourier transform(FFT),independent component analysis(ICA),principal component analysis(PCA)and other methods are used to deal with thermography sequences.Finally,the visual inspection of hot spot,crack,broken gate and heavy doping in silicon photovoltaic cells has realized.Thirdly,image fusion technology of thermography and electroluminescence is studied.An adaptive image fusion algorithm based on sparse representation(SR)is proposed.First of all,two groups of sparse coefficients are obtained by using the orthogonal matching pursuit(OMP)algorithm based on the sparse dictionary trained.Then the fusion rules are selected adaptively according to the sparse feature,thus the sparse coefficients of the fused image are obtained.Finally,the fused image is reconstructed by combining sparse dictionary and fusion coefficient.In the fusion process,sparse representation is used to remove the noise very well.A fused image with clear defect characteristics of silicon photovoltaic cells is obtained.Experimental results show that the algorithm is better than other two algorithms and achieves better fusion results.