Researches On The Technology Of Solar Simulation By LED

Because of the distance between the sun and the earth, the atmosphere, the weather, the timeand the other factors, the spectrum and radiation intensity of natural sunlight is unpredictable.Solar simulator is an equipment used for simulating the radiation characteristics of the sunlight.Using the solar simulator, we can get the stable and controllable simulated sunlight in laboratory,and it is widely used in many fields, such as the space environmental simulation test of spacecraft,the measurement and calibration of solar cells, the aging test of construction materials and so on.At present, the artificial light source of solar simulator are mainly halogen and xenon lampswhose spectral distribution is close to the sunlight.But owing to the restriction of theirluminescent mechanism, there exist some defects, such as the low accuracy of matching thespectrum, the poor time stability, the complicated system structure, the high in price, the short lifeand so on.Based on the technical features of LED, such as the full spectrum, the stable and bettercontrolled, the wide controllable output range as well as the long life, et al, this paper usesmulti-led of different spectral power distribution to compose the surface light source andsimulates the sunlight by mixed spectrum of optical system. This method employs multi-groupprogram controlled constant current source to drive different LED arrays and makes the outputirradiance of simulated sunlight stable, reliable and adjustable rapid. By adjusting the drivecurrent of each LED array, we can get different distribution forms of output spectrum to meetdifferent demands of spectral matching degree in different areas. Using surface light sourceinstead of xenon lamp, we can greatly simplify the optical system and lower the manufacturingcost of solar simulator.Based on the demands of spectral matching degree of solar simulator,we construct the modelbetween LED drive current and light output, and the driving control model of LED solar simulatorby the numerical analysis method of LED spectrum; and then evaluate the performance ofverification facility of LED solar simulator, also by using the facility and program controlledelectronic load and the other measuring devices, to proceed the experiment of extracting theparameters of the solar cell model. The result of the test proves the technical feasibility of usingLED as the artificial light source of the solar simulator. The concrete contents are as follows:(1)The numerical model of LED spectrumAccording to the fact that the luminescent mechanism of LED is complicated and itsspectrum presents non-linearity, this paper proposes a numerical analysis method of LEDspectrum which is based on T-S fuzzy modeling: Firstly, an adaptive potential function clustering is designed to identify the structure of T-S model for LED spectrum ,and the recursive leastsquares method is used to identify the parameters of the model; Secondly, we introduce a chaosparticle swarm optimization algorithm(CPSO) to optimize the T-S model of LED spectrum. Theexperimental results of numerical analysis of LED spectrum indicate that the constructed modelof LED spectrum has a high fitting precision, the characteristic parameters of LED,such as theirradiance,the peak wavelength, the half-wave width and the color temperature , reflect theconsistency between the model of LED spectrum and the measured LED spectrum.(2)The model of LED drive current and light outputTaking the low power blue LED and the high power warm white LED as the experimentalobjects,and using the test and analysis system of LED spectrum, the sample data of T-S fuzzymodel parameters of LED spectrum under different drive current is obtained based on thenumerical method of LED spectrum. Through using this data set as modeling samples of themodel of LED drive current and light output, the relation model between the T-S fuzzy modelparameters of LED spectrum and the drive current is constructed by adopting the regressionstatistical methods, also proceeds with the regression test of significance by using the F-test, thecorrelation coefficient and the residual standard deviation.At last, this paper proceeds with the testand calibration of the relation model between LED drive current and light output by using theactual measured test sample of LED spectrum. The experimental results indicate that the relationmodel between LED drive current and light output can estimate the T-S fuzzy model parametersof LED spectrum under different drive current.With the estimated modeling parameters, the LEDspectrum can be calculated, and its half-wave width, the color temperature and the irradiancewhich are the characteristic parameters of LED spectrum reflect high consistency with thecorresponding parameters of the actual measured spectral curve of LED.(3)The driving control model of LED solar simulatorThe light which LED emits is incoherent, so the light output of the LED solar simulator is amulti-set of a linear superposition of LED light. Based on the relation model of LED drive currentand light output, we can get the driving control model of multi-LED solar simulator: the modelcan reflect the relationship between LED drive current of each group and the light output of LEDsolar simulator; also it can provide the working parameters for the LED constant current drivingsource. Based on the relation model of LED drive current and light output, this article designs afitness function which can comprehensively reflect the fitness of output irradiance of the sunlightand spectrum, and uses the chaos particle swarm optimization algorithm to solve the parametersof driving control model of the multi-LED solar simulator in order to adjust and control the outputirradiance of LED solar simulator.In the progress of actual modeling, considering the maindistribution area of LED spectrum, the output range of output power, the procurement of existing LED market, the existing laboratory instruments and equipments and the other factors, we choosethe high power warm white LED, the high power cold white LED, the low power blue LED andthe low power red LED as modeling and experimental objects.the driving control model of LEDsolar simulator are obtained which can realize to simulate the spectrum of visible light and adjustand control the output irradiance. The modeling experiment results indicate that in the visibleband and different output irradiance, the surface light source which is composed of multi-LEDcan meet the demand of the fitness of spectrum of solar simulator and this article verifies thefeasibility of using multi-LED as the artificial light source of the solar simulator.(4)The evaluation of verification facility and the experiment of extracting the parameters ofthe solar cell modelWe briefly describe the basic principle and composition of the verification facility of LEDsolar simulator, and evaluate the main performance parameters of this facility, such as the sunlightspectral match, the irradiance, the unevenness of irradiation space, the instability of irradiationtime and so on. a method is presented to extract the parameters of the solar cell model based onchaos particle swarm optimization algorithm: with the verification facility of LED solar simulatorand program controlled electronic load and the other measuring devices, we obtain the measureddata of the I/V characteristic curve of the solar cell, and use the chaos particle swarm optimizationalgorithm to extract the parameters of the solar cell model.