A Research On PV Hot Spot And MPPT Under Non-uniform Insolation

Fossil energy is becoming scarce so that nonrenewable resources—solar energy occupiesa place in energy market, and becomes more and more popular. Relative researches of PVsystem have been an important issue in the field of nonrenewable resources. At present, theconversion rate of commercial PV module is still low, only 15%～17%, and price is high. It islong to earn back the cost, leading to some effects on the popularity of using solar energy. Inthis case, it is very important to prolong the lifetime of PV module and try best to make gooduse of the power generated from PV module. So, this paper mainly focuses on the researchesof Hot Spot that may damage PV module and the maximum power point tracking (MPPT)under non-uniform insolation.Build simulation model of PV cell and PV module basing on the PSpice software and theequivalent circuit of PV cell, then obtain I-V curve of PV cell and PV module with one cellshaded under different shade rate. And we can also obtain the voltage-changing curve of PVcell. Base on these, we can analyze the theory of Hot Spot and propose the possibility andconditions of causing Hot Spot in low-voltage and high-voltage systems. We also propose theoptimal PV cell number for paralleling with one bypass diode.In addition, when PV module or PV array is under non-uniform insolation which can leadto Hot Spot, the output I-V curve may be in ladder shape, and its corresponding P-V curvecontains several local maximum power points so that the current single-summit PV cellmathematic model and single-summit maximum power tracking algorithm can not work anymore. Therefore, this paper does some researches to build multi-summit PV module that canwork under non-uniform insolation. Then build its corresponding computer simulation modelin MATLAB. Basing on the multi-summit model, we can design a multi-summit MPPTalgorithm that can work under uniform insolation and non-uniform insolation. Throughsimulation experiments in MATLAB, it is proven that this multi-summit MPPT algorithm canwork well in uniform and non-uniform circumstances successfully and have relative hightracking efficiency.Finally, according to the knowledge of Power Electronics, build a computer model ofMPP (Maximum Power Point) tracking system by MATLAB/Simulink. Then compute major parameter values of the circuit. And through the simulation tests in MATLAB, the circuit ofMPP tracking system was built successfully.