Research On Global MPPT Control For PV System Based On Modified Grey Wolf Optimization And Golden-Section Optimization

With fossil energy resource gradually depleting and the expectation for a better ecological environment increasingly growing,vigorously developing clean energy and other renewable energy technologies have aroused widespread concern around the world.Among various kinds of renewable energy,solar energy has already been extensively promoted worldwide because it is abundant,inexhaustible and environment-friendly.In order to improve the efficiency of photovoltaic generation and then reduce cost indirectly,maximum power point tracking(MPPT)control technique is indispensable.Photovoltaic generation equipment is usually built in open and sunny outdoor environment,and large-scale photovoltaic array is composed of dozens or even hundreds of photovoltaic panels in series and parallel.Such a large-scale photovoltaic array would inevitably shaded by clouds,dust and so on,which causes that the output characteristic curve of PV array exhibits multiple local optimums.The problem that MPPT control technique needs to solve is how to quickly and accurately track the global maximum power point(MPP)so as to improve the efficiency of photovoltaic generation system.Based on the analysis of background and significance of photovoltaic power generation,this paper introduces and expounds several classical MPPT control algorithms.And the output characteristic curves of photovoltaic array under uniform illumination and partial shading conditions are simulated and analyzed by using MATLAB/Simulink.Under partial shading conditions,multiple peaks would appear on the output characteristic curve of photovoltaic array.However,conventional MPPT algorithms are possible to immerse in a local MPP because they are unable to discriminate local MPPs and the global MPP.In order to solve this problem,this paper presents a hybrid control algorithm based on modified grey wolf optimization(MGWO)and golden-section optimization(GSO).Firstly,the MGWO algorithm is activated for the global search to search approximate location of the global MPP.On the basis of previous search,the GSO algorithm is used for local search.The proposed algorithm adopts different control strategies in different stages for achieving the coordination between global search and local search.Additionally,aim at the issue that traditional restart judgment method is possible to be invalid,this paper introduces a novel restart judgment based on the quasi-slope of the power-voltage curve to enhance the reliability of MPPT systems.Finally,the MPPT simulation platform based on Boost circuit is built in MATLAB/Simulink,and the hardware experiment platform based on TMS320F28335 is designed and constructed.Simulation and experiment results demonstrate that the proposed algorithm can immediately and accurately track the global MPP under partial shading conditions and can improve the efficiency of photovoltaic system.