Research And Design Of Photovoltaic Controller Based On Multi-Peak MPPT Algorithm

With the depleting of non-renewable energy and the deteriorating of the environment,the search for renewable energy is the desire of all countries in the world.Photovoltaic(PV)system is recognized as one of the most promising ways of generating power in the future.PV controller is directly related to the utilization efficiency of photovoltaic cell,which is the energy source of PV system.The maximum power point tracking(MPPT)algorithm of PV controller is the foundation of improving efficiency.In this paper,based on the independent PV system,an improved Particle Swarm Optimization(PSO)MPPT algorithm was designed.Under the Simulink simulation toolkit,it showed that the algorithm had a good maximum power point tracking effect when the P-V characteristic curve of PV array has multiple peak points.Then,a PV controller based on two-phase staggered parallel sync Buck topology was designed.The controller adopted a 4-phase intelligent charging algorithm combined MPPT algorithm with battery charging characteristics.It also had a good humancomputer interaction experience and a series of safety protection.The detailed research contents of this paper are as follows:1)The status of PV system and MPPT algorithm were researched.Single PV cell was transformed into an equivalent mathematical model,so it could be showed in Simulink simulation environment that the output characteristics of PV cells were determined with the change of illumination and temperature.However,the P-V curve maintains the unimodal characteristic in different external environments.Then,the output characteristics of the PV array under local shading conditions were studied.Model of partial shading PV array were established and it was found that the output P-V curve of partial shading PV array had multiple peak points;2)Traditional single-peak MPPT algorithm was studied,and the failure analysis of the traditional algorithm in local shadowing environment was carried out.Through the further study of partial shading PV array model,an MPPT algorithm based on Improved Particle Swarm Optimization was designed and it was found to perform well.The algorithm also had dynamic tracking ability when the ambient light intensity changed;3)The hardware circuit of PV controller was designed in detail,including the main circuit based on two-phase staggered parallel Buck,power supply circuit based on Flyback conversion,control circuit based on STM32 Micro Controller Unit,two different kinds of human-computer interaction circuit,protection circuit and other peripheral circuits;4)The charging characteristics of the battery was studied,and the charging characteristic curve of the storage battery was divided into a four-stage auto-switching charging periods combined with the MPPT algorithm.The software of PV controller was designed in detail,including system initialization,system time base generation,intelligent charging program,charging protection and display interface program.PC software for experimental data acquisition was designed based on C # language;5)Experimental platform of PV system was set up and experiments had been carried out in five aspects as follows,power output performance,charging ripple index,MPPT effect,charging effect at all stages and charging quality.The experimental results showed that the designed PV controller can effectively track the Maximum Mower Point,it realized intelligent switching during the charging phase.The conversion efficiency of the circuit was over 97%.