| The photoelectric conversion efficiency of photovoltaic cells is low presently and the output power is more restricted by ambient temperature and light intensity.For improving comprehensive efficiency,the excellent MPPT(Maximum Power Point Tracking)control strategy should be used between PV cells and the external load.On the other hand,due to external periodic climate condition,there is a close relationship among the PV output power quality and environmental conditions such as the seasons,day and night.To ensure the stable and reliable operation of electrical load,it is necessary to introduce the external power to provide supplementary energy for photovoltaic power generation systems.First,this paper introduces the working principle of photovoltaic cells and establishes its mathematical simulation model in Matlab to analyze its P-Uoutput characteristic curve.Then,the advantages and disadvantages of the three kinds of common MPPT control strategy are analyzed,the MPPT control algorithm of dual mode incremental conductance method based on the initial value setting is proposed in this paper.During the mathematical deduction of the proposed algorithm,the relationship between the photovoltaic battery open circuit voltage Uoc and light intensity S and the impact on the speed of MPPT control program based on the reference voltage initial value setting are analyzed.This paper has designed the hardware realization circuit and simulated experiment,contrast experiment in indoor environment and application experiments in outdoor environment.Next,to make up for the defects of off-grid photovoltaic power generation system,this paper designs the photovoltaic-grid hybrid power system,then show the structure of hybrid power system and switch control circuit,Finally,the control strategy has been carried on the experiment under the resistant perceptual load.The experiment and evaluation results show that:(1)Under the condition of the computer simulation,the tracking time of the proposed MPPT algorithm is 0.27 s and 0.15 s respectively,and the tracking efficiency MPPT is 98.72% when light intensity changes twice.Compared with the PV system without control strategy,the percentage of energy increase MPPT is 6.09%,the simulation has verified the true of the proposed algorithm.(2)Under the controlled environment indoors,compared with not exert control strategy,the MPPT of PV system is 3.90%,and the tracing efficiency MPPT is 95.69% in the weak light;the MPPT of PV system is 3.72%,and the tracing efficiency MPPT is 97.83% in the strong light.Exerting control algorithm,the track time increased by 0.98 s and the MPPT is 3.67%,and the chase ensemble efficiency MPPT is 95.87%,the proposed algorithm has the strong environmental adaptability and reduces the steady-state oscillation of the system in environment mutation condition.(3)The results of cross-over design trial under theoutdoor actual environmentshow that the proposed MPPT control strategy in this paper has achieved good results in the photovoltaic system startup performance test,the dynamic performance test and performance test load mutation case,the results show that tracking time is reducted and the anti-jamming ability is enhanced.The proposed MPPT control strategy has a certain guiding significance in engineering application.(4)Photovoltaic-grid hybrid power system is designed and construction in this paper,the experiments show that the hybrid power system can realize the stability of power switching,the switching time isless 0.7seconds and it accordances with the national standards of GB/T14048.11-2002[The automatic switch electrical appliances].Last,the operation efficiency of hybrid power system is analysised in paper. |
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