Multi-Peak Photovoltaic System MPPT Control Based On ISFLA Strategy Research

Photovoltaic grid-connected power generation technology is developing rapidly.The two-stage photovoltaic grid-connected system is widely used in photovoltaic grid-connected power generation systems due to its flexible installation configuration and easy modularization.The traditional two-level grid-connected inverter has a large output voltage harmonic content,which seriously affects the stable operation of the power grid;the photovoltaic power generation utilization efficiency is low.Aiming at the requirements of the stability and high efficiency of photovoltaic grid-connected power generation system,this paper takes the two-stage grid-connected inverter system as the research object,and improves the structure optimization and efficiency improvement of the inverter.The main work of this paper is as follows.Firstly,the problem of the output voltage harmonic content of the grid-connected system is combined.Combined with the existing topological structure of the photovoltaic power generation grid-connected system and the output characteristics of the multi-level inverter,the five-level grid-connected inverter topology is selected.As an inverter in the grid-connected system.On this basis,the power loss of the semiconductor power device in the five-level inverter is calculated.The results show that the five-level topology can reduce the output voltage harmonic content and the loss of the switching device,and improve the overall conversion efficiency.Then,for the problem that the photovoltaic array suffers from local shadow,the utilization efficiency of photovoltaic power generation is low.The simulation model of photovoltaic cell is established in Simulink,and the multi-peak characteristic curve of the output is obtained.The pre-stage Boost circuit in the two-stage grid-connected system uses the improved shuffled frog leaping algorithm(ISFLA)multi-peak MPPT algorithm to control the duty cycle of the switching device to ensure global power tracking.At the same time,the speed and accuracy of tracking the maximum point of global power can be improved.Finally,according to the PV grid-connected system model,the current closed-loop control strategy is adopted,and the output current of the inverter is used as the state variable to obtain the control quantity of the control switch device which is close to the ideal.The simulation model of the five-level inverter grid-connected system was built and the simulation results were analyzed and summarized.The final result proves that ISFLA has certain improvement in tracking accuracy and speed and the applicability of current closed-loop control strategy in grid-connected systems.