Research On MPPT Control Of Isolated Quasi-Z Source Photovoltaic Inverter

With the use of traditional fossil energy,environmental pollution has intensified,resources have been depleted,and the revolution is inevitably sweeping the globe.Solar energy is one of the fastest growing areas of renewable energy.The development and utilization of solar energy has become the economic development strategy of all countries in the world.Due to the multi-peak characteristics,the traditional MPPT(Maximum Gower Point Tracking)algorithm fails to track the true maximum power point,causing the system to suffer severe power loss.Therefore,the research of maximum power tracking technology under local shadow conditions is the core problem to improve solar energy utilization.The conventional inverter has the disadvantages of a single buck-boost function,poor flexibility,poor reliability,and poor anti-electromagnetic interference capability.In order to overcome the shortcomings of the traditional inverter,this paper adopts the isolated quasi-Z source photovoltaic grid-connected inverter.In this paper,the isolated quasi-Z source inverter is taken as the research object.The maximum power tracking technology,topology,control strategy,simulation model and hardware design under local shadow are deeply studied.The specific contents are as follows:This paper firstly analyzes the necessity and significance of photovoltaic power generation and maximum power tracking technology research,introduces isolated quasi-Z source inverter and maximum power tracking technology under partial shadow.The research status of the converter and MPPT algorithm is briefly discussed.Then the three mathematical models of photovoltaic cells are analyzed and established.On this basis,the mathematical model of the photovoltaic array is established,and the output characteristics of the array under different local shadows are analyzed.Next,the single-peak MPPT algorithm of perturbation observation method(P&O),conductance increment method(INC),self-tuning fuzzy control method(FLC)and particle swarm optimization fuzzy control method under uniform illumination conditions is analyzed.The working principle and the simulation model were established.Finally,the advantages and disadvantages of various methods were discussed through the simulation results.In the following,this paper analyzes the limitations and shortcomings of traditional particle swarm optimization algorithms.Aiming at this shortcoming,a composite MPPT algorithm with improved particle swarm optimization(DPSO)and variable step size perturbation is proposed.This algorithm is suitable for global search under local shadow conditions.excellent.In the first stage of the algorithm,an improved dormant particle swarm optimization algorithm(DPSO)is proposed for the defects and deficiencies of the traditional particle swarm optimization algorithm.The algorithm structure,weighting factor w,maximum search speed Vmax,number of particles Np,particle search order and environment restart conditions are designed.And after improvement,the system quickly finds the approximate location of the maximum power point(GMPP).In the second stage,the improved Fibonacci sequence is used as the basis for the step size change of the variable step disturbance observation method,which accurately and quickly tracks the maximum power point and maintains a stable output to the left of the maximum power.Then analyze the working principle of the isolated quasi-Z source,and establish a small signal model and transfer function.The parameters of the PI and quasi-PR controllers are analyzed and designed by using the double closed loop control strategy of the DC link voltage of the secondary capacitor voltage to indirectly control and the grid-connected current.This simulation uses the SABER/MATLAB co-simulation environment.By comparing the traditional PSO algorithm,the perturbation observation method(P&O)and the composite MPPT algorithm,the system simulation verifies the maximum power tracking in the static local shadow environment and the dynamic local shadow environment.Finally,on the basis of the above work,a 300 W maximum power tracking experimental device is designed,the parameters of the main circuit are designed and selected,the control circuit is designed,and the DSP software system is designed.The experimental results prove the correctness and superiority of the composite MPPT algorithm.