Photovolaic Power System Control And Islanding Detection Technology

At present,the process of social industrialization in our country is accelerating,and energy demand is becoming increasingly urgent.Driven by the national energy revolution policy,the new energy power generation system,as a clean,efficient,and sustainable use of distributed systems,is increasing in number,expanding in scale,and increasing the penetration rate of power grids.The research on new energy power generation system involves grid connection technology,island detection technology,etc.Among them,the island issue is one of the focuses of people's attention.The islanding effect will cause certain harm to power systems,electrical equipment and maintenance personnel.Therefore,research on islanding detection and protection technology is very important.This article takes the photovoltaic grid-connected system as the research object,the main work is as follows:(1)Analyze the characteristics of the photovoltaic system and summarize three important issues that need to be studied in the grid-connected photovoltaic system,namely the MPPT optimization control problem,the grid-connected control problem,and the islanding detection problem.(2)Summarizing the advantages and disadvantages of the common MPPT control methods,an adaptive incremental step-by-step conductivity increment method was designed to improve the dynamic response speed and control accuracy of the PV grid-connected system MPPT control.In-depth study of the control principle of the three-phase grid-connected system,the state equation of the inverter in the stationary three-phase coordinate system is transformed into the state equation in the dq synchronous coordinate system,and the active and reactive power control is implemented using a PI controller to achieve grid connection requirements.(3)A hybrid energy storage scheme using a battery and a super capacitor was studied.The battery adopts a hysteresis current charge and discharge control strategy and adopts a single current loop control.This control strategy suppresses the fluctuation of the filtered power and prolongs the service life of the battery.The super capacitor provides the highfrequency part of the unbalanced power and maintains the DC bus.Voltage stability.In the control section of the ultra-capacitor Buck/Boost bidirectional converter,a load change and input voltage change are introduced to achieve stable,quasi,and fast control of the DC bus voltage.(4)Summing up common islanding detection methods,based on the analysis of constant active current disturbance method and periodic active current disturbance method in active current perturbation method,an adaptive active current disturbance scheme is studied.This scheme overcomes The traditional method has the defects of detecting dead zone and large fluctuation of output power.(5)Build a MATLAB/SIMULINK simulation platform for photovoltaic power generation,and carry out a system-to-grid and island detection simulation of the design scheme,and analyze the experimental results.