Research On Power Quality Of Photovoltaic Power Distribution Network

In recent years,the domestic and foreign photovoltaic power generation technology industry has made important technological progress,and its development and utilization technology has also been widely developed.It has extended the practical application of photovoltaic comprehensive power generation to various current power generation projects,and has continued to expand domestic and foreign markets,the sustainable,healthy and stable development of the photovoltaic power generation industry is maintained.As a new type of renewable energy utilization,distributed photovoltaic integrated power generation mode can be divided into two development modes: off-grid photovoltaic integrated power generation and grid-connected photovoltaic integrated power generation.Among them,the grid-connected photovoltaic power generation system is fully connected to the photovoltaic distribution network through the photovoltaic dedicated line or the public line,it changes the traditional photovoltaic distribution network operation management mode and the industry trend development flow,and improves the quality of power transmission,relay protection,safe power supply automatic devices and daily maintenance of power generation equipment and prevention of power outages,will bring many new problems in power generation technology and operation and maintenance management.From the analysis of the current development trend,the photovoltaic grid-connected technology is relatively mature,but for photovoltaic grid construction companies,the connection of photovoltaic power to the traditional distribution network management is still in a new stage of continuous exploration.Distributed photovoltaic grid-connected power Access to the grid connection method,access to the power supply capacity,access to the power supply location,access to the voltage control level,protection equipment configuration,automatic device protection configuration and power supply monitoring system control technology are not yet mature,and a large number of centralized photovoltaic access will make the grid appear problems such as voltage fluctuations,harmonic pollution,island effect,etc.,which lead to reduced reliability of power supply,difficulty in power flow regulation and control,and low energy utilization,seriously affect the safe and stable operation of the power grid.Therefore,the connection of photovoltaic power to the distribution network has very important practical significance for the research of power quality control.This paper mainly discusses the theory of photovoltaic power supply access to voltage stability analysis of distribution network,harmonic suppression of photovoltaic power distribution network and island effect on distribution strategy of photovoltaic power distribution network,the main research contents are as follows:(1)Analysis of the voltage stability of the distribution network when the photovoltaic power is connected.There are a large number of electronic components and non-linear loads connected to the photovoltaic grid,resulting in grid voltage fluctuations,flickers,and voltage deviations in the power system,at the same time,the photovoltaic power generation system itself has the characteristics of randomness,intermittency,and volatility,so the power quality of the power system cannot meet the national requirements.The mathematical model of the working principle of building photovoltaic cells,the grid-connected photovoltaic system inverter circuit model and the distribution network feeder system model,analyze the factors that cause voltage fluctuations,and research the influence of different PV output and access locations on the distribution network voltage,and calculate a single When PV access,multiple PV access locations and access capacities are different,the distribution voltage of the distribution network line is simulated,the process of system voltage change caused by the power factor change of the photovoltaic power supply is simulated and analyzed,and the best location and location of the photovoltaic power supply access are selected.Optimal capacity,effectively solve the problem of PV access node voltage limit.(2)Harmonic suppression of photovoltaic power distribution network.The structure of the distribution network is complex,the access capacity and location diversity of the photovoltaic power supply affect the harmonic analysis of the distribution network,the nonlinear device characteristics of the harmonics cause a large number of high-frequency harmonics when working on the power grid,the capacitor may be damaged and cannot beused normally.This paper analyzes the influence of harmonics on the distribution network,researches the impact of different output power of photovoltaic power on current harmonics,considers the harmonic distribution characteristics of grid-connected photovoltaic power generation systems in island mode,discusses the occurrence of breakdown faults,and analyzes the shortcomings and problems of the traditional harmonic suppression methods in the island mode are presented,and the harmonic current suppression strategy of the grid-connected photovoltaic power generation system in the island mode is proposed.(3)Research on the impact strategy of island operation on photovoltaic power distribution network.Combined with the relevant technical standards of photovoltaic power plants and photovoltaic transmission and distribution networks,a unified integrated circuit design model for grid-connected photovoltaic power generation systems has been established,however,when photovoltaic power is connected to the distribution network,it will increase the complexity of the power system and change the grid harmonics.Power flow distribution exposes the system to the risk of voltage overruns.Aiming at the non-convergence of the forward pushback method to deal with the power flow of the radiation network,an improved power flow algorithm combined with the loop analysis method and the forward pushback method is proposed.By decomposing the branch current,the current at the split point of the radiation network is compensated to change the non-convergence phenomenon,and the effectiveness and accuracy of this algorithm are verified by MATLAB simulation.At the same time,the generation and influence of island effect are analyzed,and the Matlab/Simulink island operation monitoring simulation analysis model is established,through studying the island effect monitoring method,the island can be accurately monitored by the active detection method when the distribution network is disconnected from the photovoltaic power supply,the generation of effects,thereby reducing the occurrence of island effects.