On Line Monitoring And Evaluation System Of Power Grid Voltage Distortion

With the development of the electrification process,the input of high-power nonlinear loads in the power grid injects a large number of harmonic waves into the power grid,which causes serious voltage distortion and affecting the power quality.However,the existing devices that monitor the power grid operating environment generally have many defects,such as slow data updates in real time,single function,low level of intelligence and so on.The increase of the harmonic content also causes the increase of the energy metering error.This results in a positive error for linear users and a positive error for nonlinear users.It is imminent to monitor and manage high-power nonlinear loads in the access network.Firstly,this article analyzes the causes of harmonic generation in the power grid and summarizes the types of harmonic sources in the power grid.Studies working mechanism and electric energy metering algorithm of the inductive meter and the electronic meter were studied,and the error levels of the electronic and inductive meter in different harmonics were analyzed and calculated.From the principle,the reason for the error was analyzed.Based on this,an energy measurement algorithm based on Fourier analysis is proposed.Through the Fourier decomposition of the voltage and current of the power network before and after the load operation,when it is determined as a non-linear load,the voltage and current are Fourier-decomposed and the energy of each harmonic is calculated,and the harmonics are directly incorporated into the measurement algorithm,which to adapt to the measurement of non-linear loads.At the same time,the flow direction of the harmonic power current is determined,and finally the power consumption of the load is determined.Secondly,using MATLAB to build a non-linear load of power electronic switch type and an electronic energy meter model of energy metering algorithm based on Fourier analysis to simulate the power grid environment under various load operation modes,and to pass the voltage and current under different operating modes.Compared with the power data sheet,the influence of non-linear load on the measurement of the electronic energy meter is verified,and the correctness of the energy metering algorithm based on Fourier analysis is proved.Finally,the hardware platform of the evaluation system is designed and constructed.The hardware platform is divided into four parts: energy acquisition,monitoring and energy metering,remote and short-range communication,and data storage.The software programming implements voltage distortion monitoring and energy metering error evaluation.Through three sets of experiments,the accuracy of hardware platform harmonic monitoring and Fourier-based energy metering algorithms was verified.Finally,the paper gives the error report of the harmonic content and power measurement of the user’s electric environment,and achieves the purpose of the evaluation.This paper proposes a system for monitoring the voltage of power grid and evaluating the accuracy of power measurement for nonlinear load.By improving the metering algorithm and improving the auxiliary functions of the equipment,a reasonable measurement algorithm is used while monitoring the non-linear loads.It ensures the fairness of the power trading market and also provides power companies with large data on non-linear load conditions,providing an effective basis for improving the power grid environment in the future.