Research On Phasor Measurement Algorithm And Its Monitoring Software System

The interconnection of regional power grids improves the economic performance of power system operation,and the reform of electric power industry improves the efficiency of electric power production.These measures bring huge benefits,but also make the operation environment of the power grid become more and more complex.With the development of nonlinear load and micro distributed generation in the future,as well as the increase of new energy demand,the demand for power network monitoring and protection technology will be higher and higher.Synchronous phasor measurement technology is the core technology of wide area measurement system.The precision of synchronous phasor measurement algorithm will directly affect the application effect of wide area measurement system.This thesis presents an improved Taylor weighted least squares algorithm suitable for dynamic state of power grid and an improved discrete Fourier transform algorithm suitable for real-time measurement.A phasor measurement and monitoring software system based on We Chat public platform is developed.The main work of this thesis is divided into the following points:(1)On the basis of consulting a large number of domestic and foreign literature,the research background of this subject is further studied and analyzed.The research status of phasor measurement units standard,synchronized phasor measurement technology and algorithm at home and abroad is analyzed and summarized.(2)Most phasor measurement algorithms consider signal phasors as a steady-state model,so they are very sensitive to voltage amplitude and angle fluctuations that often occur in modern power grids.Taylor weighted least squares algorithm relies on a dynamic phasor model at nominal frequency.The algorithm not only provides the phasor values but also provides its derivatives to improve the dynamic monitoring of the power grid.On this basis,an improved Taylor weighted least squares method based on fundamental frequency is proposed.First,the fundamental frequency is obtained by nonlinear least squares method.Then,the derivation process of the Taylor weighted least squares algorithm based on the calculated fundamental frequency is introduced,and the window function,the length of the data window and Taylor polynomial order involved in the algorithm are analyzed and selected.Finally,the performance of the algorithm is verified by different signal models and actual data.(3)In order to achieve real-time monitoring and weakening the influence of spectrum leakage,a real-time frequency and amplitude measurement algorithm based on improved discrete Fourier transform is proposed.Firstly,the discrete Fourier transform algorithm considering frequency offset is deduced theoretically.Then,in order to reduce the effect of spectrum leakage,the results of discrete Fourier transform are recalculated.The expressions of frequency and amplitude are given.In order to further improve the accuracy,the frequency value is estimated two times.Finally,the performance of the algorithm is verified by different signal models and actual data.(4)According to the system function design,the phasor monitoring software system based on the WeChat public platform is completed.The system uses Servlet technology to realize between the We Chat server and the local server connection and data exchange,and uses API(Application Programming Interface)technology to create a custom menu,and uses JSP(Java Server Pages)technology to realize all page editing,and uses JDBC(Java Data Base Connectivity)technology to realize data query,and uses ECharts drawing technology to realize the curve drawing.The user can obtain real-time information of voltage and frequency by the form of scanning code,and can also view the historical information of voltage and frequency in form or graphic form.