Research On Phasor Measurement Algorithm And Its System Software

Along with the acceleration of the interconnection of the power network and the expansion of the system, the structure of power grid is becoming more and more complex, so real-time monitoring and controlling of the power grid was particularly important in electric power system operation. Frequency, phase angle and amplitude are three basic elements of the power system, they also reflect the basic operating characteristics of the grid. Wide area measurement system based on phasor measurement units can monitor the operational status of the power system, ensuring that the power system in good working condition.The domestic and foreign research present situation of the phasor measurement unit have been briefly described in this thesis, then it summarizes and analyses the applications of phasor measurement technology in power system. The phasor measurement algorithm is the core issue of phasor measurement device, and discrete Fourier Transform (DFT) algorithm is the basic algorithm to calculate the phasor, it is also a successful algorithm. Under the synchronous sampling condition, the phasor measurement unit can accurately capture the time stamped phasor information when sampling the original electrical signal. But when the grid-frequency offset, that is, non-synchronous sampling, The error of phasor measurements have been existed due to the hurdle effect and spectrum leakage of DFT.There are two types of expression in phasor representation:rotating phasor and stationary phasor, they are differented form the expression. By analyzing the source of the error on the DFT algorithm, the improved DFT algorithm have been adopted, firstly adding window to sampling data, and then taking into account the frequency shifting factor and computation burden, the precise phasor value can be obtained by DFT phasor correction factor and recursive algorithm. By Comparing this algorithm with two-state Kalman filter algorithm, this algorithm should be better than the two-state Kalman algorithm and its accuracy is within the specification requirements when its amplitude is stable and frequency shift or change slowly under conditions of power system stability, Meanwhile, the correction coefficient of the algorithm have been used to monitor operating state of the power network.According to work principle of phasor measurement unit, the phasor measurement monitoring and management software based on client/server mode and VS2005 platform have been designed. It is necessary to make a choice that which database to use and how to access the database before designing this software, database operations and data acquisition on host computer have been achieved by ADO technology and Socket network programming technology respectively, data analysis have become realized through C Sharp and Matlab hybrid programming, namely solving phasor parameters by matlab function, the implementation of data management and real-time monitoring have been solved by SQL 2005 database and thread. The data image display have been achieved by Zedgraph control, thus it realizes data acquisition, data analysis, data management, and data real-time monitoring function in the upper machine.The regional management is very important to the grid, and it’s facilitated by the achievement of information publishing and management system based on web technology. It provides a method of monitoring on local area network site, index calculating and analyzing of the historical data, displaying of the real-time grid frequency. IIS have been used for server management software of the system. The information of sub station and historical data have been obtained from Web data server by ADO.NET technology, the display of historical data analysis have been shown by Zedgraph Web control, the real-time data have been obtained by Socket network programming technology and the real-time display of grid frequency have been achieved by Ajax technology.This paper have provided a theoretical research on phasor measurement algorithm and system software, and further application have been made in the research combined with practice, it has a certain practical significance influence on the development of wide area measurement system.