Research And Implementation Of Synchronized Phasor Measurement Algorithms

With the development of GPS-based communication technology, the technique of synchronized phasor measurement in power system, which is very important to system state estimation, stability control, fault identification and relay protection, is arousing increasingly great concern.Firstly, the function and theory of synchronized phasor measurement is introduced. With the sum-up of existing algorithms of synchronized phasor measurement, the advantages and disadvantages of the algorithms are indicated.Consequently, based on the comprehensive analysis of spectral leakage that is caused by asynchronous sampling and non-integral period truncation in the harmonic analysis of power system with fast Fourier transform, a formula is deduced between the leakage spectrum and actual spectrum. An improved algorithm, which uses phase difference to correct signal frequency and then recoveries actual spectrum, is presented. The algorithm can calculate more accurately with short sample duration, and the speed of response is faster. Compared with widely used window and interpolation algorithm which has to prolong the sample duration to improve the calculating accuracy, real time of the algorithm is better. But the calculating burden with the improved method is a little heavy, which limits the range of application. Based on the intensive analysis of DFT error, and shortcomings of the previous correcting methods, an improved algorithm that employs the average value to modify the ratio of deviation of signal frequency is proposed. And the calculating burden with the improved algorithm is slighter heavier. Simulation results show that the proposed method can calculate more accurately than the previous method even though the signal frequency deviation is up to±5 Hz. And the result of Total Vector Error (TVE) is less than 0.4%. The favorite performance satisfies the demand of accuracy and real-time of synchronized phasor measurement very well.Finally, employing the second improved phasor algorithm, a project of designing PMU based on technologies of DSP and CPCI is presented. The project is easy to implement, which takes full advantages of the ability in data processing of DSP and high speed, high reliability and hot swap capable computer bus of CPCI. And the system has a high performance. Besides, the implementation process of software and hardware is given. The testing experiment demonstrates the project is feasibility.