Research On The Key Technology Of Synchronized Phasor Measurement Unit For Power System

Grid, as the most complicated power system, has been slowly evolved in the past half-century. In order to improve the system’s reliability and efficiency and achieve the steady operation, WAMS constructed by PMU, has opened up a new direction for the steady operation and real-time monitoring of the power system. With GPS providing unified time, bus voltage and line current of each node are sampled by PMU synchronously in the power system, and timestamp is provided for each state value. It monitors the state of each monitoring point in the grid, and ensures the grid steady and reliable operation.At first, it introduces the basic principle and research situation at home and abroad of both wide-area measurement system and phasor measurement unit. At the same time, it also analyzes and points out the weaknesses of the current PMU. According to the proposed problems, it mainly makes research on the following several aspects:1. In view of the insufficiency of traditional discrete Fourier transform based phase angle measurement algorithm in both accuracy and real-time performance, the phase angle error of DFT algorithm under the condition of asynchronous sampling is analyzed. Then the functional relationship among phase error, frequency deviation rate and initial sampling phase angle is derived, and an improved phase measurement algorithm based on lean-π/4-rectangular coordinate is proposed. Also the proposed algorithm, which has been verified in MATLAB, has a good merit of correcting the dynamic phase angle error, improving the accuracy of phase angle measurement.2. Considering the inability to provide synchronous clock in the GPS failure condition, it adopts the digital phase-locked loop, and develop a backup clock for PMU using the electronic design automation technology. When GPS works normally, the backup clock will track the pulses per second. Otherwise, the backup clock will switch to an alternative mode and supply a synchronous signal with error in limited range.3. For some PMUs, which can’t be described with original information model in detail, through analyzing the original model and standard of IEC 61850-90-5, an improved model is put forward, explaining the function of communicated service’s structure in each module at detail. Furthermore, it improves the interoperability of PMU,and is of great significance for engineering application reference.At last, software and hardware design of PMU is detailedly introduced based on TMS320F28335 processor. In this part, the modules with the functions of sampling, filtering and amplitude limiting of the signal are explained. Also, the design of AD/DA transfer module, synchronous clock module, data processing modules and vector operation modules are presented elaborately.