Study of Measurement Data Abnormal Fluctuation Caused by High-order Harmonics in Power System and Its Measures

With the large-scale application of power electronic devices on the “Source-Net-Load” side, the power grid has been injected a large number of harmonics and inter-harmonics and is becoming electronic power systems. The existing measurement devices cannot meet this challenge. Taking the abnormal fluctuation event of bus voltage measurement value of a UHV power plant along the line as an opportunity, the wide frequency measurement device is used to analysis and solve the problem. The high-order harmonics has been found in the power grid by the device and its distribution is related to the operation mode of the main transformer. Based on this, we located in and clarify the reason, the measurement function of the measuring device is disturbed by high-order harmonic aliasing. The mechanism of measurement data fluctuation caused by the interaction between high-order harmonic aliasing component and fundamental component at a specific sampling frequency is analyzed. Though the simulation with MATLAB, the characteristics of field data are reproduced to verify the analysis conclusion. On this basis, it is pointed out that high-order harmonics in UHV should be monitored and concerned. The technical measures and suggestions are given from the perspectives of device R&D, detection, filtering and wide-frequency measurement monitoring, that can improve the quality of measurement data, timely understand the new characteristics of power grid and ensure the safe and stable operation of power grid.