A Method for Filtering Low Frequency Disturbance in PMU Data Before Coordinated Usage in SCADA

The PMU data is increasingly used in the grid monitoring system SCADA. As the DFT algorithm used in PMUs fails to distinguish the fundamental frequency signal with low-frequency interference, the low-frequency disturbance (LFD) included in fundamental frequency variable data, which are collected from PMUs, will affect the correctness of calculation and analysis of the power system's steady state. In order to extract the fundamental frequency variable from PMU data, taking low-frequency forced oscillation as an example, a method for filtering LFD in PMU data is proposed. First, the effect of low-frequency oscillation to the fundamental frequency variable is analyzed in this paper. Then, the component of LFD in PMU data is explained. By finding the maximum value and minimum value of voltage or current in PMU data to draw the envelopes and add them together, the mean value or fundamental frequency variable of voltage and current is obtained. The mechanism of error in calculating active power is analyzed when low-frequency oscillation occurs in the power grid. The results of analyzing actual PMU data under low-frequency oscillation verify the correctness of the method proposed in this paper. This method is of great significance to improve the accuracy of calculation in SCADA.