A nonlinear filtering technique along with RD and TLS-ESPRIT for mode identification of ambient data

The analysis of electromechanical modes has become a major concern in power system. A spectral estimation technique using a nonlinear filter for identifying the inter-area oscillatory modes for ambient data is presented in this paper. The proposed method contains three steps: (1) non-linear filtering to remove the non-linear trends from the ambient signals (2) Random decrement (RD) technique for obtaining the free decay response from the pre-filtered ambient data and (3) TLS-ESPRIT method for estimating the frequency and damping from these impulse responses obtained using RD. The proposed method is compared with RDT-TLS-ESPRIT method using simulated test signals for ambient data. Comparison of the proposed method is further carried out for actual ambient signals received from a PMU connected to Indian grid. The results shows that the proposed method is able to identify the modes accurately, and hence is suitable for application in wide area monitoring of oscillatory modes.