New Procedure for Estimation of Power Fundamental Phasor Parameters in Presence of Decaying DC Components

Abstract

The paper proposes a new algorithm for the estimation of the fundamental phasor in a power system, based on the removal of exponentially decaying DC components (DDCs). These components, as well as high-order harmonics and noise components, have a considerable effect on accuracy and speed of convergence in numerical and digital relays – speed of the protection relay operation. A Discrete Fourier Transform (DFT) based approach with a modified Prony method was used to calculate and remove the unwanted effect of DDCs in a time interval slightly longer than the period of the fundamental harmonics. The proposed procedure offers the possibility to estimate the parameters of unwanted DDCs in a simpler and analytically more precise way, thus facilitating its program implementation. The algorithm offers the ability to easily adjust the response speed - detection time. This flexibility of the algorithm provides a compromise in terms of response speed as well as expected reliability and security of fault detection. The developed procedure enables the monitoring of the very demanding dynamics of the current signal in short-circuit conditions, and thus the estimation of the phasor parameters of the energy signal so that the relay protection can respond to this emergency in the most adequate (adaptive) way - it becomes more precise and faster in its response. The algorithm has low numerical and computational complexity while maintaining its high performance even in conditions of a very strong noise signal. The simulation results for different test signals demonstrate high precision in the estimation of the fundamental phasor of the proposed algorithm.