Decaying DC Offset Current Mitigation in Phasor Estimation Applications: A Review

Abstract

Decaying DC (DDC) offset current mitigation is a vital challenge in phasor current estimation since it causes malfunctioning/maloperation of measurements and protection systems. Due to the inductive nature of electric power systems, the current during fault inception cannot change immediately and it contains a transient oscillation. The oscillatory component acts similar to an exponential DC signal and its characteristics depend on the X/R ratio of the system, fault location, and fault impedance. DDC attenuates accurate phasor estimation, which is pivotal in protection systems. Therefore, the DDC must be eliminated from the fault current (FC) signal. This paper presents an overview of DDC mitigation methods by considering different groups—before the discrete Fourier transform (pre-DFT), after the discrete Fourier transform (post-DFT), the least square-based (LS-based), and other methods. Through a comprehensive review of the existing schemes, the effects of noise, harmonics, multiple DDCs (MDDCs), and off-nominal frequency (ONF) on the accuracy of DDC estimation, were recognized. A detailed discussion (along with some simulation results) are presented to address the main advantages/disadvantages of the past studies. Finally, this paper presents a few suggestions for future researchers, for researchers to investigate more implementable solutions in this field.

Analysis of Factors Affecting Electric Power Quality: PLS-SEM and Deep Learning Neural Network Analysis

“…Table .1 Voltage harmonic distortion (Source: Circular 39 of the Ministry of Industry and Trade issued on November 18, 2015, Vietnam, regulating the distribution power system) Design measures to reduce harmonic loss and provide suitable operating solutions for users to improve the operating efficiency of electrical equipment such as: replacing damaged equipment, using AC reactors or coils resistance, DC for inverter, 12-pulse rectifier solution, using an inverter with low harmonics, using filter [31], [32].…”

“…Industrial 4.0 is increasingly developing, automatic switching control systems are mostly used in electrical equipment, lighting loads such as LEDs are widely used, and the above devices are the main cause of harmonic generation. Furthermore, these benefits encourage preventive action in terms of reduced energy quality values, increased temperatures, and reduced power factor [10], [11], [12]. The main sources of harmonic generation tend to cost clients significantly.…”

A Novel Method for Removal of Dual Decaying DC Offsets to Enhance Discrete Fourier Transform-Based Phasor Estimation

“…However, the fault current signal is contaminated by decaying DC offsets (DDCOs), thereby compromising the accuracy and convergence speed of the DFT [1,2]. Various methods have been used to remove DDCOs from fault current signals [3]. Assuming that DDCO exhibited a specific time constant, DDCO was completely removed by a Kalman filter in [4,5] and a digital mimic filter in [6].…”