A Family of Gradient Descent Grid Frequency Estimators for the SOGI Filter

• Published in: IEEE transactions on power electronics Vol. 33; no. 7; pp. 5796 - 5810
• Main Authors: Matas, Jose, Martin, Helena, de la Hoz, Jordi, Abusorrah, Abdullah, Al-Turki, Yusuf A., Al-Hindawi, Mohammed
• Format: Journal Article Publication
• Language: English
• Published: New York IEEE 01.07.2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptive filters; Algorithms; Band-pass filters; Computer simulation; Enginyeria elèctrica; Estimators; Filtering theory; Frequency estimation; Frequency locked loops; generalized integrators; Generalized integrators (GIs); Gradient descent estimator; Harmonic analysis; Llaços de seguiment de fase; Microprocessors; Neural networks; online grid-frequency estimation; Phase locked loops; Power harmonic filters; power quality; second-order generalized integrator (SOGI) filter; SOGI filter; Voltage distortion; Voltage sags; Àrees temàtiques de la UPC
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2017.2748920

This paper applies the adaptive gradient descent method to the second-order generalized integrator (SOGI) filter in order to find an online estimation algorithm for the grid frequency, which leads to the proposal of three possible estimators. One of them is identical to the frequency-locked loop algorithm reported in the literature, which proves that it should be understood as a gradient descent estimation algorithm and not as a "frequency locked loop." The proposed gradient descent estimators are simple and suitable to be implemented into a digital processor with small computational burden. However, due to the SOGI characteristics, the estimators show to be especially sensitive to subharmonic and dc-offset voltage distortion. These problems are removed adopting a cascaded double SOGI approach, which strongly increases the rejection capability to harmonics and enhances the response to voltage sags. Simulation and experimental results are provided to validate the proposed contribution.