Tracking of time-varying grid voltage using DFT based second order generalized integrator technique

This paper proposes a robust, fast and accurate estimation technique for the tracking of time-varying grid voltage parameters. The proposed technique consists of a fundamental frequency tracking method based on a fixed window discrete Fourier transform (DFT) and a quadrature signal generator (QSG) based on a second order generalized integrator (SOGI) in order to track the fundamental amplitude and phase angle. The spectral leakage property of the fixed window DFT is used to track the time-varying fundamental frequency which is subsequently used as the resonance frequency of the QSG-SOGI to generate the orthogonal waveforms of the grid voltage fundamental component. The performance of the proposed DFT based SOGI technique is also compared with the frequency locked loop (FLL) based QSG-SOGI (SOGI-FLL), phase-locked loop (PLL) based on the QSG-SOGI (SOGI-PLL) and quadrature PLL (QPLL) techniques. The superior performance of the proposed technique is verified using synthetically generated grid voltage waveforms in MATLAB/Simulink.