A PLL-Based Multirate Structure for Time-Varying Power Systems Harmonic/Interharmonic Estimation

Abstract

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On phasor estimation for voltage sags detection in a smart grid context

“…nominal [9]; lasting from few milliseconds to few cycles. Voltage sags are caused by abrupt increases in loads such as phase-to-phase or phase to ground short circuits, they are also caused by abrupt increases in source impedance during a loose of connection [21].…”

“…Also the RMS value is used to estimate the amplitude of the phasor, but RMS is based upon averaging of sampled data during one cycle, so it cannot represent instantaneous information. As voltage sags lead to transient phenomena (voltage unbalance and voltage/current waveform disturbances) [21], it is obvious that the Fast Fourier Transform (FFT) and other techniques based upon it, are no longer valid if they have been used in some cases [6]. Advanced signal processing techniques are therefore required to deal with the complexity and uncertainty associated with a smart grid.…”

“…Using (21), the instantaneous amplitude and instantaneous phase in discrete formulation are given by:…”

A survey of techniques applied to non-stationary waveforms in electrical power systems

“…The results presented show an improvement in the transient response time if compared to the proposed in [60], but convergence time is still a problem, although the related computational effort is reduced. In [62], a new version of the proposed method presented in [61] is shown. Such a new version is concerned with the concept of apparent frequency and undersampling and its application shows an accuracy quite similar to earlier version and an improvement in both transient response time and computational burden, although the transient issue is still present.…”

Slow sampling on-line harmonics/interharmonics estimation technique for smart meters

“…With the increased use of nonlinear loads, battery chargers, electronic ballasts, single-phase power supplies, motor drives, saturable devices, active power filters (APFs), and flexible ac transmission system (FACTS) devices in modern power systems, harmonic distortions in line voltage and current have become more serious than ever before [1][2][3][4]. Harmonic pollution causes power quality (PQ) decline, extra losses in transmission lines and cables, overheating of electrical machines, and malfunction of relays and breakers in power systems [2].…”