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Journal ArticleDOI

A Nonlinear Adaptive Filter for Online Signal Analysis in Power Systems: Applications

07 Aug 2002-IEEE Power & Energy Magazine (IEEE)-Vol. 22, Iss: 1, pp 72-72
TL;DR: In this paper, a nonlinear adaptive notch filter based on the concept of an enhanced phase-locked loop (PLL) is proposed for online signal analysis for power systems protection, control and power quality enhancement.
Abstract: This paper presents various applications of a nonlinear adaptive notch filter which operates based on the concept of an enhanced phase-locked loop (PLL). Applications of the filter for online signal analysis for power systems protection, control and power quality enhancement are presented. The proposed scheme can be applied for signal analysis both under stationary and nonstationary conditions. Based on digital time-domain simulations, applications of the filter for (a) sinusoidal waveform peak detection, (b) harmonic identification/detection, (c) detection/extraction of individual components of a signal, (d) instantaneous reactive current extraction, (e) disturbance detection, (f) noise reduction in zero-crossings detection, and (g) amplitude (phase) demodulation for flicker estimation, are presented.
Citations
More filters
Journal ArticleDOI
TL;DR: In this paper, a self-synchronized synchronverter is proposed to improve the performance of grid-connected inverters by removing the dedicated synchronization unit, which can automatically synchronize itself with the grid before connection and track the grid frequency after connection.
Abstract: A synchronverter is an inverter that mimics synchronous generators, which offers a mechanism for power systems to control grid-connected renewable energy and facilitates smart grid integration. Similar to other grid-connected inverters, it needs a dedicated synchronization unit, e.g., a phase-locked loop (PLL), to provide the phase, frequency, and amplitude of the grid voltage as references. In this paper, a radical step is taken to improve the synchronverter as a self-synchronized synchronverter by removing the dedicated synchronization unit. It can automatically synchronize itself with the grid before connection and track the grid frequency after connection. This considerably improves the performance, reduces the complexity, and computational burden of the controller. All the functions of the original synchronverter, such as frequency and voltage regulation, real power, and reactive power control, are maintained. Both simulation and experimental results are presented to validate the control strategy. Experimental results have shown that the proposed control strategy can improve the performance of frequency tracking by more than 65%, the performance of real power control by 83%, and the performance of reactive power control by about 70%.

793 citations

Journal ArticleDOI
TL;DR: In this article, an enhanced phase-locked loop (EPLL) based synchronization method is proposed for distributed generation units, e.g., wind generation systems, which utilize power electronic converters as an integral part of their systems.
Abstract: This paper presents a new synchronization method which employs an enhanced phase-locked loop (EPLL) system. The operational concept of the EPLL is novel and based on a nonlinear dynamical system. As compared with the existing synchronization methods, the introduced EPLL-based synchronization method provides higher degree of immunity and insensitivity to noise, harmonics and other types of pollutions that exist in the signal used as the basis of synchronization. The salient feature of the EPLL-based synchronization method over conventional synchronization methods is its frequency adaptivity which permits satisfactory operation when the centre frequency of the base signal varies. The proposed EPLL-based method of synchronization is also capable of coping with the unbalanced system scenarios. Structural simplicity of the EPLL-based method greatly simplifies its implementation in digital software and/or hardware environments as an integral part of a digital control platform for power electronic converters. The primary application of the proposed synchronization method is for the distributed generation units, e.g., wind generation systems, which utilize power electronic converters as an integral part of their systems.

565 citations


Cites methods from "A Nonlinear Adaptive Filter for Onl..."

  • ...An implementation of EPLL of [9] is shown in Fig....

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  • ...This section is devoted to the EPLL of [9] which is used as the building block of the proposed synchronization scheme of this paper....

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  • ...The main building block of the synchronization method is an enhanced phase-locked loop (EPLL) system which operates as a nonlinear dynamical system [9]....

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Journal ArticleDOI
TL;DR: A phase-locked loop (PLL) is a nonlinear negative feedback control system that synchronizes its output in frequency as well as in phase with its input PLLs are now widely used for the synchronization of power-electronics-based converters and also for monitoring and control purposes in different engineering fields as mentioned in this paper.
Abstract: A phase-locked loop (PLL) is a nonlinear negative-feedback control system that synchronizes its output in frequency as well as in phase with its input PLLs are now widely used for the synchronization of power-electronics-based converters and also for monitoring and control purposes in different engineering fields In recent years, there have been many attempts to design more advanced PLLs for three-phase applications The aim of this paper is to provide overviews of these attempts, which can be very useful for engineers and academic researchers

563 citations

Journal ArticleDOI
TL;DR: A multiple-complex coefficient-filter-based PLL is presented, and its unique feature lies in the accurate and rapid extraction of the positive and negative sequence components from the polluted grid voltage, and the harmonic components can also be estimated precisely.
Abstract: Synchronization with the utility networks is crucial for operating three-phase grid-interfaced converters. A challenge of synchronization is how to fast and precisely extract the fundamental positive and negative sequences under the distorted and unbalanced conditions. Many phase-locked loop (PLL) and synchronization techniques have been presented in the past decades. Most of them make a tradeoff between the accuracy and dynamic response under severe distorted and unbalanced conditions. In this paper, a multiple-complex coefficient-filter-based PLL is presented, and its unique feature lies in the accurate and rapid extraction of the positive and negative sequence components from the polluted grid voltage, and the harmonic components can also be estimated precisely, which has the potential use for selective compensation in active filter applications. Another advantage of the proposed method is its flexibility for simplifying its structure in some specified conditions. Results of continuous-domain simulations in MATLAB and discrete-domain experiments based on a 32-b fixed-point TMS320F2812 DSP are in good agreement, which confirm the effectiveness of the proposed method.

402 citations


Cites background from "A Nonlinear Adaptive Filter for Onl..."

  • ...From Table I, it can be observed that DSOGI and EPLL have a longer response time....

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  • ...Similar to EPLL, a powerful nonlinear approach was presented by Yazdani et al. [19], which is based on an adaptive notch filter (ANF) and has a fast dynamic response compared to EPLL [20]....

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  • ...On the other hand, Ghartemani and Iravani presented an enhanced PLL (EPLL) [17], whose core is an adaptive filter....

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Journal ArticleDOI
TL;DR: In this paper, the dc component in the input signal of the phase-locked loop (PLL) and notch filter algorithms applied to filtering and synchronization applications is addressed, based on adding a new loop inside the PLL structure.
Abstract: This paper presents a method for addressing the dc component in the input signal of the phase-locked loop (PLL) and notch filter algorithms applied to filtering and synchronization applications. The dc component may be intrinsically present in the input signal or may be generated due to temporary system faults or due to the structure and limitations of the measurement/conversion processes. Such a component creates low-frequency oscillations in the loop that cannot be removed using filters because such filters will significantly degrade the dynamic response of the system. The proposed method is based on adding a new loop inside the PLL structure. It is structurally simple and, unlike an existing method discussed in this paper, does not compromise the high-frequency filtering level of the concerned algorithm. The method is formulated for three-phase and single-phase systems, its design aspects are discussed, and simulations/experimental results are presented.

338 citations


Additional excerpts

  • ...7, where μ1 , μ2 , and μ3 are positive real numbers [24], [25]....

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References
More filters
Journal ArticleDOI
TL;DR: In this paper, a unified power quality conditioner (UPQC) is proposed to compensate for voltage flicker/imbalance, reactive power, negative-sequence current and harmonics.
Abstract: This paper deals with unified power quality conditioners (UPQCs), which aim at the integration of series-active and shunt-active power filters. The main purpose of a UPQC is to compensate for voltage flicker/imbalance, reactive power, negative-sequence current and harmonics. In other words, the UPQC has the capability of improving power quality at the point of installation on power distribution systems or industrial power systems. This paper discusses the control strategy of the UPQC, with a focus on the how of instantaneous active and reactive powers inside the UPQC. Experimental results obtained from a laboratory model of 20 kVA, along with a theoretical analysis, are shown to verify the viability and effectiveness of the UPQC.

1,042 citations


"A Nonlinear Adaptive Filter for Onl..." refers methods in this paper

  • ...Various approaches, e.g., notch filtering, Fourier analysis, and instantaneous reactive power theory, have been proposed to generate a reference signal for an active filter [4]‐[ 7 ]....

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Journal ArticleDOI
TL;DR: In this article, the use of wavelet transforms for analyzing power system fault transients in order to determine the fault location is described, which is related to the travel time of the signals which are already decomposed into their modal components.
Abstract: This paper describes the use of wavelet transforms for analyzing power system fault transients in order to determine the fault location. Traveling wave theory is utilized in capturing the travel time of the transients along the monitored lines between the fault point and the relay. Time resolution for the high frequency components of the fault transients, is provided by the wavelet transform. This information is related to the travel time of the signals which are already decomposed into their modal components. The aerial mode is used for all fault types, whereas the ground mode is used to resolve problems associated with certain special cases. The wavelet transform is found to be an excellent discriminant for identifying the traveling wave reflections from the fault, irrespective of the fault type and impedance. EMTP simulations are used to test and validate the proposed fault location approach for typical power system faults.

606 citations

Journal ArticleDOI
TL;DR: In this article, the instantaneous active-reactive power and current on /spl alpha/-/spl beta/ orthogonal coordinates have been defined by the so-called p-q theory.
Abstract: This paper proposes a new definition of the instantaneous active-reactive current and power based directly on instantaneous space vectors on polar coordinates, and presents its application. The definition is applicable in three-phase three-wire systems. The instantaneous active-reactive power and current on /spl alpha/-/spl beta/ orthogonal coordinates have been defined by the so-called p-q theory. In comparison with the p-q theory, our new definition offers a lucid physical concept for the active-reactive current and power in three-phase circuits. The new method, thus, can decompose current into the instantaneous active and reactive currents without calculating the instantaneous active and reactive powers. An application example is presented to confirm the validity and practicability of the new definition using digital simulation.

174 citations


Additional excerpts

  • ...-to- transformation technique is a widely accepted approach for high performance compensators [5], [ 6 ]....

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Journal ArticleDOI
TL;DR: A systematic design procedure is described for the proposed filter-based synchronization method, taking into account the specified line frequency tolerance.
Abstract: A simple combination of nonlinear and linear digital signal processing methods is proposed for efficient noise reduction in zero crossing detectors. The method is very robust against strong impulsive noise, typically encountered in thyristor power converters, where reliable zero crossing detection is required for firing synchronization. A systematic design procedure is described for the proposed filter-based synchronization method, taking into account the specified line frequency tolerance. The fully digital signal processing approach allows compact implementations, and supports flexible interfacing to digital motor control systems. >

168 citations


"A Nonlinear Adaptive Filter for Onl..." refers background in this paper

  • ...[ 13 ]. In practice, the 50/60 Hz sinusoid is seldom distortionless, and high level noise that typically consists of deep and wide notches, can easily lead to erroneous zero-crossing detections [13]....

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  • ...[13]. In practice, the 50/60 Hz sinusoid is seldom distortionless, and high level noise that typically consists of deep and wide notches, can easily lead to erroneous zero-crossing detections [ 13 ]....

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Journal ArticleDOI
TL;DR: In this paper, an approach that accounts for the time-varying nature of the fundamental and harmonic components is developed to detect high-impedance faults accompanied by variations in the 60 Hz and harmonic component.
Abstract: High-impedance faults are accompanied by variations in the 60 Hz and harmonic components. An approach that accounts for the time-varying nature of the fundamental and harmonic components is developed. This approach is based on Kalman-filtering theory to obtain the best estimation of the time variations of the fundamental and harmonic components. Four actual recorded data sets for staged arcing fault on different types of soil are investigated by the proposed Kalman-filtering technique. The time variations of fundamental and low-order harmonic components significantly contribute to high-impedance fault detection using the features presented. >

164 citations


"A Nonlinear Adaptive Filter for Onl..." refers methods in this paper

  • ...Various disturbance detection methods have been proposed/implemented [8]‐[ 12 ]....

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