Journal Volume 13 Issue 1

Optimal number and location of measurement instruments in distributed systems for Harmonic State Estimation

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Carlo Muscas, Fabrizio Pilo, Giuditta Pisano, Sara Sulis

The recent studies about the attribution of the responsibilities for harmonic distortion in electric distribution systems show that the most promising approaches are based on measurement data acquired simultaneously in different nodes of the network. Therefore, distributed measurement systems are needed. For economic reasons, only a small part of network nodes can be equipped with measurement instruments, whereas the information about the overall status of the electric system has to be evaluated by means of suitable Harmonic State Estimation (HSE) techniques.

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Active Current, Reactive Current, Kirchhoff's Laws and Tellegen’s Theorem

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Jacques L. Willems

The relations between the basic laws of circuit theory (Kirchhoff's laws and the conservation of generalized power) are discussed with respect to the active and reactive current components. It is shown that the active and reactive currents do not satisfy Kirchoff’s current law. It is proved that this is not in contradiction with the property that the active and reactive powers satisfy the conservation property.

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Generalized symmetrical components for periodic non-sinusoidal Three-phase signals

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Paolo Tenti, Jacques L. Willems, Paolo Mattavelli, Elisabetta Tedeschi

This paper deals with the generalization of the symmetrical components technique to periodic non-sinusoidal three-phase currents and voltages. The generalization of the concept of symmetrical components is discussed together with their derivation in both time and frequency domain. The main conclusion of the paper is that an orthogonal decomposition of periodic nonsinusoidal three-phase signals into positive sequence, negative sequence and zero-sequence components is not possible, but that an additional current and voltage component should be introduced, which is called the residual component.

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Compensation Techniques Based on Reactive Power Conservation

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Paolo Tenti, Paolo Mattavelli, Elisabetta Tedeschi

The paper introduces two definitions of instantaneous reactive power terms, which are conservative in every network and apply even under non-sinusoidal conditions. Both quantities coincide with usual reactive power for sinusoidal operation, however they assume a different meaning for distorted behaviour. The first one is an energy-related term, and its unbiased integral accounts for the average energy stored in the network. The second has a differential nature and is suitable for dynamic analysis and control of harmonic and reactive power sources acting in the network.

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Amplitude and Phase Modulation Effects of Waveform Distortion in Power Systems

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Roberto Langella, Alfredo Testa

The amplitude and phase modulation effects of waveform distortion in power systems are analyzed. Recalls on Amplitude Modulation (AM) and Phase Modulation (PM) are given with particular reference to spectral components. Then, simple inverse formulas are obtained to demonstrate that summations of one or more small tones frequencies to a given tone of interest can always be interpreted in terms of AM and PM. The usefulness of AM and PM representation, in particular in the presence of interharmonic tones, is demonstrated with reference to simple case-studies and practical applications.

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Assessment of Fault Location in Power Distribution Networks

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Alberto Borghetti, Mauro Bosetti, Mauro Di Silvestro, Carlo Alberto Nucci, Mario Paolone, Lorenzo Peretto, Elisa Scala, Roberto Tinarelli

Methods aimed at locating the position where a fault is occurred can be seen as part of a complex measurement system oriented at more general power quality purposes. This paper faces the comparison between two methods recently proposed in literature for fault-location in distribution networks, based on a distributed and on a single-ended measurement system, respectively. By assuming a common distribution system topology, the two methods are applied in order to compare their performances as well as the obtained results.

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About the Rejection of Poynting Vector in Power Systems Analysis

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Alexander E. Emanuel

This article is a response to a paper presented at the sixth International Workshop on Power Definitions, a report that rejected the fact that the Poynting vector (PV) provides useful information “for academic interpretation of power properties and for practical applications of power theory”. This study explains how the PV reveals the existance of power oscillations unexplained by simple mathematical models used in the basic circuit theory.

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A Hybrid Reference Signal Generator for Active Compensators

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Herbert L. Ginn III

A new reference generation technique for active compensators based on the use of CPC theory along with the instantaneous reactive power (p-q) theory is presented here. Modifications to reference signal generation techniques based on instantaneous reactive power as well as to the synchronous reference frame (d-q) method are proposed. The proposed strategy utilizes the CPC theory instead of the filters typically used to extract the desired components of the current.  

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Current’s physical components theory and p-q power theory in the control of the three-phase shunt active power filter

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Andrzej Firlit

This paper presents the comparison among the control algorithms of a three phase, three wire shunt active power filter. The control algorithms are based on: 1.the current’s physical components theory; 2 the p-q power theory. The active power filter operation under the distorted supply voltage at the point of common coupling condition is considered. The comparison concerns the aspects of: filtering current harmonics, reactive power compensation (defined in the fundamental harmonic domain), supply current balancing and dynamic performance.

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Performance Evaluation of a Multifunctional Energy Metering IC under Sinusoidal and Non-Sinusoidal Conditions

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Gaetano Pasini, Lorenzo Peretto, Elisa Pivello, Roberto Tinarelli

Low-cost handheld instruments performing a large variety of electrical measurements are recently appeared on the market. Their diffusion is mainly due to the availability of integrated circuits that carry out many measurement functions, thus simplifying the instrument implementation and reducing the costs. In this paper, the accuracy performances of an integrated circuit featuring rms and power measurements are evaluated under both sinusoidal and non-sinusoidal conditions.

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