bluuebunny/crossref_metadata_2025_split huggingface dataset:
An improvement of the iterative harmonic analysis method
Authors: De Martinis U. , Fantauzzi M. , Testa A. 
Published: July 2010

AbstractThe paper proposes an iterative method as a possible improvement of the classical power system harmonic analysis method known as IHA (Iterative Harmonic Analysis). Such improvement is indicated when convergence problems occur as consequence of supply system resonances, low short‐circuit ratios or strong interactions in the operation of non‐linear devices. The iterative method proposed is described and then some considerations on its accuracy and computational efficiency are carried out. Finally numerical experiments referring to single converter as well as multi‐converter installations are reported to show the applicability and the usefulness of the iterative method proposed.
Measurement of Arc‐root velocity of magnetically driven Arcs in switchgear
Authors: Worzyk Th. B. 
Published: July 2010

AbstractThe arc‐root velocity is an important parameter in switchgear devices using magnetically driven arcs for current interruption. Optical measurements of the arc movement may be difficult to accomplish without changing the switchgear device. A simple electrical method for determination of the arc‐root velocity is described in this paper. The arc‐root velocity is represented by the frequency of an electrical signal which makes the measurement highly unaffectable by the harsh electromagnetic environment usually found in switchgear subjected to power tests. The arc‐root velocity can be measured close to the current‐zero passage which is decisive for successful current interruption.
Pilot‐bus selection for secondary voltage control
Authors: Conejo A. , Gómez T. , de la Fuente J. I. 
Published: July 2010

AbstractThe secondary voltage control determines control device actions based on reference voltage values set at certain load buses denominated pilot buses. A key factor for the appropriate functioning of secondary voltage control schemes is the selection of the pilot buses. This paper addresses this problem taking into account system‐wide information, and different operating conditions regarding different load levels and different network topologies. The proposed approach improves previous approaches in two respects: the level of modelling detail and the computational efficiency. Two case studies based respectively on the IEEE 118‐bus system and the New England 39‐bus system are provided.
Vulcanization influence on TSD currents and wettability of room temperature vulcanized silicone rubber hv insulator coatings
Authors: Gubanski S. M. , Wang M.‐S. E. 
Published: July 2010

AbstractThermally Stimulated Depolarization (TSD) current spectra and surface wettabilities, represented by contact angles, i. e. the advancing angle and the receding angle, were measured on two types of high voltage room temperature vulcanized silicone rubber coatings during their vulcanization processes at room (25°C, 80 % RH) and elevated (70°C, 80 % RH) temperatures. Results show increases in the material hydrophobi‐cities with the vulcanization degree until their stabilized values are reached. Compared with the room temperature vulcanization, the elevated temperature speeds up stabilization processes of the contact angles and of the TSD spectra. Variations of the contact angle seem to be closely related with changes of the TSD peaks. In most of the cases, the contact‐angle increase is accompanied by either the TSD peak‐height decrease or the peak‐temperature increase.
Dynamical model for electrical aging of a solid dielectric
Authors: Fantana N. L. , Böhme H. 
Published: July 2010

AbstractIn the paper the possibility to gain a qualitative insight into long‐time phenomena in dielectric materials, using a dynamical model, is investigated. It assumes a simplified micro structure of the material and a set of rules which apply iteratively. The rules describe some basic features of the aging phenomena under partial discharge. Stochastic aspects were modelled by using random number generators. Simulation was carried out for various starting microstructures regarding number, size and position of initial voids and for different applied voltages.
On‐line tuning of the rotor resistance in an inverter‐fed induction machine with direct‐self‐control
Authors: Klaes N. R. 
Published: July 2010

AbstractThis paper describes a simple adaptive torque‐balancing controller/or on‐line tuning the rotor‐temperature dependent rotor resistance in an inverter‐fed induction machine. The identification has been especially designed for use in drives with Direct‐Self‐Control. The basic version works well down to stator frequencies of a few Hz, even under transient conditions and without stator voltage sensors, but only with a DC‐link voltage sensor. It is shown that the basic version can be enhanced to work properly not only at locked rotor but even at stationary zero stator frequency except for no‐load operation. Then the information for tuning the rotor resistance at zero or very low stator frequencies is obtained by low‐frequency modulation of the stator flux magnitude and observation of the torque of a parameter‐sensitive observer concerning modulation frequency related oscillations, which occur only in the case of a mismatched rotor‐resistance parameter. The parameter is tuned via a simple l‐controller until the oscillations vanish. Experimental tests at a standard 66‐kW squirrel‐cage motor prove the excellent performance of the proposed method.
Reduction of machine current distortion using direct self control (dsc) for high‐power three‐level gto‐inverters
Authors: Hoffmann F. , Springmeier F. 
Published: July 2010

AbstractDirect Self Control (DSC), developed for voltage‐source inverter‐fed induction motors, is an efficient and highly dynamic control method for inverters in the MW‐range with a limited switching frequency up to 200 Hz… 250 Hz, It is based on control ofstatorflux in a stator‐fixed reference frame; in the region below rated statorfrequency a two‐level torque controller adjusts the voltage directly so that no Pulse‐Width Modulation (PMW) is necessary. Three‐level inverters, which are best suited for very high voltage and high power demand, have several additional advantages compared to two‐level inverters, e. g. the pulsation of torque can be reduced as well as the machine current distortion. In this paper an improved two‐level torque control strategy for three‐level inverters with less current distortion is described and the practical results of its application based on measurements at a 22 kW experimental machine set are discussed.
Line‐side behaviour of three‐phase diode rectifiers with reactance smoothing
Authors: Grötzbach M. , Xu J. 
Published: July 2010

AbstractThis paper describes the line‐side behaviour of three‐phase diode rectifiers depending on AC‐ or DC‐side smoothing reactances. The special case of DC reactance only is investigated analytically by the aid of switching functions, showing basic dependencies for neglected commutation effects. The generalized case of AC‐and DC‐side reactances must be solved iteratively, whereby a significant reduction of the evaluation effort is achieved by a set of analytical equations. All results are presented in uniform diagrams to allow a comparison of both reactance locations. It results that DC‐side smoothing is advantageous with respect to the behaviour of the fundamental and 5th line‐current harmonic, whereas A C‐side reactances are leading to lower amplitudes for all other harmonics. In case of DC smoothing reactance, even small AC reactances influence the line‐side behaviour significantly.
An algorithm for the dimensioning of circuits for synthetic high‐voltage circuit‐breaker testing
Authors: Witte G. 
Published: July 2010

AbstractThe paper addresses to the design of high‐voltage circuits for synthetic circuit‐breaker testing. After a presentation of two different test circuits, a general cost function is defined, which has to be minimized in order to get the best combination of elements for these circuits. The applied algorithm is described in combination with a network calculation program as a method in order to automate the design of synthetic test circuits.
Increasing the efficiency of high‐speed solid‐rotor induction machines
Authors: Pyrhönen J. , Kurronen P. 
Published: July 2010

AbstractBecause of its simple structure a solid rotor is cheap and robust and so a very good alternative to be used in high‐speed induction motors. Traditionally the disadvantage with solid‐rotor motors has been a quite poor efficiency. This paper studies some possibilities of increasing the efficiency of a high‐speed solid‐rotor induction machine both in theory and practice.
Capacitive coupling through the shields of medium‐voltage cables
Authors: Braun A. 
Published: July 2010

AbstractThe shield ofmedium‐voltage‐XLPE cables is in general not a metal tube, but consists of several copper wires lying on the outer crepe paper above the insulation. This configuration allows a capacitive coupling between the cable conductor and external conductive objects. In this paper a theoretical consideration of the capacitive coupling using an analytical solution is described and the validity of the results is proofed with numerical methods. For several arrangements the quantity of the capacitive coupling is determined.
Analysis and design of a combined system of shunt passive and active filters
Authors: Caramia P. , Carpinelli G. , Gagliardi F. , Verde P. 
Published: July 2010

AbstractPassive and active filters have traditionally been used to reduce harmonics in power systems. Only recently combined systems of shunt passive and active filters have been proposed in order to overcome the technical problems of passive filters and to reduce the costs of active ones. The paper tries to overcome some drawbacks of a combined filtering system (modified high‐pass filter) which appeared in literature. In particular, improvements in the system structure and in the steady‐state design methodology are proposed to obtain a filtering system with both satisfactory compensation characteristics and low costs. Finally, numerical applications are discussed considering a test case.
Numerical fault arc simulation based on power arc tests
Authors: Kizilcay M. , Koch K.‐H. 
Published: July 2010

AbstractMore than 200 power arc tests were carried out with original arrangements of overhead line insulators and arcing fittings for 20 kV, 110 kV and 220 kV. With an adequately modelled network, short‐circuit currents in the range of 2 kA to 12.5 kA can be realized. Analysis of the measurements shows that a typical arc voltage time function can be attributed to each insulator type and arrangement. Using the measured variables, which were digitally recorded and stored on optical media, an existing numerical arc model has been enhanced, which can be applied in an electromagnetic transients program to reproduce the dynamic and random behaviour of power arcs for any insulator arrangement, current and system voltage.
Behaviour of harmonic current vectors generated by six‐pulse ac/dc converters as function of plant parameters
Authors: Cavallini A. , Loggini M. , Montanari G. C. 
Published: July 2010

AbstractIn the paper an investigation on the behavior of six‐pulse AC/DC converters is presented, with the aim of studying the influence of plant and load parameters on harmonic currents injected by converters in A C networks. By means of a piece‐wise linear approach, the analytical solution of steady‐state currents is achieved and AC current waveform is built up. In this way, several cases with different plant parameters can be processed in reasonable computer times, and indication on plant‐parameters optimization is achieved. Comparisons are made with the approximate method, often employed to evaluate AC harmonic current amplitudes, and considered the “worst‐case” to this purpose, which resorts to Fourier series decomposition of a rectangular AC‐current waveshape.
Four‐level dc to dc converter for high‐voltage applications
Authors: Schülting L. , Posluszny M. , Platek T. 
Published: July 2010

AbstractThe motivation of different developments concerning multi‐level converter has two origins. In high‐power applications this technique enables among others low harmonic distortions. In addition the voltage stress of the semiconductor devices can be reduced in high‐voltage applications. This article describes a theoretical analysis, design considerations for the active and passive elements and a control method of a four‐level DC to DC converter for high‐voltage applications. The calculations and the control method are compared with measurements made in the laboratory.
Magnetic saturation in rotor‐flux‐oriented induction motor drives: operating regimes, consequences and open‐loop compensation
Authors: Levi E. 
Published: July 2010

AbstractParameter variation effects infield‐oriented induction machines can cause significant performance deterioration. Magnetic saturation of the main flux path is one of the sources of parameter variations, caused by non‐linear nature of the magnetizing curve. The paper at first discusses operating regimes of a rotor‐flux‐oriented machine which lead to operation with variable main flux in the machine. These are shown to be operation with variable stator d‐axis current command during forced excitation and in field‐weakening region, and operation with variable q‐axis current command during rapid speed changes when cross‐saturation effect causes variable main flux operation. Actual effects of variable saturation level on performance of the drive are assessed by simulation. Modified rotor flux estimation schemes are then derived, which enable instantaneous open‐loop adaptation to actual saturation degree in the machine. The proposed adaptive rotor‐flux estimators are verified by simulation and some experimental results are included as well. As the saturated induction machine representation is based on the current state‐space model, while the modified rotor‐flux estimator relies on the flux state‐space model, the performed simulation study shows that current state‐space model and flux state‐space model, although considerably different in their appearance, account for the main flux saturation in basically the same way.
Method of the air‐gap electromagnetic torque identification for a current‐fed ac drive system
Authors: Kulski† Z. H. 
Published: July 2010

AbstractThis paper presents a simple method of determining the air‐gap electromagnetic torque for the current‐fed induction motor. The identification procedure uses the measurement and processing the electrical terminal values of the inverter without participation of the drive motor parameters. This method uses the current‐oriented component of the air‐gap magnetic flux and the input current of the inverter. The identification of the inverter output phase in the non‐conducting state has made it possible to use the motor working windings for a direct measurement of the stator source voltage. The method which has been explained enables the standardization of the procedure of signal processing for a wide class of converter drive systems with the A C motors. The effectiveness of this identification procedure is illustrated by the laboratory test results.
A techno‐economic design study of high‐temperature superconducting power transmission cables
Authors: Ashworth S. P. , Metra P. , Slaughter R. J. 
Published: July 2010

AbstractThe results of a comprehensive techno‐economic design study of power transmission cables utilising High‐Temperature Superconductors are presented. A cable design is described, based upon superconductors operating at liquid nitrogen temperatures. The dimensions and operating parameters of an optimized underground cable are calculated. Based on this design the manufacture, installation, losses and operating costs of an AC High‐Temperature Superconducting (HTSC) Cable are estimated and compared with conventional underground cables for a new power link. Significant conclusions of the study are: for transmitted powers greater than I GVA the HTSC cable transmission costs become the same as for conventional cables when the superconductor critical current density exceeds 200 kA/cm' at liquid nitrogen temperature; the HTSC‐based cable is capable of transmitting up to seven times as much power (to 700 MVA at 66 kV) as a conventional cable in a 150 mm fixed diameter duct at the same transmission cost.
Optimal compensator currents for the reduction of the harmonic distortion in networks part 1: analytic solution
Authors: Dai X. , Gretsch R. 
Published: July 2010

AbstractFast harmonic compensators have been developed and will come into practical use in power systems for the reduction of harmonic currents exchanged between an installation and the feeding network or for the reduction of the voltage distortion at a single node, e. g. a central bus. In order to reduce the harmonic voltage level of an entire network a special strategy is necessary to optimize the compensator current injected into the node. The optimization problem consists in finding the minimum of the proper objective function, which can be defined e. g. as the quadratic sum of the harmonic voltages at all network nodes or of the harmonic currents in all network branches. In addition constraints such as the rated compensator current or/and the limitation of nodal harmonic voltages have to be observed. The proposed solution considers stepwise (I) a single compensator for only a single harmonic order, (II) a single compensator for multiple harmonic orders, and (III) several compensators spread over a system for a single or multiple harmonic orders. The analytic solution, in the first step under at maximum one constraint, is presented in this paper. The validity of this method has been verified by the simulating computation for a real simplified 20 kV distribution system.
Optimal compensator currents for the reduction of the harmonic distortion in networks part 2: graphic solution
Authors: Dai X. , Gretsch R. 
Published: July 2010

AbstractA graphic method to optimize the compensator current which is injected into a network node in order to reduce the harmonic distortion of the network, for the single‐order harmonic problem, is presented. This method is suitable to find out whether a solution of the optimization problem, even under multiple constraints, exists and, in this case, gives the approximate optimum. Since this graphic solution is easily executed by computer, it seems to be an attractive and practicable technique. Its validity and simplicity has been verified by the simulating computation for a real simplified 20 kV distribution system.
Vulcanization influence on tsd currents and wettability of room temperature vulcanized silicone rubber hv insulator coatings
Authors: Danikas M. G. , Gubanski M. 
Published: July 2010

AbstractThis paper deals with the Thermally Stimulated Depolarization (TSD) current and contact angle measurements on Room Temperature Vulcanized (RTV) silicone rubber High‐Voltage (HV) insulator coatings taken recently by Dr. S. M. Gubanski and Dr. M.‐S. E. Wang.
Instantaneous sinusoidal and harmonic active and deactive currents in three‐phase power systems
Authors: Willems J. L. 
Published: July 2010

AbstractIn this contribution a new decomposition of sinusoidal three‐phase currents is proposed. The main feature is that it leads to the compensation of non‐active currents partly by elements without energy storage and partly by means of linear elements with energy storage (inductors and capacitors). The proposed decomposition is compared with existing procedures, such as those developed by Akagi‐Nabae and by Czarnecki. The possible generalization of this concept to distorted voltages and currents is discussed.
Measurement aspects of the voltage distortion compensation
Authors: Mikolajuk K. , Staroszczyk Z. 
Published: July 2010

AbstractA complete solution of the compensator controller, allowing to eliminate voltage distortion in power system is presented. The two‐step circuit identification procedure based on the interpolating “Fast Fourier Transformation “ (FFT) has been successfully used to damp the 3rd, 5th and 7th harmonic by 60 dB at selected buses. Interpolating, flat‐top and coherent sampling methods, when used to 10 bit A/D converted (noised) signals, have been compared and simulated. It is shown that the shortest signal record requested to perform step calculations is of only one voltage period when a modified windowed coherent sampling method is used. The proposed method is tolerant to the coherency mistuning, so easy to implement even if a very simple hardware frequency multiplier is used to generate the sampling signal. A background to the presented solutions is given, allowing easily to solve similar compensating problems with different constraints.
Comments on “apparent power ‐ a misleading quantity in the non‐sinusoidal power theory: are all non‐sinusoidal power theories doomed to fail?”
Authors: Czarnecki L. S. 
Published: July 2010

AbstractIt is shown in this comment that recent development in the power theory of systems with non‐sinusoidal waveforms contradicts the conclusions presented in the paper “Apparent Power ‐ a Misleading Quantity in the Non‐Sinusoidal Power Theory: Are all Non‐Sinusoidal Power Theories Doomed to Fail? “ published by P. S. Filipski in ETEP 3(1993), no. J,pp. 21‐26. That paper deforms the history of the power theory development and its present state. Moreover, the notion of ‘power theory’ should not be associated with a particular power equation, but be comprehended as a knowledge base on power properties of electric circuits, revealed with various approaches. The comment discusses also the notion of ‘apparentpower’ as a conventional quantity.
Evaluation of instantaneous power terms in multi‐phase systems: techniques and application to power‐conditioning equipment
Authors: Rossetto L. , Tenti P. 
Published: July 2010

AbstractThis paper presents a general control method that fully utilizes the inherent capability of AC‐fed PWM converters to compensate for reactive and harmonic currents absorbed by other loads. For this purpose, suitable definitions of instantaneous active and reactive current and power terms are introduced. Simulated results demonstrate the capabilities of the proposed compensation method, which can also be implemented in existing systems, as only modifications of the control section are needed.
Parallel‐in‐time method based on shifted‐picard iterations for power system ty‐ansient stability analysis
Authors: Brucoli M. , De Roma A. , La Scala M. , Trovato M. 
Published: July 2010

AbstractThe transient stability analysis is the most time‐consuming computer simulation in power system studies. For this reason, in recent years, parallel processing has been applied for implementing on‐line time‐domain simulations of power system transient behaviour. As is well known, the problem of power system transient simulation consists, basically, in the solution of an initial value problem for a mixed set of Ordinary Differential Equations (ODE) and algebraic equations. The objective of this paper is to present an algorithm based on Shifted‐Picard dynamic iterations, which solves the above mentioned set of non‐linear Differential Algebraic Equations (DAE) by the iterative solution of a linear set of DAE. This feature is important because the time behaviour of the linear set of differential equations can be obtained by the solution of an integral. In this case, a multiprocessor parallel‐in‐time implementation of such algorithms is possible because each processor is devoted to the evaluation of the required variables relative to each time step. Moreover, parallelism‐in‐time allows multigrid techniques to be implemented in a natural way. Test results on realistic‐sized power systems are presented.