bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of fuzzy inverter control
Authors: Lin B.‐R. 
Published: July 2010

AbstractModern static UPS (uninterruptible power supply) must exhibit great stability, high transient response to load variations and high reliability. It must also be characterized by compactness, light weight, AC input harmonic current reduction, output voltage distortion reduction and low cost. A new control method for real‐time digital control of the single‐phase pulse‐width‐modulation (PWM) inverter for UPS applications is presented. An approach for combining the deadbeat control and the fuzzy logic compensator is proposed. Using the state variables measured at every sampling time, the controller calculates the inverter pulse width for the next sampling time. The fuzzy logic controller is used to compensate the voltage drop due to non‐linear loads. The proposed control scheme is verified by simulations for non‐linear load conditions, sudden load changes and system‐parameter variations.
Closed‐form solution of a three‐phase vsi feeding a three‐phase static inductive load
Authors: Abdel‐Halim I. A. M. , Hamed H. G. , Slama M. M. 
Published: July 2010

AbstractIn this paper, a closed‐form solution of the performance of a three‐phase voltage‐source, six‐step inverter feeding a three‐phase static inductive load is presented. Analytical expressions for the steady‐state currents of the system are derived from which the performance of the system can be investigated. Explicit formulae for the current ratings of the switching elements, whether thyristors, transistors or diodes used in the system are derived.
Theory and design of a space‐vector modulator for ac‐ac matrix converter
Authors: Neacsu D. O. 
Published: July 2010

AbstractA new PWM algorithm for AC‐AC matrix converter derived by a vectorial analysis is presented. In addition to the development of the basic principles, the paper includes simulation results that confirm the validity of this analysis. This new Space‐ Vector PWM strategy can be generated on‐line in real time using a simple microprocessor software algorithm which is discussed. The resulting Space‐ Vector PWM is also representing a unified model for Space‐Vector Modulation strategies suitable for the particular situations of either voltage‐ or current‐source inverters or rectifier bridge.
A simplified real frequency independent modal transformation for overhead line switching transient computations
Authors: Papagiannis G. , Dokopoulos P. 
Published: July 2010

AbstractModal transformation technique is a common tool for transmission line transient computations. A simplified modal decomposition of overhead transmission lines, suitable for time‐domain switching (up to 105 Hz) transient computations, is proposed. By neglecting residual terms in the ZY matrix, transformation matrices are approximated as real and frequency independent. The resulting propagation constants remain unaffected from the line being transposed or not, although the existing asymmetries affect transformation matrices. The method can be extended for double circuit lines, provided they have the same configuration. Propagation characteristics, mode decoupling and travelling‐wave transmission effects have been investigated. Results are compared with those obtained from other methods in use.
Multiagent fault‐diagnosis expert system in power systems
Authors: Wang J. P. , Trécat J. 
Published: July 2010

AbstractIn order to solve the speed problem and shallow reasoning problem met in current research in fault diagnosis expert system, this paper presents a model based parallel fault diagnosis expert system for energy management systems (EMS). The Petri net model, which corresponds to the relationship between power system components and their protection systems, has been used for the inference in fault diagnosis. A multiagent parallel processing expert system, which is based on five transputers in Sun workstation, has been built for fault diagnosis purposes. The test results show that this expert system is not only fast but also has better performances.
A non‐linear programming approach based on quasi‐newton techniques for optimization of power systems
Authors: Lei X. , Povh D. , Kulicke B. 
Published: July 2010

AbstractNETOMAC program is one of the most powerful software systems which has been widely used for the simulation of power systems. In order to solve various non‐linear optimization problems arising in power systems, an optimization algorithm based on the Quasi‐Newton Technique is presented in this paper. The algorithm that works as a special mode of the simulation program can be flexibly used to most describable non‐linear optimization problems either static or dynamic, and provides acceptable solutions under the consideration of all possible operational and security constraints. The algorithm offers substantial improvements in practical applications mainly due to adaptive scaling by heuristic considerations of the variable, handling the bound constraints directly with an efficient quadratic programming approach and using a modified augmented Lagrange multiplier method to deal with the functional constraints. The paper concludes with the three application examples for solving different optimization problems of power systems.
Critical evaluation of ansi pollution test for multi‐unit metal‐oxide surge arresters
Authors: Aradhya R. S. Shivakumara , Gururaj B. I. , Ramamoorty M. 
Published: July 2010

AbstractStandardization of pollution testing of metal oxide surge arresters (MOA) is being attempted by different research groups throughout the world through field tests and laboratory investigations. The non‐uniform wet contamination method of ANSI standard C 62.11, 1987, which is reported to have good repeatability for temperature rise during laboratory tests, has been adopted by many countries including India. Also, much work is being done in some European countries on other methods. This paper gives a critical analysis of the ANSI method based on results of computer simulation studies and supporting laboratory tests. The sensitivity of the arrester element temperature rise on the atmospheric humidity during ANSI tests and possibility of representing the site severity have been established for the first time. It is concluded and suggested that to further improve the repeatability of ANSI test results, it may be desirable to stipulate a range of atmospheric humidity levels in the laboratory which may be of the order of 70 % to 80 %.
Distance protection of unsymmetrical lines
Authors: Hupfauer H. , Schegner P. , Simon R. 
Published: July 2010

AbstractTechnical, economical and ecological aspects lead to untransposed power lines. Full transposition schemes are often to expensive and not applicable to short poly‐circuit lines. Therefore line unsymmetry is of importance with respect to the impedance calculation and the setting of distance‐protection relays. As a consequence of line unsymmetry the short‐circuit impedance depends on the fault type and the measuring loop. As conventional distance protection is based on the model of a symmetrical line, this causes an unsharpness of the tripping area in the complex impedance plane. To avoid wrong tripping, distance‐protection relays must be set with reduced ranges. Consequently, the fault clearing time increases for extended sections at both line ends. Furthermore fault localization ‐ an additional feature of increasing importance ‐ will be as inaccurate as the measured impedance. Improvement of distance measurement by new current‐compensation methods are discussed in this paper. Extensions of the methods to mutual coupled double‐circuit lines are outlined.
Reliability evaluation of highly reliable computer control systems for energy generation, transmission and distribution
Authors: Kochs H.‐D. , Dieterle W. , Dittmar E. 
Published: July 2010

AbstractThe paper presents the results of an application‐based reliability study of distributed computer control systems with very high reliability demand, e.g. for supervision and control of power plants and energy distribution systems. A reliability classification scheme is presented and typical redundant control system structures are evaluated and classified due to their system reliability. Special focus is placed on assessing the influence of the communication system on total system reliability.
Performances of high‐voltage glass insulators subjected to fast transient overvoltages
Authors: Femia N. , Lupò G. , Petrarca C. , Tucci V. , Vitelli M. 
Published: July 2010

AbstractSteep‐front, short‐duration voltage pulses occur in power systems as a consequence of lightning, switching of the increasingly used gas‐insulated switchgears or by electromagnetic pulses of very high amplitude. Such overvoltages characterised by very fast rise time may produce irreversible damages to the insulation of the different apparatuses of an electric power line. Test results will be presented in this paper concerning the behaviour of cap and pin‐glass insulators subjected to steep‐front overvoltages. In particular, the effect of the glass composition on the insulator performance will be analysed for both normal and anti‐fog configurations. Moreover, the dependence of the test results on the polarity of the applied voltage and the electrodes arrangement will also be discussed.
Open‐loop speed calculation in stator‐fixed reference frame
Authors: Németh‐Csóka M. 
Published: July 2010

AbstractThis paper presents two possible ways for calculating the speed of an induction machine without using any mechanical transducers. The proposed methods are based only on measured electrical quantities. A machine model is used where the rotor flux is calculated from the statorflux and the measured current. The generally valid forms are tested with Direct Self Control. The simulated performance of the proposed method together with the start‐up of an already rotating machine is included.
Analysis of high‐frequency PWM techniques suitable for resonant inverters
Authors: Neacsu D. O. , Alexa D. 
Published: July 2010

AbstractSpecial Pulse‐Width‐Modulation (PWM) techniques capable of realizing true PWM operation of quasi‐resonant DC‐link inverters are presented. These techniques provide an increased value of the lowest switching time for higher carrierfrequencies. The harmonic performances are extensively studied by simulation in comparison with conventional Space‐Vector Modulation and a simple algorithm for real‐time implementation is developed.
Modelling and simulation of unsymmetrical supplied three‐phase induction motor
Authors: Zuckerberger A. , Alexandrovitz A. 
Published: July 2010

AbstractA general mathematical model of a three‐phase symmetrical induction motor expressed by means of state equations with line‐to‐line voltages as input variables is presented. Such a model permits the analysis of the dynamic behaviour of the motor supplied with unsymmetrical sinusoidal or non‐sinusoidal voltage wave‐forms. Simulation programs were written by means of MATLAB/Simulink software package. The presented model was used to simulate transient behaviour of the motor with unsymmetrical supplied voltages and its operation when fed from a symmetrical source (the mains) and from a six‐step inverter. A mathematical model representing the induction motor operated with one phase disconnected was developed and simulated. Experimental results were compared with the simulated ones and good resemblance was observed.
Main flux‐saturation modelling ind‐qaxis models of induction machines using mixed current‐flux state‐space models
Authors: Levi E. , Krzeminski Z. 
Published: July 2010

AbstractMain flux saturation in induction machines is most frequently modelled by selecting either stator and rotor d‐q axis currents or stator and rotor d‐q axis flux linkages as state‐space variables. This paper deals with so‐called mixed current‐flux state‐space models where either stator or rotor current space phasor is selected as one state‐space variable. The other state‐space variable is one of the three flux‐linkage space phasors in the machine (stator, magnetizing or rotor), so that six different state‐space models are encompassed. A generalised derivation procedure for all the six models is at first presented. Models are further given in developed form. It is shown that cross‐saturation effect is explicitly present in all the models. Derivation procedure and the models are verified by simulation and experimental investigation of induction generator self‐excitation.
Mathematical foundations of the instantaneous power concepts: A geometrical approach
Authors: Willems J. L. 
Published: July 2010

AbstractIn this paper a mathematical formalism, based on a geometrical approach, is proposed for defining the concepts of instantaneous active and instantaneous reactive power. Use is made of the dot product and the cross product for three‐dimensional vectors. The relationship with the analysis proposed by Akagi et al. and by Ferrero and co‐authors is discussed in detail. In particular it is shown that the proposed formalism is well suited to deal with three‐phase currents and voltages with zero‐sequence components.
Dynamic on‐line measurement of equivalent parameters of three‐phase systems for harmonic frequencies
Authors: Czarnecki L. S. , Staroszczyk Z. 
Published: July 2010

AbstractA method of an on‐line measurement of equivalent parameters for harmonic frequencies of a three‐phase distribution system with harmonic generating loads is discussed in the paper. The impedances of the supply and the load, the complex RMS (CRMS) values of the load generated current harmonics, and the CRMS values of the distribution voltage harmonics are the subject of the measurement. It is shown that the on‐line measurement of these parameters requires that the line voltages and currents are measured at least in three different states of the system. These states of the tested system are changed by disturbing the system with a current harmonics generating device, built in a form of a fast thyristor switch. The method is illustrated with measurements in a physical system.
Criteria for the definition of the electric power quality and its measurement systems
Authors: Tugulea A. 
Published: July 2010

AbstractAn attempt to define the quality of physical and technical processes in general and of electric energy in particular is given, by considering the two main meanings of the quality: a set of properties and characteristic, a degree of excellence. It is emphasized the main role of the conservative parameters of quality. A Data Aquisi‐Hon System (DAS) for the monitoring of electric power quality is proposed and some results of measurements are given.
Some possible new applications of a partial‐discharge (PD) model and its relation to PD‐detection sensitivity
Authors: Danikas M. G. 
Published: July 2010

AbstractIn this paper some possibilities of further applications of a known “Streamer Partial‐Discharge Model” are proposed. These possibilities refer to the relation between the observed partial‐discharge (PD) magnitude and the applied field to the insulation. Furthermore, the model is a useful tool to investigate the sensitivity of a PD detector and also to compare the sensitivities between various PD detectors.
Time‐varying loads in electric power systems: Power input, equivalent circuit elements, and disturbances
Authors: Knoop M. , Köhle S. 
Published: July 2010

AbstractTime‐varying electric loads, fluctuating around their nominal point, cause fluctuations also of current and power. The mean phasors of current and complex power differ from their nominal values, which results in a deflection of mean power input. A transformation to a time‐invariant equivalent circuit is introduced representing the mean values of voltage, current and power. The variances on the other hand contribute equations for a second phenomenon of fluctuating loads: the generation of disturbances in the power supply system. Results for both phenomena are derived for single‐phase loads, validated by Monte‐Carlo simulations, and generalized to three important kinds of three‐phase loads. Measured data from an electric arc furnace illustrate the application of ideas.
A chemical approach to the dielectric aging of fibre‐reinforced polymer (frp) insulators
Authors: Schrijver C. , Herden A. , Kärner H. C. 
Published: July 2010

AbstractA time‐based model for the water‐influenced dielectric aging of FRP is presented, using chemical mechanisms to explain the measured increase of the loss tangent and the dielectric constant as well as the interphase orientation of the electrical breakdown channel in FRP insulators. Although this hypothesis is founded on artificial and accelerated aging of FRP specimens, it is also representative for real outdoor conditions. The model consists of three phases: I. water penetration by anomalous diffusion, leading to a weak increase of the dielectric parameters, 2. hydration of generated metal ions, causing a slight decrease of the dielectric constant and a strong increase of both, the loss tangent and the interphase conductivity and 3. a loss of adhesion, resulting in a strong increase of both, the dielectric parameters and the local electrical conductivity.
Enhanced selectivity and fault detection for distance protection in meshed grids by evaluating local 50‐hz‐phasors
Authors: Zettler K.‐R. 
Published: July 2010

AbstractDue to different operating conditions distance protection units measure varying short‐circuit impedances (impedance uncertainty) and with that varying fault locations for one and the same short circuit. Therefore, it is necessary to reduce the reach of the respective time zones to avoid unwanted relay operation. This, however, may lead to an undesirable long fault clearance time. For the first time zone an optimal uncertainty minimizing strategy is presented based on pre‐fault power measured at the relay. For back‐up protection a method is proposed that minimizes the impedance uncertainty with the help of symmetrical components. As a result of meshed grids, the problem is often to detect short circuits in higher time zones on the whole. To cope with that problem a simple method is discussed, which allows an optimal distinction between load and fault states.
Accident control and stability of a pv induction motor pump set
Authors: Khashab H. El , Motaleb M. S. A. El 
Published: July 2010

AbstractThis paper presents a proposed algorithm for controlling an induction motor pump set powered from photovoltaic (PV) generator through a current source inverter. In particular, problems related to the efficiency of induction motors have received much attention due to their wide applications. An improved constant flux control system is used to optimize the motor efficiency by reducing the air‐gap flux. From an other interesting point of view, the reduced air‐gap flux may result in undesirable dynamic responses. In order to overcome this drawback, an accident stability region is designed using the eigenvalues‐zero pattern with the necessary linearization procedures.
Rotor‐field orientation with optimal torque‐control strategy for current‐fed induction‐machine system
Authors: El‐Sayed I. F. 
Published: July 2010

AbstractField orientation provides the possibility to control torque and flux of the induction machine independently. However, the widely used control strategy for field orientation is based on constant rotor flux. This strategy does not utilize all advantages by using field‐orientation method. This paper reveals a degree of freedom for controlling an induction machine, by controlling both field‐ and torque components. It presents a control strategy based on varying the flux level to provide optimum torque operation irrespective of speed ranges. The freedom for controlling both field‐ and torque components of the stator winding currents can make the inverter induction motor drive superior to DC drives, where proper resolving for the stator current components can provide maximum electromagnetic torque per ampere, optimal efficiency and higher short duty system capability. In this paper, the rotor‐field oriented saturated model of the induction machine is presented. The analysis of the electro‐magnetic torque, in terms of stator current components, is used to find the optimal resolving ratio for maximum torque. This optimal ratio depends on the machine parameters and the saturation level. Investigation and comparison for widely used and the proposed control strategies are given for different cases, namely: neglecting saturation effect case, then taking saturation into account for low‐ (0.75 kW) and high power rating (90 kW) machines. Also, the proposed optimal control strategy and the microprocessor implementation method are presented.
Sensor‐less, neuronal‐network‐based cage defect diagnosis for induction machines
Authors: Blattner J. , Gutt H.‐J. 
Published: July 2010

AbstractThis paper presents a PC‐based diagnosis system for cage defects in squirrel cage induction motors. Second‐order effects, like field and voltage harmonics, core currents and torque ripple caused current sidebands are integrated in a novel machine model for cage defects. In addition, the harmonic analysis display a way how the machine speed can be calculated out of the current spectrum. The experimental test of the diagnosis system reveals not only the ability to diagnose a defect cage, but also to distinguish different kind of defects.
Model to describe the chemical ageing behaviour of electrical busbar joints
Authors: Bergmann R. , Löbl H. , Böhme H. , Großmann S. 
Published: July 2010

AbstractElectrical joints are subjected to an ageing process which can endanger the reliability of electrical power transmission systems. A mathematical model is presented with the help of which the ageing behaviour of electrical joints can be estimated depending on the conductor material, the construction of the joint, the assembly technology and the loading construction. The model is based on theoretical reflections as well as practical investigations on busbar joints for more than 16 years.
Prediction of the steady‐state performance of the switched reluctance motor using quadratic BIEM‐FEM field solutions in the linear model
Authors: Omekanda A. , Broche C. , Crappe M. , Baland R. 
Published: July 2010

AbstractPrediction of the steady‐state performance of a switched reluctance motor (SRM) becomes complicated because of the complex influences between the motor parameters and excitation current. Accurate calculation of the electromagnetic quantities required for an SRM steady‐state prediction is not easy because these parameters are affected by intense saturation of the corners of partially overlapping stator and rotor poles. This paper presents a quadratic boundary‐integral equation (BIE) finite‐element (FE) method that has been proved accurate for the calculation of the motor parameters. The linear model of an SRM based on a trapezoidal evolution of a phase inductance versus rotor position for a constant excitation current is exploited. The instantaneous phase current and the average torque in the SRM angle‐controlled modes of operation are computed using the results of the BIE‐FE method with the analytical solution of the electrical differential equation describing the SRM drive. The prediction of the total average torque in a steady‐state angle‐controlled mode of a SRM drive operation agrees favourably with experimental results.
A method for probabilistic harmonic load‐flow analysis in power systems
Authors: Lehtonen M. 
Published: July 2010

AbstractA new probabilistic method is presented for the harmonic load‐flow analysis in electrical power systems. In the method, the network is modelled using the bus impedance matrix at each harmonic order. The load flow is solved by a current injection method. For harmonic sources, the amplitude variation and the phase angle variation are taken into account. For the summation of the harmonics originating from different sources, a probability density function, derived from the jointly normal distribution is used. As a final result, statistical estimates are obtained for the node voltages and branch currents of each harmonic frequency considered.