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Harmonics and Quality of Power Proceedings, 1998. Proceedings. 8th International Conference On

Date 14-16 Oct. 1998

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  • 8th International Conference on Harmonics and Quality of Power Proceedings Volume II [front matter]

    Publication Year: 1998 , Page(s): i - xii
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    Freely Available from IEEE
  • Author's index

    Publication Year: 1998 , Page(s): 1223 - 1227
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    Freely Available from IEEE
  • Statistical Analysis of the Measured Harmonic Disturbances on the Ac Side of a Metrorail Supply System

    Publication Year: 1998 , Page(s): 1229 - 1234
    Cited by:  Papers (1)
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  • Comprehensive switching functions approach to calculate harmonics produced by multipulse thyristor converters operating under unbalanced supply

    Publication Year: 1998 , Page(s): 837 - 843 vol.2
    Cited by:  Papers (9)
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    This paper describes how a comprehensive switching functions approach can be used to calculate both AC and DC harmonics produced by multipulse thyristor converters operating under nonideal supply conditions. Calculations include unbalanced voltage supply, asymmetric commutating impedances and phase-shift imbalances between transformers. The proposed approach enables easy incorporation of both the zero crossing and the equally spaced firing pulse methods. The validity of the proposed approach is demonstrated by comparison with the results of time domain simulation View full abstract»

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  • The analysis of harmonic generation of SVC and STATCOM by EMTDC/PSCAD simulations

    Publication Year: 1998 , Page(s): 853 - 858 vol.2
    Cited by:  Papers (3)
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    In the paper, the harmonic generation of the conventional SVC and modern STATCOM systems is analysed. At the beginning, short description of the SVC and STATCOM systems is given. Then assumed models of a power system, the SVC and STATCOM systems are described. After scope of the investigations is given, results of harmonic analyses are presented. The SVC and STATCOM systems have been modelled using PSCAD/EMTDC program. During the simulation process, the voltage total harmonic distortion has been calculated. Also one has analysed individually higher harmonics of examined voltage. Different parameters and conditions of operation of simulated systems have been taken into account. At the end of the paper, conclusions from investigations are drawn View full abstract»

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  • Utilisation of static circuit breakers in loop distribution systems for reliability improvement

    Publication Year: 1998 , Page(s): 982 - 987 vol.2
    Cited by:  Papers (1)
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    Nowadays, electric utility companies are expected to provide their customers with a level of quality and reliability higher than that in the past. To improve service on medium voltage (MV) and low voltage (LV) distribution networks, the electric utilities ought to employ new electronic and information technologies, which are quite widespread in industrial plants but not used as much in electric utilities due to the high ratio between costs and benefits. In this work, an optimised management of looped distribution system with solid-state current limiting circuit breakers and distribution automation control is studied, emphasising the possibility of increasing the reliability of the system. First an innovative management of the looped distribution system is proposed; then a comparison in terms of reliability and customer interruption costs among different system configurations with traditional and innovative devices is carried on. In conclusion, the paper highlights the opportunity of accounting for customer marginal benefits as a factor for effective power system planning, design and operation, especially when innovative technologies are adopted View full abstract»

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  • Assessment of power interruption costs for the industrial customers in Greece

    Publication Year: 1998 , Page(s): 761 - 766 vol.2
    Cited by:  Papers (3)
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    Two important economical aspects associated with justifying new facilities, quality and reliability of the electrical power systems are the costs and worth of reliability. The key indicators of this worth are the customer interruption costs which are best and most definitely derived from estimates of perceived costs and losses due to interruptions in their electrical power supply. The customer surveys are mainly utilized to determine these interruption costs. Such a customer survey approach was conducted by the Power Systems Laboratory of the National Technical University of Athens in order to assess the interruption cost for all the different sectors of power customers in Greece. The paper presents the results that were obtained from the survey in the industrial sector during 1997. These results mainly include the interruption cost data and their variation according to the various characteristics of the interruption events and the power supply customers together with a comparison with the respective data published for other countries View full abstract»

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  • Influence of PWM-type voltage waveforms on reliability of machine insulation system

    Publication Year: 1998 , Page(s): 994 - 998 vol.2
    Cited by:  Papers (4)
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    This paper presents the results of life tests performed on models of turn insulating materials of AC rotating machines, having the purpose to infer the aging acceleration effects due to distorted voltage waveforms. PWM speed drives, indeed, have been shown to affect considerably the reliability of AC motors, due to the unusual voltage waveforms supplied to them. These waveforms are significantly different, regarding harmonic content, with respect to those generally considered as the reference for insulation design. The results discussed in this paper show that the main factor affecting insulation aging acceleration is the increase of peak supply voltage, due to wave reflection caused by impedance mismatch of drive and motor, which is applied to turn insulation. Of course, commutation frequency plays also a fundamental role, while less evident is the contribution of rise and fall rate of supply-voltage pulses. A life model is proposed, based on a statistical analysis of life data, which allows evaluation of the degradation acceleration factor View full abstract»

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  • Power flows in distorted electromagnetic fields

    Publication Year: 1998 , Page(s): 678 - 684 vol.2
    Cited by:  Papers (2)
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    The distorted electromagnetic fields are defined as periodic or almost periodic time-varying fields in which a fundamental harmonic exists. They can be represented as sums or series of harmonics or quasi harmonics. Each harmonic or quasi harmonic component of the field is governed by Maxwell's equations and satisfies Pointyng's theorem. Then for each harmonic or quasi harmonic balance, equations of the active and reactive powers are satisfied. Accordingly, for each of them, the power flows can be emphasized. Some new definitions are proposed. The general theory is emphasized by the power flows analysis in a coil with a nonlinear ferromagnetic core with losses View full abstract»

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  • Electronic based equipment for flicker mitigation

    Publication Year: 1998 , Page(s): 1182 - 1187 vol.2
    Cited by:  Papers (5)
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    In this paper, two new approaches for arc furnace flicker mitigation are presented: the unified power flow controller (UPFC) and the series superconducting magnetic energy storage (SMES). These power electronic devices are more expensive than passive or classical equipment of the same rating, but present a better rating versus efficiency. An arc furnace induces different kinds of disturbances during the melting of scraps. Reactive compensation is needed to improve the efficiency of process and to mitigate the disturbances caused to the network. This paper presents different kinds of compensation: active and reactive by shunt and series compensation. It shows how the UPFC or the series SMES can be optimized to take care of all disturbances. The compensation of an AC furnace by these electronics equipment based on an EMTP model are investigated. Finally the paper presents the basic design and control of the series SMES and the UPFC and the comparison between these two structures in terms of rating and flicker mitigation for a real 100 MVA arc furnace View full abstract»

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  • The control of harmonic distortion on an EHV system by the use of capacitive damping networks

    Publication Year: 1998 , Page(s): 706 - 711 vol.2
    Cited by:  Papers (3)
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    The privatisation of the United Kingdom electricity supply system has created conditions in which the pattern of reactive power flow can change rapidly. In order to respond quickly to such changes and maintain security and quality standards the need for additional switched compensation which can be easily re-located has been identified. This paper considers the requirements for large mechanically switched capacitor (MSC) banks on the UK EHV (400 and 275 kV) systems which will not produce any significant magnification of pre-existing harmonic distortion. Results of measurements on the EHV systems have shown an upward trend in distortion levels particularly at 3rd, 5th and 7th harmonics. The paper describes the need to design the MSC as a damped harmonic filter and the choice of a C-type configuration to limit losses. Details of the equipment ratings, in the presence of high levels of pre-existing distortion, and the equipment testing procedures are described View full abstract»

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  • A model for fluorescent lamp flicker in the presence of voltage distortion

    Publication Year: 1998 , Page(s): 1206 - 1210 vol.2
    Cited by:  Papers (3)
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    This paper investigates the luminous flicker phenomenon in fluorescent lamps in the presence of inter or subharmonics affecting the voltage supply. A new analytical, as well as, numerical model is proposed to describe the relationship between luminous flux and voltage interharmonics, stating from the modulation mechanism of the voltage drop on the fluorescent tube. Experimental tests were carried out and the results support the validity of the model View full abstract»

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  • Analysis of interharmonics in DC arc furnace installations

    Publication Year: 1998 , Page(s): 1092 - 1099 vol.2
    Cited by:  Papers (9)
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    This paper deals with interharmonic disturbances encountered during the operation of a DC arc furnace installation. The main cause of the flicker-like disturbances has been identified in a strong harmonic interaction between AC and DC sides of the thyristor converters. In order to analyze the effects of the various system parameters, the frequency response of the entire system has been derived. This approach allows the analysis of the harmonic amplification taking into account the line impedance, resonances introduced by harmonic filters, current regulator parameters, and the synchronizing procedure. Based on this analysis suitable provisions have been taken to mitigate the 125 Hz voltage distortion on a 50 Hz system. The frequency domain analysis has been verified by a time domain EMTP model of the system. Finally, measurements has been taken on the DC arc furnace installation using different control and filter parameters, which show the effectiveness of the adopted provisions View full abstract»

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  • Controlling harmonics from nonlinear loads in commercial facilities

    Publication Year: 1998 , Page(s): 872 - 877 vol.2
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    Nonlinear loads are becoming a larger percentage of the total load in commercial facilities. Fluorescent lighting has always resulted in some harmonic generation. Now, single phase power electronic loads are a major portion of the load in many commercial facilities. They have become a problem for neutral conductors, transformer heating, and interference with other loads on the facility. Besides, single phase electronic equipment, many adjustable speed drives are now commonly applied for HVAC equipment. UPS equipment can have similar characteristics to the ASDs. The combination of these different nonlinear loads can also result in excessive injection of harmonic components from the customer facility onto the utility power system. Harmonic problems can be solved by controlling the harmonics in the loads themselves, through filtering (active or passive) on the electrical system, or by rating the system components to handle the harmonic levels. This paper discusses the expected harmonic levels in a facility as a function of the amount of nonlinear load of the different types. Alternatives for reducing harmonic distortion levels are discussed View full abstract»

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  • Noncharacteristic line harmonics of AC/DC converters with high DC current ripple

    Publication Year: 1998 , Page(s): 755 - 760 vol.2
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    To investigate the basic mechanisms generating noncharacteristic line current harmonics of AC/DC converters with high DC ripple, the assumption of negligible small commutation is used. Thus, simple analytical models can be derived describing the effect of voltage unbalance in case of equidistant phase angle control and control angle asymmetry, respectively. By means of superposition of both components, the according behaviour applying individual phase angle control is described. Finally, it is shown that the effect of resonance excitation in diode rectifier circuits can also be estimated using the proposed modeling. Comparing simulations confirm the validity of the approximations. However, the strong influence of the commutation especially on the negative sequent systems requires further investigations View full abstract»

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  • An adaptive Kalman filter for dynamic estimation of harmonic signals

    Publication Year: 1998 , Page(s): 636 - 640 vol.2
    Cited by:  Papers (18)
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    In electrical railway systems there is often a need of detecting or/and predicting harmonic signals contained in measurement data for vehicle control or monitoring purpose. An efficient on-line estimation method for such applications is the Kalman filter technique. However, the performance of a standard recursive Kalman algorithm is strongly dependent on the a priori information of the process and measurement noise which is either unknown or is known only approximately in practical situations. Furthermore, a Kalman filter often suffers from the problem of “dropping off” and loses then the ability to match abrupt parameter changes. In this paper an adaptive Kalman filter based on correlation analysis is proposed to help overcome these problems. The modelling and estimation technique is described in the paper. Simulation results using measured vehicle line current demonstrate the effectiveness of the proposed method View full abstract»

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  • Modelling, analysis and control of unified power quality conditioner

    Publication Year: 1998 , Page(s): 1035 - 1040 vol.2
    Cited by:  Papers (8)
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    The power quality improvement of a sensitive load by an unified power quality conditioner (UPQC) is presented. The UPQC, consists of back-to-back connected series and shunt active filters, is modelled using a state-space-averaging technique to analyse its behaviour. The enhancement of shunt active filter performance is achieved by applying a moving time window method. The performance of UPQC under load nonlinearities and source disturbance conditions is investigated using simulation as well as experimental results View full abstract»

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  • Modeling a power transformer for investigation of digital protection schemes

    Publication Year: 1998 , Page(s): 1041 - 1046 vol.2
    Cited by:  Papers (3)
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    A three-phase transformer model for the calculation of electromagnetic transients for differential protection studies is presented. The ATP-EMTP was chosen as a computer tool for modeling the following situations: internal faults; transformer energization and removal of external faults. An application of the methodology is exemplified for a 138/13.8 kV-25 MVA transformer, where some transient results are presented View full abstract»

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  • Evaluation of a shunt active filter using frequency identification

    Publication Year: 1998 , Page(s): 617 - 622 vol.2
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    In general every electrical consumer connected to a power distribution network-be it single-phase, three-phase, AC or DC-should be supplied by a voltage quality that allows him to perform his functions without any disturbances caused by the supplying network. On the other hand the consumer should reduce the system perturbations produced by himself so far that no other consumers or installations are disturbed. This holds true for utility grids as well as for railway power supply. Nowadays consumers connected to utility grids as well as railway power supplies often cause undesired oscillations. The frequencies of these oscillations may be integral multiples of the base frequency (so-called harmonics), but often they are not (so-called interharmonics). If quantities of such loads are to be analysed in the frequency domain, for example to evaluate the advantages and disturbances caused by an active filter, interharmonics cause problems. This paper evaluates a shunt active filter using a frequency identification method, which in many cases solves the analysis problems caused by interharmonics View full abstract»

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  • Impact of wind turbines on voltage quality

    Publication Year: 1998 , Page(s): 1158 - 1161 vol.2
    Cited by:  Papers (7)
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    Operation of wind turbines has an impact on the voltage quality at the connected electric network. The issues of concern are the impact on the magnitude of the voltage, flicker and distortion of the voltage waveform Aiming at securing proper voltage quality and still enable a fair amount of wind power in the electric network, simplified assessment e.g. characterizing wind turbines only by their rated power, may not be appropriate. Rather, this paper introduces a set of parameters characterizing the relevant electric quantities of wind turbines, and applies these to predict the impact of wind turbines on voltage quality. The paper concludes by suggesting that the proposed set of parameters should be specified for wind turbines as part of their technical documentation, and that the assessment methods described in this paper should be applied prior to installing new wind turbines View full abstract»

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  • Harmonics, interharmonics and unbalances of arc furnaces: a new frequency domain approach

    Publication Year: 1998 , Page(s): 1071 - 1078 vol.2
    Cited by:  Papers (4)
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    It is well known the complexity of nonlinear models for simulating the dynamic behavior of arc furnaces. For this reason, previous works are based on time domain solutions. In this paper, a new frequency domain approach for obtaining harmonics, interharmonics and unbalances of arc furnaces is proposed. The model assumes a dynamic and nonlinear u-i characteristic of the electric arc as well as continuous evolution of the arc current. The lowest interharmonic frequency to be represented imposes the duration of the “reference period”. Each reference period consists of “N” elemental cycles. The model is described by general equations where the parameter “N” can take any value. The implementation of these equations in a computer program is straightforward, providing very fast calculations for interharmonic components. Finally, the extension of harmonics power flows to interharmonic frequencies is evaluated View full abstract»

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  • Mathematical simulation of DC arc furnace operation in electric power systems

    Publication Year: 1998 , Page(s): 1086 - 1091 vol.2
    Cited by:  Papers (7)
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    Modern high-power DC electric arc furnaces (DC EAF) are considerable sources of power quality impacts in the electric supply systems. These impacts result from the feeding converters, but particularly also from the electric arc in the DC circuit. For an exact analysis of the DC EAF influence on the electric network, both the converter and the electric arc have to be mathematically modelled. The paper presents the results of onsite measurements at a real high-power DC EAF as well as, based on it, a new mathematical approach of the electrical EAF behaviour View full abstract»

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  • Investigation of conducted emissions produced by a PWM inverter-fed motor drive

    Publication Year: 1998 , Page(s): 1218 - 1221 vol.2
    Cited by:  Papers (4)
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    This paper describes an experimental investigation of conducted noise emission produced by a pulse width modulated (PWM) inverter of low power feeding an induction motor. The investigation carried out for two types of PWM waveform generators, namely the pure sinusoidal PWM generator (MA828-2) and the sinusoidal with superimposed third harmonic PWM generator (MA828-1). Measurement of conducted EMI noise for the EUT (equipment under test) and its compliance with the regulations is presented. Then, low-cost strategies for improvement in EMC performance of the PWM inverter are proposed View full abstract»

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  • Stochastic assessment of power supplied to intermittent loads

    Publication Year: 1998 , Page(s): 1029 - 1034 vol.2
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    This paper presents a direct probabilistic method for network power assessment. The random variations of power drawn by cyclic intermittent loads are often caused by their nondeterministic switching as well as their different operating characteristics. The basic problem is to find the net value of the required power which depends on the number of loads in operation. Consequently, a more realistic information on the power consumption may be obtained by taking into account the time varying conditions of an electrical installation and then assess its power requirement. Predicting the harmonic emission of polluting loads could be another application of the proposed method View full abstract»

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  • Generation of voltage fluctuations in power systems with DC arc furnaces

    Publication Year: 1998 , Page(s): 1100 - 1105 vol.2
    Cited by:  Papers (2)
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    There is an increasing use of high-power DC arc furnaces for scrap melting all over the world. Onsite measurements in several steel plants with these furnaces have shown that flicker relevant voltage fluctuations cannot be prevented. The first reason is the time-varying need of reactive power. Also dynamic compensators like TCRs are often not able to avoid considerable flicker, particularly in cases of small network short-circuit capacities. Another flicker origin is the existence of interharmonics. Together with the converter-characteristic harmonics, these interharmonics may result in difference frequencies in the flicker-relevant range. In the paper, the general interactions are explained and a calculation program is presented for the simulation of the power quality conditions in the electric power supply system View full abstract»

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