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Generation, Transmission and Distribution, IEE Proceedings-

Issue 2 • Date Mar 1995

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Displaying Results 1 - 18 of 18
  • H optimisation-based power system stabiliser design

    Page(s): 179 - 184
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    An H optimal control method is outlined to deal with uncertainties in power system modelling and operation as they affect the design of a power system stabiliser (PSS). The paper focuses on the design process for PSS using a nominal model with an uncertainty description which represents the possible perturbation of a synchronous generator around its normal operating-point. The uncertainties are due to incomplete knowledge of the physical system in the model formulation process and system abnormal operating conditions. The proposed excitation controller enables the power system to remain stable over a wide range of operating conditions View full abstract»

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  • New technique for the accurate location of earth faults on transmission systems

    Page(s): 119 - 127
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    A new technique for the single-ended location of resistive earth faults on power transmission lines is presented. Unlike previous work, the algorithm developed has inherent insensitivity to setting errors in the remote source impedance value. This is an important feature, since the remote source impedance often varies significantly under operational conditions. The paper shows the theoretical development of the algorithm, together with a detailed consideration of the hardware aspects. Results are presented for a standard 400 kV transmission line application study View full abstract»

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  • Experimental investigation of an advanced static VAr compensator

    Page(s): 202 - 210
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    An advanced static VAr compensator (ASVC) employing a three-level inverter is presented. The paper describes the operating principles and construction of a hardware model of this ASVC scheme. The performance of the ASVC is obtained from an experimental study carried out on the laboratory model. The use of the selective harmonic elimination modulation technique (SHEM) to minimise harmonics is explored. Experimental studies have been carried out to determine the effect of the DC-side capacitor on the harmonic performance of the scheme and the open-loop response speed is also evaluated. Finally, the economic feasibility of this scheme is briefly assessed by comparing the ASVC with a conventional thyristor-controlled reactor/fixed-capacitor scheme View full abstract»

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  • Optimal phase angles of booster transformers in HV and EHV in power systems

    Page(s): 185 - 189
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    In addition to connecting networks with different voltage ranges, the coupling transformers in power systems can also regulate the active and reactive power flows. To reach this goal, not only should the boost voltage magnitude be controlled by regulating the tap changer but also its phase angle should be shifted by changing the winding set connection of the booster with respect to the main transformer. In the paper, analysis of the function of this potential control variable (i.e. `boost voltage phase angle') is considered. How to regulate and coordinate this phase angle is discussed, and, from there, how to improve the indices of power system operation. A new computer aided analytical method is developed. Application of this method in a real power system demonstrates that the new control energy strategy can save operational cost as well as power loss without violating the original operational constraints of this power system View full abstract»

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  • Line conditioning system with simple control strategy and fast dynamic response

    Page(s): 128 - 134
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    The performance and dynamic characteristics of a solid-state line conditioning system which simultaneously eliminates line current harmonics and compensates load power factor is presented and analysed. The line conditioning system is implemented with a pulsewidth modulated voltage-source inverter. Power factor compensation is achieved by controlling the magnitude and the phase angle (delta) of the transistorised PWM inverter output voltage. Fast response times are obtained by adjusting the amplitude of the PWM inverter output voltage through a modulation index control. The principal advantage of this scheme is that it can maintain a near unity mains overall power factor without sensing and computing the associated reactive power component. It can also substantially reduce the harmonic content of the line current when the load is nonlinear. A time domain model is derived and used to accurately predict dynamic behaviour, the stability region and to adjust system controllers. The transfer function of the line conditioning system for open-loop and closed-loop operation is derived. Experimental results confirm the operation characteristics obtained by computer simulation and mathematical analyses View full abstract»

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  • Frequency-independent circuit model of earth return effects in transmission systems

    Page(s): 143 - 148
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    The paper presents an alternative method of calculating the impedance correction terms of an overhead transmission line by taking into account the effect of the earth return. A circuit-based model is proposed that is frequency-independent and can provide the linear parameters of the earth return path. To demonstrate the validity of the model, the theoretical current distributions under steady-state and transient conditions are calculated. The results obtained are compared with values derived using Carson's formula and finite-element analysis. The results are in good agreement. The model is simple to implement, has short computational times, and compared with other approaches it provides a straightforward calculation that has direct physical meaning. The model can be easily adapted into any transient analysis program and used to predict the surge characteristics of the system View full abstract»

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  • Fuzzy-set approach to dynamic voltage security assessment

    Page(s): 190 - 194
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    The paper presents a new approach to dynamic voltage security assessment. This method is based on fuzzy-set theory, and is developed by means of an example system. The large-scale nonlinear voltage instability assessment problem is finally reduced to a fuzzy index, of which the sign is used as a classifier. The preliminary results show that this method can provide high accuracy, and is promising for on-line use because of its fast nature View full abstract»

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  • Tracking constrained adaptive power system stabiliser

    Page(s): 149 - 156
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    The paper deals with the critical parameter tracking problem which arises when online identification strategies are used to model the dynamics of the power system. A tracking constrained identification scheme is proposed to achieve a smooth model transition under operation schedule change or disturbances. Based on the identified model, an adaptive PSS is designed by using an improved self-optimising pole shifting control algorithm and tested on a multimachine power system. Behaviour of the adaptive PSS and its coordination ability with other PSSs in the system are discussed and demonstrated View full abstract»

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  • Artificial intelligence-based machine-learning system for thermal generator scheduling

    Page(s): 195 - 201
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    SHAPES, an artificial intelligence-based, machine-learning thermal-generator scheduling system, for the run-up-to-peak period, has been developed as an extension of earlier work on a heuristic-guided depth-first scheduling algorithm. SHAPES incorporates new machine-learning algorithms, capable of automatically acquiring heuristic-search guidance, alleviating the need for heuristics to be manually provided to the original scheduling algorithm. Further enhancements have also been introduced in the new system, through the use of best-first search to explore the problem space instead of depth-first search. The paper reports on the development of SHAPES, and application studies which have been conducted to determine the effectiveness of its learning subsystem in improving search efficiency, as well as the performance of the new system in relation to the original scheduling algorithm View full abstract»

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  • Evaluation of line loss under load unbalance using the complex unbalance factor

    Page(s): 173 - 178
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    The paper introduces simple criteria to evaluate the line loss under load unbalance by using the complex unbalance factor. The definitions of voltage and current unbalance factors have been extended from the conventional real values to the corresponding values. The complex-valued unbalance factor is composed of a magnitude and an argument portion. The magnitude portion is commonly used to evaluate the effects of load unbalance. In contrast, the argument portion is always neglected. The latter is considerable when the system configuration is asymmetrical or the phase load is unbalanced. The conventional approach which considers only the magnitude portion may therefore distort the explanation of the calculated results and lead to incorrect conclusions. The paper explores the effects of the argument portion as well as magnitude portion on line loss. Examples are given to demonstrate the effects of the phase load unbalance and the significance of the argument portion on the line loss View full abstract»

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  • Response of large industrial customers to electricity pricing by voluntary time-of-use in Taiwan

    Page(s): 157 - 166
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    The paper examines the response to a voluntary time-of-use (TOU) tariff structure by customers in five selected industrial categories in Taiwan. A transcendental logarithmic electricity cost function was selected in this paper to estimate the price elasticity in five selected industries by the econometric method. The model shows that the price elasticity is a function of electricity cost share. The analysis for the selected industries shows that electricity consumption by TOU was highly responsive to price changes. Electricity usages in different time periods were found to be substitutes for most of the industries. The comparison of load patterns of TOU rates with the hypothetical load patterns corresponding to equivalent uniform rate (EUR) structure indicates that the TOU customers decrease peak electricity use and increase off-peak electricity use significantly under TOU tariffs. The analysis of welfare changes between the TOU and EUR structures shows that large social benefits can be obtained from load management by indirect control of loads via a TOU rate structure. Generally, the magnitude of welfare gain closely depends on the customers' response to TOU schedule. With a drastic reduction in peak period consumption, the social welfare will be significantly increased View full abstract»

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  • Steady state model of the AC/DC convertor in the harmonic domain

    Page(s): 109 - 118
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    A set of equations are developed that describe the six-pulse convertor in the steady-state harmonic domain. The method used is to directly convolve in the harmonic domain the DC voltage in each conduction period, with an appropriate sampling function. This avoids the need to use transfer functions, FFTs, or complicated Fourier transforms. The technique is fast and simple, and is able to model effects that have, until now, been largely ignored (such as the DC ripple effect on commutation duration). Moreover, the equations are suitable for inclusion in a Newton-type solution method, as the partial derivatives are easily obtained View full abstract»

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  • Earth fault currents and potentials distribution in composite systems

    Page(s): 135 - 142
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    A method is proposed for the analysis of the distribution of the earth fault currents and earth electrode potentials in composite power systems. The approach suggested extends the application of the method of symmetrical components allowing exact representation of system elements including earth electrodes and bonds effects. Transmission lines and other system elements are modelled using compact multiport representation which is appropriate for a successive interactive calculation with low computer memory requirements View full abstract»

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  • Object-oriented design of trouble call analysis system on personal computer

    Page(s): 167 - 172
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    The paper presents an implementation of a trouble call analysis and service restoration assistance system based on object-oriented techniques. The system utilises various data from the distribution system, the dispatchers' past experience, and employs the graphical display capabilities of a personal computer to provide helpful aid to the dispatchers during the service restoration process. The system data are organised in an object-oriented structure, providing better flexibility for implementing various functions as well as for future expansion and maintenance. The key functions performed by the system and the associated implementation approach are presented View full abstract»

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  • Network modelling of traction substation transformers for studying unbalance effects

    Page(s): 103 - 108
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    The paper presents network mathematical models of traction substation transformers for simulation of the unbalance effects, due to railway demands, on the power supply system. The admittance models consider winding connections and phase-angle displacement between primary and secondary voltage. The proposed models are presented for the single-phase, V- and Scott connections of transformers used in, among other places, high-speed railway stations View full abstract»

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  • Novel approach to alternator field winding interturn fault detection

    Page(s): 97 - 102
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    The paper demonstrates how artificial neural networks can be used for the online detection of interturn faults on the rotor of an alternator. A simple network has been designed and tested on a laboratory micromachine. The tests have shown that by employing a neural network to predict the field current from measurements at the stator terminals, operation with a faulted rotor can be successfully identified View full abstract»

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  • Naturally commutated thyristor-controlled high-pulse VAr compensator

    Page(s): 219 - 224
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    An alternative to the thyristor controlled reactor for use in static VAr compensators is proposed based on the ability of the AC/DC power convertor to absorb controllable reactive power. The standard three-phase bridge configuration is modified, using the concept of DC ripple reinjection, to achieve high pulse operation without the need for passive harmonic filtering. A 36-pulse scaled-down test system is used to verify the theoretical predictions View full abstract»

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  • Anticipatory fuzzy control of power systems

    Page(s): 211 - 218
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    The paper presents an anticipatory fuzzy control scheme to improve the stability of electric power systems. This differs from the traditional fuzzy control in that once the fuzzy-control rules have been used to generate a control value, a predictive routine built into the controller is called for anticipating its effect on the power system output and hence updating the rule base or input-output membership functions in the event of unsatisfactory performance. The effectiveness of the anticipatory and traditional PI fuzzy controllers is demonstrated by simulation studies on a single-machine infinite-bus and multimachine power system subjected to a variety of transient disturbances for different operating conditions. The anticipatory fuzzy control, however, requires a neural network prediction routine using a modified Kalman filter-based fast-learning algorithm View full abstract»

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