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Generation, Transmission and Distribution, IEE Proceedings-

Issue 3 • Date May 1997

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Displaying Results 1 - 17 of 17
  • Statistical study for switching processes in compensated UHV transmission systems

    Page(s): 237 - 241
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    A statistical study of switching transients in a power transmission line with series, parallel or hybrid VAr compensation schemes is presented including the frequency dependence of parameters. A switching model is proposed in which the marginal and the cumulative distributions of the overvoltages are computed. The overall standard deviation of transients for different power transmission line lengths at various switching angles is deduced View full abstract»

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  • Kohonen neural network based approach to voltage weak buses/areas identification

    Page(s): 340 - 344
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (580 KB)  

    The paper presents a neural network based method for the identification of power system voltage-weak buses/areas. By using power flow analysis and the singular value decomposition method, a Kohonen neural network is trained to cluster/rank buses in terms of voltage stability. Special emphasis is placed on the selection of input information and analysis of the neural network output results. The generalisation capability of the Kohonen network under various operating conditions has been tested on a number of systems. The results obtained for the IEEE 30-bus test system are very encouraging View full abstract»

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  • Output feedback TCSC controllers to improve damping of meshed multi-machine power systems

    Page(s): 243 - 248
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    Methods for the co-ordinated design of output feedback damping controllers, for thyristor-controlled series compensators (TCSCs) in a meshed power system, are developed in the paper. The locations for installing TCSCs and the co-ordination of TCSC controls are determined by analysing the mode controllability. The analysis of mode observability is used to select the effective output feedback signals local to the TCSC locations. The design of controller gains is divided into two steps. First, initial gains for each controller are calculated according to the coordination determined by the analysis of the mode controllability. These initial gains are then optimised by using linear programming to satisfy the given design criteria. It is shown that, by using this procedure, the desired damping of the critical modes can be achieved without significantly deteriorating the damping of the other modes and the stability of the power system. It is also shown that the prolonged saturation in the TCSC actuators and the adverse interaction among TCSC controllers can be avoided. The proposed controller design methods are validated by a case study View full abstract»

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  • Quadratic sensitivities for power system steady-state control

    Page(s): 317 - 322
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    Sensitivity analysis is employed by a variety of power system steady-state control tools, either purely algorithmic, knowledge-based or hybrid. First-order Taylor series expansion of the power flow equations is commonly used to calculate the necessary amount of control and predict the future state of the power system, if the control were to be implemented online. This paper introduces the concept of quadratic sensitivity as an extension to the established linear sensitivity approach. Multivariate calculus and tensor algebra are used to derive an analytical expression for the three-dimensional matrix of quadratic sensitivities. Quadratic and linear sensitivities are successively used in voltage control scenarios, simulated on the IEEE 30-bus test system. A comparison between the two approaches in terms of accuracy and run-time is performed. The proposed method improves the accuracy of voltage control by roughly one order of magnitude, provided no discontinuity due to generator reactive power limiting occurs. The effects of discontinuities induced by generator reactive power limiting are also investigated. In such instances, the accuracy of voltage control may be improved by a new generator tracking method View full abstract»

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  • Advanced engineered-conditioning genetic approach to power economic dispatch

    Page(s): 285 - 292
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    Computational efficiency and reliability are the major concerns in the application of genetic algorithms (GAS) to practical problems. Effort has been made in two directions to improve the performance of GAs: the investigation of advanced genetic operators and the development of genetic algorithm hybrids. In this paper, an advanced engineered-conditioning genetic algorithm hybrid (AEC-GA) is proposed, which is a combination strategy involving local search algorithms and genetic algorithms. Moreover, several advanced techniques which enhance program efficiency and accuracy, such as elite policy, adaptive mutation prediction, nonlinear fitness mapping and different crossover techniques, are explored. Using power economic dispatch problems as a basis for comparisons, the outcome of the study clearly demonstrates the advantages of the AEC-GA View full abstract»

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  • Selection of installing locations and feedback signals of FACTS-based stabilisers in multimachine power systems by reduced-order modal analysis

    Page(s): 263 - 269
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    A reduced-order method of modal analysis, based on the extended Phillips-Heffron model, is proposed for the selection of installing locations and feedback signals of FACTS-based stabilisers in multimachine power systems. The method proposed is not only as accurate as the conventional method of modal analysis, but also guarantees that the order of all matrices involved in the reduced-order modal analysis is low, being not higher than the number of machines in the power system. Hence, the numerical difficulty of the eigensolution of high-dimensional matrices is successfully avoided and the computational effort is greatly reduced. The method is demonstrated on a sample three-machine power system for the selection of stabilising signal and installing location of a static VAr compensator (SVC) View full abstract»

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  • Bounding method based on generalised real power distribution factors

    Page(s): 249 - 256
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    An efficient bounding method for distribution network contingency screening is presented. It is based on the use of generalised real power distribution factors capable of modelling the effects of single and multiple topological contingencies, also including bus splits and bus joins deriving from circuit breaker operation. The proposed bounding method consists in identifying the main reclosing paths for the incremental power change. Power flow limits are evaluated for the branches belonging to an interest area centred around the contingency location. The interest area is expanded until the amount of power reclosing through not yet examined branches (boundary flow) falls under a preselected threshold value. Distribution factors are used both in branch flow limit checking and in the computation of the boundary flow. Validation of the proposed method was achieved by extensive testing on both the IEEE 118-bus network and actual systems of Italian, European and North American origin View full abstract»

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  • Methodology and computer package for generation rescheduling

    Page(s): 301 - 307
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (808 KB)  

    Generation rescheduling is a cost-effective way to enhance steady-state dynamic security. The paper presents an improved formulation for generation rescheduling and develops an iterative solution procedure. The proposed method can be used to assist operators to eliminate potential steady-state insecurity, dynamic insecurity, or their combination. Steady state security is established by the well known (n-1) criterion which deals with thermal limits of transmission lines. Dynamic security is defined in such a fashion that transient stability of the system is maintained under any of the contingencies which may occur at each end of every transmission line of a power system. An attractive feature of the proposed method is that it is reliable, realistic and easy to understand since dynamic security is checked in the method by an integration procedure. Simulation results of a 36-machine 200-node practical power system are demonstrated View full abstract»

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  • Co-ordination of emergency secondary-voltage control and load shedding to prevent voltage instability

    Page(s): 293 - 300
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    The authors investigate emergency action in terms of secondary-voltage control and the system load shedding for prevention of voltage instability. Two modes of co-ordination of these control methods with corresponding models are proposed, and these are summarised into developed emergency-control algorithms. The emergency actions of the individual controls and of the proposed co-ordinated control modes are then simulated on a real multimachine power system. The results so obtained show the superiority of the proposed co-ordinated controls over a single control action in preventing voltage instability and system breakdown View full abstract»

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  • Capacitor placement in distribution systems using heuristic search strategies

    Page(s): 225 - 230
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    Heuristic search strategies are used to determine the optimum capacitor placement and ratings for distribution systems. In the heuristic approach proposed, a small number of critical nodes, named sensitive nodes, are selected for installing capacitors that optimise the net savings while achieving a large overall loss reduction. This method insures that voltage constraints are met. This heuristic approach is suitable for large distribution systems and can be useful in online implementation. The proposed approach is applied to a test system and the results are compared with other published techniques View full abstract»

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  • Predictive analogue generator excitation controller

    Page(s): 271 - 278
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    A generator excitation control scheme is introduced which is capable of providing good and consistent voltage control performance, despite wide variations in the system operating conditions. The control scheme is organised so that it comprises a main forward loop, based on a standard voltage error signal, as in a conventional AVR, supplemented by an auxiliary loop incorporating direct axis voltage and current signals. The former loop serves to provide the voltage regulation requirements while the latter serves to compensate for the influence of generator load current on dynamic behaviour View full abstract»

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  • New dynamic, branch exchange method for optimal distribution system planning

    Page(s): 333 - 339
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    The optimisation of distribution system expansion planning constitutes a combinatorial problem. The application of accurate methods has been restricted to power systems of small size, while approximate but more effective heuristic methods have been proposed. This paper presents a new, branch exchange method for the optimisation of multiyear distribution system planning. The problem is faced in two steps: first, a set of economical and technically accepted system configurations is constructed; second, the optimal sequence of system configurations, for a multiyear study period, is determined based on the set of economical configurations. The proposed method is fully dynamic, models accurately the economical and technical data and constraints, while all the power system reinforcement and extension alternatives are modelled and optimised. The effectiveness is demonstrated by applications on a 134 node and 177 branch typical distribution system. Load patterns, for two different seasons, are used to model load variations, while the installation or construction of capacitors, voltage regulators, lines and substations is optimised View full abstract»

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  • New approach for power network clustering using a representative model

    Page(s): 279 - 284
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    A new power network model that is suitable for network clustering techniques is presented. The method is based on representing the system buses as modules and the connecting branches as nets. The number of nets connecting each pair of modules is chosen to be a function of either a single electrical property or a normalised combination of several properties of the equivalent branch connecting the pair of buses. A heuristic approach, based on the approximation of the constrained network partitioning problem into a linear transportation problem, is used to cluster the network into S clusters each containing m buses. The use of a linear-time bus interchange algorithm provides the best possible cluster configuration. The solution technique provides complete freedom in choosing the electrical properties of the greatest importance to the clustering application. Consequently, the selectivity of the proposed solution technique in the aspect of choosing the electrical connectivity measure is evident View full abstract»

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  • Voltage stability: significance of load characteristics and current limiters

    Page(s): 257 - 262
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    Voltage stability phenomena using a three-phase power system model are investigated. Measurements show that it is possible to run the system on the lower side of the PV-curve. Stable operation conditions of an induction motor load and a combination of induction motor and resistance load are discussed. The effect of generator current limiters on the system PV-curve is illustrated by measurements. It is shown that the armature current limiter has a more severe effect on voltage stability than does the field current limiter. The load characteristic is important for voltage stability once a current limiter is activated View full abstract»

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  • New concept in fault location for overhead distribution systems using superimposed components

    Page(s): 309 - 316
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    Due to the challenges facing many electric utilities worldwide as a result of deregulation, the demand and importance of accurate fault location in distribution systems has increased, principally to minimise line outages through effecting repairs expeditiously. The paper presents a novel approach to single-ended fault location for overhead distribution systems based on the concept of superimposed voltages and currents. It is clearly shown that the technique, which is interactive in nature, is highly robust to changes in local and remote source capacities and to the presence of load taps View full abstract»

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  • Damping of multimodal oscillations in power systems using variable structure control techniques

    Page(s): 323 - 331
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    Over the last three decades, efforts have been made to improve the dynamic stability of power systems. Various approaches for the design of power system stabilisers (PSSs) for damping out oscillations in power systems have been reported in the literature. Since the power system dynamics are nonlinear, nonlinear control techniques will be more effective for the control of power systems. The paper presents a technique for designing variable structure controllers (VSCs) to damp out multimodal oscillations in a multimachine power system. A novel approach of incorporating nonlinearities in the system operation at the design stage is proposed. The possibility of achieving a robust design using a simple linear model of power systems is shown. The effectiveness of the proposed VSC is demonstrated by a number of studies. Results show that a VSC performs better than a conventional power system stabiliser and both types of controllers on different units in the system co-operate in a positive manner in damping oscillations View full abstract»

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  • Power systems fault diagnosis using Petri nets

    Page(s): 231 - 236
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    A new method of detecting fault locations in power networks is proposed. The diagnostic process uses Petri net models. This can reduce processing time and increase accuracy when compared with the traditional pattern recognition and hypotheses testing methods. The method is more able than previous methods to adapt to changing network configurations. The methodology was tested using the IEEE 118-bus standard test system. Fast and accurate results were obtained. The method is very suitable for online applications View full abstract»

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