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IEE Proceedings C (Generation, Transmission and Distribution)

Volume 140, Issue 6, November 1993

Volumes & issues:

Volume 140, Issue 6

November 1993

Dispatch of capacitors on distribution system using dynamic programming
  • Author(s): Y.-Y. Hsu  and  H.-C. Kuo
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 433 –438
  • DOI:  10.1049/ip-c.1993.0063
  • Type: Article
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  • p. 433 –438 (6)
    The dispatch of capacitors on a distribution feeder in daily system operation is investigated. The objective is to reach an optimal capacitor dispatching schedule, based on the forecast hourly loads for the next day, such that the total feeder loss in a day is minimised. The constraints that must be taken into account include the maximum allowable number of switching operations in a day for each capacitor, and the voltage limits on the feeder. An approach based on dynamic programming is presented to reach such an optimal schedule. To demonstrate the effectiveness of the proposed approach, the dispatch of capacitors on a distribution feeder within the service area of Taipei West District Office of Taiwan Power Company is investigated. It is concluded that a greater loss reduction can be achieved by the optimal capacitor dispatch than by the fixed-schedule dispatch.
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Improvement on state formulation, stratification and estimation in Monte Carlo production cost simulation
  • Author(s): S.L. Chen  and  S.R. Huang
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 439 –446
  • DOI:  10.1049/ip-c.1993.0064
  • Type: Article
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  • p. 439 –446 (8)
    A computer algorithm designed for Monte Carlo production cost simulation is described. The design seeks to enhance the precision of production cost estimation at a reduced computation time compared with the existing approach. The algorithm has three major computer steps: (i) to formulate a state population according to the uptime/downtime of the generating unit, hence to simulate generation availability; (ii) to stratify this population by a mathematical rule and draw sample states out of each stratum; and (iii) to estimate the population mean of unit commitment production costs by the rank statistics of the sample. The stratification rule aims to remove any judgemental input and to render the stratification process entirely mechanistic. The estimator, given by rank statistics of the sample, can avoid identification of the regression model and thus save computation time. The algorithm has been evaluated and compared numerically with the existing approach. Hence, the effectiveness on precision improvement is demonstrated.
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Three terminal line protection based on a superimposed component impedance relay
Modelling multiple injection bus in power system state estimation
  • Author(s): C.N. Lu ; R.C. Leou ; C.L. Cheng ; T.S. Rai
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 455 –461
  • DOI:  10.1049/ip-c.1993.0066
  • Type: Article
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  • p. 455 –461 (7)
    State estimation which uses redundant real-time telemetry to estimate the system state is considered to be one of the essential parts of the modern energy management system. Owing to modelling restrictions in a multiple injection bus, many of the injection measurements at a bus, in certain circumstances, are not usable, and the estimated net injection cannot be correctly distributed among the individual injections. Two new methods are proposed to model the multiple injection bus. Test results indicate that the proposed methods cannot only utilise all available measurements but also provide a convenient way of estimating individual injections contributing to a bus.
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Damping torsional oscillations using a SIMO static VAR controller
  • Author(s): S. Lee  and  C.-C. Liu
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 462 –468
  • DOI:  10.1049/ip-c.1993.0067
  • Type: Article
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  • p. 462 –468 (7)
    Stabilising torsional oscillations using a single input multiple output (SIMO) static VAR controller is investigated. An eigenstructure assignment technique is applied to design it. The designed controller can be easily implemented by a multiple proportion integral (MPI) controller using medium pressure turbine speed, two low pressure turbine speeds, and generator shaft speed as the feedback signals. Eigenvalue analyses under a wide range of series capacitor compensations and loading conditions, time domain simulations under a pulsed torque disturbance, and fast Fourier transform (FFT) analyses for system behaviour are all performed to demonstrate the effectiveness of the proposed controller.
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Calculation of harmonics and interharmonics in HVDC schemes with low DC side impedance
  • Author(s): L. Hu  and  R. Yacamini
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 469 –476
  • DOI:  10.1049/ip-c.1993.0068
  • Type: Article
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  • p. 469 –476 (8)
    When HVDC schemes are used to join AC systems of different frequencies, frequencies other than the well known characteristic harmonics are produced in the AC systems, and these are often called interharmonics. This paper examines these interharmonics and shows that, for HVDC schemes with low DC side reactance, another set of interharmonics will exist only on the DC side. These are a function of the impedance of the convertor seen from the DC side. It is shown that this impedance is time varying and, by modulation theory, will produce DC side harmonic frequencies some of which may be at low frequency. It is also shown that the amplitudes of characteristic harmonics and interharmonics will be changed by this effect. The method based upon modulation theory is compared to the results of a time domain computer simulation. The results shown will also be applicable to variable frequency motor drives.
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Constrained frequency domain algorithms for determination of parameters of fundamental sinewave of signals
  • Author(s): K.Fr. Eichhorn ; T. Łobos ; P. Ruczewski
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 477 –480
  • DOI:  10.1049/ip-c.1993.0069
  • Type: Article
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  • p. 477 –480 (4)
    The method presented enables the design digital FIR filters satisfying specific frequency characteristics with auxiliary constraints. Such filters make it possible to estimate in realtime the parameters of fundamental current and voltage waveforms encountered in electrical power systems. The problem of design is converted to an optimisation problem with constraints using the standard least-squares criterion. The minimisation problem using the Lagrange multiplier method is mapped to a simpler problem of solving a set of linear equations. Using this method we optimise the selection of algorithms for particular applications.
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Critical-cluster identification in transient stability studies
  • Author(s): Y. Xue  and  M. Pavella
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 481 –489
  • DOI:  10.1049/ip-c.1993.0070
  • Type: Article
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  • p. 481 –489 (9)
    A method is proposed for identifying the critical cluster of machines, i.e. the machines responsible for loss of synchronism in a power system following a large disturbance. It is based on the conjecture that the loss-of-synchronism condition can be recognised by, first, considering ‘near-critically cleared trajectories’ of the machines and, secondly, observing how they are organised near the system's unstable equilibrium point. The term ‘near-critically cleared trajectories’ is meant to imply the swing curves of the system in the postfault-phase and is computed for a fault-clearing time that is slightly larger than the actual critical clearing time. To realise the above, the method uses the extended equal-area criterion. This direct criterion makes it possible to assess a convenient clearing time for computing the swing curves; to determine the system's unstable equilibrium point with great ease; and to select the critical machines by observing them at the time corresponding to this unstable equilibrium point. It also makes the speed of critical-cluster identification compatible with real-time requirements. Examples are given using the IEEE test system to illustrate the essential features: reliability in correctly identifying the critical clusters, robustness with respect to its capacity to do so under very stringent conditions, and effectiveness concerning its ability automatically to identify critical clusters of any size, i.e. irrespective of the number of machines that they contain.
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Period-doubling route to chaos in an electrical power system
Method for reliability analysis of industrial distribution systems
  • Author(s): M.H.J. Bollen
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 497 –502
  • DOI:  10.1049/ip-c.1993.0072
  • Type: Article
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  • p. 497 –502 (6)
    The method for reliability analysis of industrial distribution systems presented in this paper combines a Monte Carlo simulation with an electrical network model. The Monte Carlo simulation generates fail and restore events in stochastic components. The flexibility of the Monte Carlo simulation made it possible to include ageing of components and preventive maintenance. As industrial loads are often sensitive to short-duration voltage sags, the influence of these sags had to be included in the model. This is done by using the maximum permissible voltage sag at the load nodes as an interruption criterion. The occurrence of a short-circuit and the intervention by the protection are modelled in detail. Mal-trips as well as fail-to-trip of the protection are included. The method presented in this paper is suitable for industrial (and other) distribution systems where sensitive loads are present, where maintenance of components is important and/or where the behaviour of the protection influences the reliability.
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Operating characteristics of unit and group connected generator-HVDC converter schemes
  • Author(s): J. Arrillaga ; J.R. Camacho ; S.J. MacDonald ; C.P. Arnold
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 503 –508
  • DOI:  10.1049/ip-c.1993.0073
  • Type: Article
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  • p. 503 –508 (6)
    The two alternatives for the direct connection of generators to HVDC converters, i.e. the unit and group connections, are compared under varying steady-state operating conditions at nominal operating frequency. Direct connection is defined as the connection of synchronous generators and converters without AC filters and with the transformer having simultaneously the function of converter and step-up transformer. With all the units in service both schemes display the same characteristics. By reducing the number of generators in service the group connection becomes more efficient at lower power levels. The opposite effect occurs with the unit connection where the efficiency reduces with the power levels, particularly with fewer generators in service. Moreover, in the last-mentioned case the inverter end of the link requires extra reactive power compensation. Therefore for schemes operating at varying power levels and fixed frequency the group connection should be the preferred alternative.
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Simulated annealing based economic dispatch algorithm
  • Author(s): K.P. Wong  and  C.C. Fung
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 509 –515
  • DOI:  10.1049/ip-c.1993.0074
  • Type: Article
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  • p. 509 –515 (7)
    This paper develops an economic dispatch algorithm for the determination of the global or near global optimum dispatch solution. The algorithm is based on the simulated annealing technique. In the algorithm, the load balance constraint and the operating limit constraints of the generators are fully accounted for. In the development of the algorithm, transmission losses are first discounted and they are subsequently incorporated in the algorithm through the use of the B-matrix loss formula. The algorithm is demonstrated by its application to a test system. The results determined by the new algorithm are compared to those found by dynamic programming with a zoom feature.
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Linear-programming-based decomposition method for optimal planning of transmission network investments
  • Author(s): V.A. Levi  and  M.S. Ćalović
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 516 –522
  • DOI:  10.1049/ip-c.1993.0075
  • Type: Article
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  • p. 516 –522 (7)
    The paper is devoted to an optimal solution of the investment model within overall transmission network expansion planning. The proposed investment model is defined as the static, minimum-cost linear-programming problem. Adequate rearrangement of this model achieves its decomposition into two interrelated subproblems. The first subproblem deals with the solution of initial power flows encompassing security aspects only, and the second subproblem solves superimposed power flows taking into account the economy of the problem as well. The minimum-load curtailment model is used for the solution of the first subproblem, and the proposed model of linear-programming marginal network is used for the solution of the second subproblem. The proposed investment model is incorporated into the newly developed, very flexible procedure for overall transmission network expansion planning, which enables the application of different expansion planning concepts.
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Discrete mode power system stabilisers
  • Author(s): M.L. Kothari ; J. Nanda ; K. Bhattacharya
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 523 –531
  • DOI:  10.1049/ip-c.1993.0076
  • Type: Article
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  • p. 523 –531 (9)
    The paper presents a comprehensive approach for the design of discrete mode conventional power system stabilisers (PSS) considering a machine infinite bus system, using the ISE technique. Investigations reveal that the sampler and zero order hold (ZOH) need to be modelled for sampling frequencies less than 20 times the Nyquist frequency and that, beyond 20 times the Nyquist frequency, the sampler and ZOH may be neglected from the mathematical model. A comprehensive sensitivity analysis reveals that the discrete mode conventional PSS is quite robust and its nominal optimum parameters need not be reset following ±20% changes in inertia constant H, field open circuit time constant T′d0, line reactance xe, AVR gain KA or loading P and Q from their nominal values.
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Monte Carlo simulation model for multiarea generation system reliability studies
  • Author(s): R. Billinton  and  L. Gan
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 532 –538
  • DOI:  10.1049/ip-c.1993.0077
  • Type: Article
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  • p. 532 –538 (7)
    In a Monte Carlo simulation model and procedure for reliability assessment of multiarea generation systems a chronological simulation scheme is described which is capable of recognising different unit failure and repair distributions, different unit types, load forecast uncertainty and tie-line directional transfer capabilities and capacity distributions. Distributions of reliability indices can be obtained by taking advantage of a wide range of output data provided by the chronological Monte Carlo method. The proposed method is illustrated with simulation results based on two multiarea configurations created by connecting several IEEE Reliability Test Systems together. The results show that the proposed model can be an effective tool in multi-area generating system adequacy evaluation.
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Application of Newton optimal power flow to assessment of VAR control sequences on voltage security: case studies for a practical power system
  • Author(s): Y.-Y. Hong ; C.-M. Liao ; T.-G. Lu
  • Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 6, p. 539 –544
  • DOI:  10.1049/ip-c.1993.0078
  • Type: Article
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  • p. 539 –544 (6)
    The application of the Newton optimal power flow (OPF) approach to the assessment of VAR controllers on voltage security in the Taiwan Power Company (TPC) is presented in the paper. Important functions in the developed OPF package were achieved to satisfy dispatching requirements. Cases were studied through use of these functions for the purpose of assessing the effect of the various types of VAR controller while considering control sequences. The weakness of traditional OPF packages is pinpointed in that they only obtain an equilibrium solution without the consideration of a proper control sequence. Several significant comments are suggested, on the basis of these results, to set up useful criteria for the security dispatch. A practical 251-busbar system (Taipower) is used to illustrate the test results.
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