Online ISSN
1751-8695
Print ISSN
1751-8687
IET Generation, Transmission & Distribution
Volume 2, Issue 4, July 2008
Volumes & issues:
Volume 2, Issue 4
July 2008
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- Author(s): Z. Yining and S. Jiale
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 469 –477
- DOI: 10.1049/iet-gtd:20070494
- Type: Article
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p.
469
–477
(9)
Time-domain compensation of capacitive current, derived from differential equation of Π-equivalent circuit of the transmission line, is introduced into a practical phaselet-based current differential protection scheme. First thoughtful analyses with comparisons are carried out for the time-domain compensation algorithm and also both the phasor compensation method and Bergeron transmission line model method. And then Electromagnetic Transients Program (EMTP) simulations are performed for the three compensation methods mentioned above. The simulation results show that this time-domain compensation method can effectively overcome shortcomings of other two methods, for example, disabling compensation for transient capacitive current, or huge computation consumption and high rate sampling which are far beyond the communication and sampling capabilities that the existing relay devices can offer. As a result phaselet algorithm with 5 ms data window can be applied to current differential protection, hence the trip time is reduced, and the selectivity and sensitivity of protection are enhanced. And also protection devices operating with lower sampling frequency and communication rate present are available for this scheme. - Author(s): P.S. Manoharan ; P.S. Kannan ; S. Baskar ; M.W. Iruthayarajan
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 478 –490
- DOI: 10.1049/iet-gtd:20070423
- Type: Article
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p.
478
–490
(13)
The application and performance comparisons of various evolutionary algorithms (EA) on economic dispatch (ED) problems with non-smooth cost functions considering valve-point effects and multiple fuel options are presented. The EAs such as the real-coded genetic algorithm, particle swarm optimisation (PSO) and differential evolution (DE) are considered. New penalty parameter-less constraint-handling scheme is employed to improve the performance of EA. Ten-generator ED test system is taken for simulation purposes. To determine the efficiency and effectiveness of various EAs, two experiments are conducted, considering only multiple fuel options and considering both valve-point and multiple fuel options. The optimal results obtained using various EAs are compared with Nelder–Mead simplex method and previous reported results. To compare the performances of various EAs, statistical measures such as best, mean, worst, standard deviation and mean computation time over 20 independent runs are taken. The simulation experiments reveal that PSO performs better in terms of solution quality and consistency. DE performs better in terms of mean computation time. For the first time, Karush–Kuhn–Tucker (KKT) conditions are applied to the solutions obtained using EAs to verify optimality. It is found that the obtained results are satisfying the KKT conditions and confirm the optimality. Also, the effectiveness of KKT-based stopping criteria is clearly demonstrated. - Author(s): G.B. Shrestha ; B.K. Pokharel ; T.T. Lie ; S.-E. Fleten
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 491 –504
- DOI: 10.1049/iet-gtd:20070177
- Type: Article
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p.
491
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(14)
Price uncertainty is faced by Gencos in the scheduling of their units in competitive power markets. The proper way to deal with the uncertainty depends on the risk preference of the Genco. Two important means to manage the price uncertainty are (i) suitable flexible bids and (ii) the use of hedging tools such as forward contracts. The influence of these factors in the Genco's short-term generation planning and the corresponding profit performances is studied. The market price is represented by lognormal distribution, Genco risk behaviour is represented by exponential utility functions, the bid functions are taken to be flexible and simple contracts for hedging are assumed available. The unit commitment problem is combined with the hedging problem to obtain the optimal solution. Formulation of the problem to maximise profit in the spot market and its extension to incorporate the risk behaviour of the Gencos and the forward contacts for hedging is presented. Solution method based on genetic algorithms is implemented in MATLAB. It is observed through numerical examples that the flexible outputs and the forward contracts can be used to hedge against price risks to achieve desired profit performance according to Gencos' risk behaviour. - Author(s): H. Samet and M.E.H. Golshan
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 505 –515
- DOI: 10.1049/iet-gtd:20070320
- Type: Article
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p.
505
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(11)
The time-varying nature of electric arc furnace (EAF) gives rise to voltage fluctuations, which produce the effect known as flicker. The ability of a static VAr compensator (SVC), a widely used method for flicker reduction, is limited by delays in reactive power measurements and thyristor ignition. To improve the SVC performance in flicker compensation, a technique for the prediction of EAF reactive power for a half cycle ahead is presented. This technique is based on a new procedure for stochastic modelling of EAF reactive power at an SVC bus. This procedure uses huge field data, collected from eight arc furnaces, to determine the most suitable signal among several candidate signals in view of EAF reactive power prediction. In addition, appropriate orders of autoregressive moving average models are found for reactive power time series. For this purpose, various model adequacy checking methods and some other stochastic analysis methods have been applied on data records. The performance of the compensator in the case of employing predicted fundamental reactive power of an EAF is compared with that of the conventional method by using three new indices that have been defined based on concepts of flicker frequencies and the power spectral density. - Author(s): K.L. Lo and Y.A. Alturki
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 516 –529
- DOI: 10.1049/iet-gtd:20070370
- Type: Article
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516
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Two major contributions are discussed in this part of a two-part set. First, it presents a new concept of market reactive power requirement (Qreq) for every participant in both bilateral and pool markets. This Qreq is defined as the reactive power loss allocation to each bilateral transaction using current adjustment factor (CAF) method that has been proposed in Part 1. When a transaction is allowed to provide reactive power more than its Qreq, it contributes to system reactive power needs and it is considered a reactive power provider. On the other hand, if it cannot produce its Qreq, it relies on other reactive power sources to ship its contracted power and it is considered a reactive power consumer even though it may generate some reactive power. The concept then is extended to participants in a pool market. Secondly, this paper proposes a new general concept of differentiated reactive power requirements for every participant in electricity markets. It assumes that Qreq of a participant depends on its allocated losses using any appropriate loss allocation method. The proposals help system operators and market participants to trade reactive power as well as real power effectively and fairly. The simulation results show validity and consistency of the proposals. - Author(s): M. Soliman ; D. Westwick ; O.P. Malik
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 530 –541
- DOI: 10.1049/iet-gtd:20070405
- Type: Article
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Heffron–Phillips model of a synchronous machine is commonly used in small signal stability analysis and for off-line design of power system stabilisers. The data used to determine the parameters of this model are either hard to measure or require the machine to be taken off-line to take the measurements which, in general, is inconvenient. Identifying these parameters from online data measurements is important since it does not require any a priori knowledge of the machine data. The problem of closed-loop identification of the Heffron–Phillips model parameters is of practical importance since the data used for identification can be gathered when the machine is normally connected to the power system. The use of open-loop identification techniques using data gathered during closed-loop operation of synchronous generators leads to bias errors in the estimated parameters. Motivated by the fact that the synchronous machine model is multivariable and is well defined in a state space structure, a closed-loop subspace parameter identification technique is proposed. Consistency of the proposed approach is illustrated using Monte Carlo analysis. Comparison of the proposed method with open-loop identification technique shows the superiority of this approach. - Author(s): R. Cardoso ; R.F. de Camargo ; H. Pinheiro ; H.A. Gründling
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 542 –555
- DOI: 10.1049/iet-gtd:20070281
- Type: Article
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p.
542
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(14)
Single- and three-phase synchronisation methods based on optimum filtering theory are proposed. These methods are based mainly on the Kalman filter and are therefore termed Kalman filter-phase locked loop. They explicitly include in the problem formulation the presence of harmonics, voltage unbalance, measurement noise, transients and frequency deviation. Such perturbations degrade the performance of many synchronisation structures presented in literature. The formulation presented here makes the synchronisation signals less sensitive to these perturbations. It is also shown that the proposed methods can be helpful by also providing the amplitude, instantaneous phase and frequency of grid voltages that can be useful for the analysis of power quality. Furthermore, the Kalman filter provides a way of obtaining the best compromise between transient response and measurement noise rejection for the synchronisation signals. The paper sets out the development of the proposed methods together with the choice of tuning parameters and their physical meaning. Simulations and experimental results using a DSP TMS320F2812 are presented to show the effectiveness of the proposed schemes. - Author(s): B.K. Panigrahi and V. Ravikumar Pandi
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 556 –565
- DOI: 10.1049/iet-gtd:20070422
- Type: Article
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p.
556
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A novel stochastic optimisation approach to solve constrained economic load dispatch problem using hybrid bacterial foraging (BF) technique is presented. In order to explore the search space for finding the local minima of the current location, the simplex algorithm called Nelder–Mead is used along with BF algorithm. The proposed methodology easily takes care of solving non-convex economic dispatch problems along with different constraints such as transmission losses, dynamic operation constraints (ramp rate limits) and prohibited zones. Simulations were performed over various standard test systems with different number of generating units and comparisons are performed with other existing relevant approaches. The findings affirmed the robustness and proficiency of proposed methodology over other existing techniques. - Author(s): Y.-Y. Hong and P.-C. Chang-Chian
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 566 –575
- DOI: 10.1049/iet-gtd:20070383
- Type: Article
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Secondary current in a current transformer (CT) will become distorted if the CT becomes saturated because of a large primary current and a DC component. This distorted current may leads to a malfunction in the protective relay because it receives a smaller rms current during the period of the fault occurrence. Therefore detection and correction of the distorted current caused by the saturated CT is essential. The application of wavelet transform used to detect the occurrence time of the fault and identify all saturation periods is described. Two features of the fault current were extracted. Fuzzy-c-means was used to partition all possible currents into nine clusters according to their features. Nine multi-layer feed-forward neural networks (MFNNs) were trained individually with the corresponding smaller fault current data sets to obtain corrected secondary currents at the initial stage. Takagi–Sugeno–Kang fuzzy rules were then used to integrate all the MFNN output currents into the final corrected secondary current. The proposed method was verified by SIMULINK/Visual C and was also implemented in a field programmable gate array (FPGA, Altera Stratix EP1S25F780C5 development board). The test results show the online applicability of the proposed method. - Author(s): S.-S. Lin and S.-C. Horng
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 576 –587
- DOI: 10.1049/iet-gtd:20070446
- Type: Article
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p.
576
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An algorithm, based on ordinal optimisation (OO) and sensitive theories, is presented to solve a class of constrained weight least square problems with continuous and discrete variables. The proposed algorithm can cope with an enormous amount of computational complexity problems and has a high probability of obtaining a good enough solution according to the OO theory. This method has some advantages, such as computational efficiency, numerical stability and the superiority of the good enough solution. The proposed algorithm is explicit, compact and easy to program. Test results demonstrate that the proposed approach is more computational-efficient than other existing approaches for solving constrained-state estimation problems with continuous and discrete variables on the IEEE 30-bus and the IEEE 118-bus systems. - Author(s): E. Pajuelo ; G. Ramakrishna ; M.S. Sachdev
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 588 –599
- DOI: 10.1049/iet-gtd:20070505
- Type: Article
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p.
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A new least squares technique to reduce the impact of the transient response of coupling capacitor voltage transformers (CCVTs) on the performance of distance relays is described. Several factors that affect the frequency and time responses of CCVTs are considered. The effect of the transient response on the phasor-estimates is illustrated. An improved least squares technique, which uses the knowledge of the frequency of the CCVT transients while estimating the phasors, is presented. A case, taken from a set of studies, is included to demonstrate the performance of the proposed approach. The robustness of the method is verified by a CCVT parameter sensitivity study. - Author(s): Q. Yang ; W. Sima ; C. Sun ; K. Wu ; J. Li
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 600 –609
- DOI: 10.1049/iet-gtd:20080006
- Type: Article
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A new model based on the numerical electric field analysis has been developed to predict the flashover voltage of ice-covered HV insulators, under AC voltage. By analysing the electric field and combining the U–I and re-ignition characteristics of the arc, the arc propagation process and the flashover voltage of the ice-covered insulators under AC voltage can be obtained. Moreover, the peak value of the voltage on the residual ice is calculated based on the electric field model, which can avoid the errors caused by the simplified residual ice resistance calculation methods in the mathematical model. The results obtained from the electric field flashover model have been compared with other mathematical and experimental results and got a great agreement. - Author(s): R.-F. Sun ; Y.-H. Song ; Y.-Z. Sun
- Source: IET Generation, Transmission & Distribution, Volume 2, Issue 4, p. 610 –620
- DOI: 10.1049/iet-gtd:20070504
- Type: Article
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p.
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In the environment of the power market, available transfer capability is a measure of transfer capability as the technical and commercial indices. In order to meet the requirement of generation reliability by obtaining the support from interconnected areas, the reserve transfer capability of the transmission lines is defined as capacity benefit margin (CBM). At present, CBM is evaluated and optimised through reliability calculation iteration. According to the influence of reserve capacity (or interface transmission capability, reserve clearing prices), three optimisation models are established based on the multi-area generation reliability exponential analytic model, then the sequential quadratic programming is used to solve the CBM of transmission tie lines with respect to variable reliability levels. Because of the analytic model, reliability is calculated only one time, needs no iteration and the coupling influence between areas is taken into account, the optimal results can be computed faster. Test results on TH-RTS show that this method is precise and effective.
Phaselet-based current differential protection scheme based on transient capacitive current compensation
Penalty parameter-less constraint handling scheme based evolutionary algorithm solutions to economic dispatch
Management of price uncertainty in short-term generation planning
Employing stochastic models for prediction of arc furnace reactive power to improve compensator performance
Towards reactive power markets. Part 2: Differentiated market reactive power requirements
Identification of Heffron–Phillips model parameters for synchronous generators operating in closed loop
Kalman filter based synchronisation methods
Bacterial foraging optimisation: Nelder–Mead hybrid algorithm for economic load dispatch
Detection and correction of distorted current transformer current using wavelet transform and artificial intelligence
Algorithm for a class of constrained weight least square problems and applications
Phasor estimation technique to reduce the impact of coupling capacitor voltage transformer transients
A new AC flashover model of ice-covered HV insulators based on numerical electric field analysis
Capacity benefit margin assessment based on multi-area generation reliability exponential analytic model
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