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Generation, Transmission and Distribution, IEE Proceedings-

Issue 3 • Date 6 May 2005

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Displaying Results 1 - 18 of 18
  • Coprime factorisation approach in designing multi-input stabiliser for damping electromechanical oscillations in power systems

    Publication Year: 2005 , Page(s): 301 - 308
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    The application of loop shaping in H control design through a dual-input power system stabiliser (PSS) in a benchmark power system model is demonstrated. The PSS stabilises two key system poles contributing to critical electromechanical oscillations involving turbine generators and electrical network. The IEEE First Benchmark Model has been considered in this study to demonstrate the effectiveness of the control. A linearised model of the system is pre- and post-compensated using loop-shaping approach. The problem of robust stabilisation of a normalised coprime factor plant description is formulated into a generalised H problem and the solution is obtained analytically. The performance of the controller shows robustness to electromechanical modes, which were otherwise very poorly damped or undamped depending on operating conditions. The robustness is further validated in Simulink, including nonlinearities and device saturation limits. View full abstract»

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  • Definition and digital algorithms of dielectric loss factor for condition monitoring of high-voltage power equipment with harmonics emphasis

    Publication Year: 2005 , Page(s): 309 - 312
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    Experience and applications of currently available methods for online monitoring and diagnostics of high-voltage power apparatus are briefly reviewed. Based on dielectric physics, a new definition of dielectric loss factor with harmonics emphasis is proposed to evaluate the operational conditions of power apparatus on a more reasonable basis, along with corresponding digitised algorithms. Two approaches, namely the decoupling algorithm and the approximating algorithm, are presented to implement the methodologies with the new definition of dielectric loss factor. The impact of background noise and power-frequency fluctuation on estimation accuracy are analysed by computer simulations, showing better application qualities of the approximating algorithm than the decoupling algorithm. A comprehensive strategy of simultaneous monitoring of sum current, dielectric loss factor, resistive current and capacitive current is recommended to give an effective assessment and diagnosis. View full abstract»

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  • Primal-dual interior-point approach to compute the L1 solution of the state estimation problem

    Publication Year: 2005 , Page(s): 313 - 320
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (182 KB)  

    A solution to the single-snapshot non-linear L1 estimation of the power transmission network is presented. The non-linear L1 estimation problem is formulated as a non-linear program and solved using a primal-dual interior-point approach. The efficiency of this approach is dependent on the numerical procedure used to solve the reduced Karush-Kuhn-Tucker (KKT) system of equations. It is shown that two mathematically equivalent formulations of the non-linear programming problem can be obtained. These formulations lend themselves to fundamentally different numerical procedures to solve the reduced KKT system. Numerical testing on IEEE systems is used to quantify the performance of the interior-point approach on both formulations. Comparisons are also carried out with a recent implementation of an iteratively reweighted least-squares method for non-linear L1 regression. View full abstract»

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  • Direct numerical evaluation of earth return path impedances of underground cables

    Publication Year: 2005 , Page(s): 321 - 327
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    The lossy earth return path influences significantly the impedances of underground power cables, especially in cases where transient simulation models are of interest. The use of approximations for the calculation of the earth correction terms proves to be inaccurate, especially at high frequencies or for low earth resistivities. A novel direct numerical integration scheme for the evaluation of the infinite integral terms is presented. The new method proves to be numerically stable and efficient in all cases examined. Results obtained by the novel integration scheme are compared with those obtained by other approaches, as well as by a finite-element method formulation for several single-core cable configurations and for cases of homogeneous and multilayered earth. View full abstract»

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  • Modelling and simulation of three-phase transformers for inrush current studies

    Publication Year: 2005 , Page(s): 328 - 333
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (345 KB)  

    A fast and stable approach for the simulation of transformer nonlinearities during transient and unbalanced operating conditions is given. The proposed scheme implements separate magnetic and electric equivalent circuits. The solution of the transformer nonlinear mathematical model is carried out using the Newton-Raphson iterative method. Introducing the magnetic circuit nonlinearities into the model as either continuous or piecewise functions eliminated the difficulty of the Jacobian formation. The method was verified against experimental and computed results. The application of the Jacobian iterative method increased the stability and convergence of the solution as compared to a predictor corrector scheme. The proposed method was able to accurately simulate the transformer behaviour under switching and no-load conditions. View full abstract»

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  • Transformer-fault diagnosis by integrating field data and standard codes with training enhancible adaptive probabilistic network

    Publication Year: 2005 , Page(s): 335 - 341
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (422 KB)  

    A transformer-fault diagnosis system (TFDS) using a probabilistic neural network (PNN) and IEC/Cigre standard codes is proposed. Many artificial neural networks (ANNs) have been proposed before, however, the slow repeated iterative process and poor adaptation capability for structural data restrains the ANN applications. An effective and flexible PNN could overcome these drawbacks. In this paper, a PNN analyses the transformer's dissolved gas content to identify faults, while using the gas ratios of the oil and cellulosic decomposition to create training examples. Retraining can be done by adding new examples and new hidden nodes for easy adaptation without doing any computed iteration. The commonly used Excel was integrated to provide a convenient man-machine interface. Computer simulations were conducted with diagnostic gas records, to show the effectiveness of the proposed system. View full abstract»

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  • Approach to determine voltage control areas considering impact of contingencies

    Publication Year: 2005 , Page(s): 342 - 350
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (237 KB)  

    This paper presents an efficient method for the formation of voltage control areas. The proposed method considers the effect of P-V and Q-δ coupling and changes in network topology. The full Newton Raphson load flow (NRLF) Jacobian sensitivities and voltage variations under contingencies have been used for the formation of the voltage control areas. These areas have been reduced to equivalent nodes using the REI reduction technique, and the reduced network has been validated for the voltage stability analysis. The effectiveness of the method has been established on the IEEE 14-bus system and a practical 75-bus Indian system. View full abstract»

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  • Evaluation of lightning surges transferred from medium voltage to low-voltage networks

    Publication Year: 2005 , Page(s): 351 - 356
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (193 KB)  

    The effects of transferred lightning surges on loads connected in long branched low-voltage power distribution networks are evaluated by means of computational simulations. Sensitivity analyses are presented to indicate the role of several parameters in the development of transferred surges. Based on the obtained results, remarks are made regarding load protection. View full abstract»

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  • Energy procurement for large consumers in electricity markets

    Publication Year: 2005 , Page(s): 357 - 364
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (595 KB)  

    The paper considers a large consumer that procures its electric energy in an electricity market, involving both pool and bilateral transactions. Additionally, the consumer operates a self-production facility of limited size. In order to minimise its electricity bill, this consumer should determine the amount of energy bought from bilateral contracts, the quantity of energy purchased from the pool, and the amount of energy self-produced. The novel contribution of this paper is to provide a procedure that allows a large consumer to decide optimally its mix of purchases from different electricity sources. The bilateral contract framework used is flexible enough to accommodate many real-world bilateral electricity agreements. A medium-term decision horizon spanning from one to several months is considered. Results from a realistic case study are presented. View full abstract»

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  • Hybrid filters for power quality improvement

    Publication Year: 2005 , Page(s): 365 - 378
    Cited by:  Papers (51)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (410 KB)  

    Solid-state controllers are widely used to convert AC power for feeding number of electrical loads such as adjustable speed drives, furnaces, power supplies etc. Some of these controllers behave as nonlinear loads because they draw nonsinusoidal current from the AC mains. Filter technology for improving power quality of such loads has matured to a reasonable level. Moreover, hybrid filters are considered one of best options for improving power quality for a number of considerations. A comprehensive review of hybrid filters configurations is given: their control approaches, state of art, design considerations, selection criteria, potential applications, latest trends, future developments and their comparative features. A broad review of the status of hybrid filters to researchers, design and practice engineers dealing with power quality improvements is presented. A classified list of more than 150 research publications on the hybrid filters is also given for quick reference. View full abstract»

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  • Hybrid least-square adaptive bacterial foraging strategy for harmonic estimation

    Publication Year: 2005 , Page(s): 379 - 389
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (377 KB)  

    Harmonic estimation for a signal distorted with additive noise has been an area of interest for researchers in many disciplines of science and engineering. A new algorithm is presented, based on the foraging behaviour of E. coli bacteria in our intestine to estimate the harmonic components present in power systems voltage/current waveforms. The basic foraging strategy is made adaptive, depending on the operating condition, to make the convergence faster. The harmonic estimation is linear in amplitude and nonlinear in phase. As the proposed algorithm does not rely on Newton-like gradient-descent methods, it is used for phase estimation whereas the linear least-square scheme estimates the amplitude, thereby presenting the hybrid method. The improvement in percentage error as well as the processing time compared to the conventional genetic algorithm method is demonstrated. The percentage error in this new algorithm is less than 7% at 0 dB signal-to-noise ratio for Gaussian noise. The performance is quite acceptable even in the presence of decaying DC component as well as changes in amplitude and phase angle of harmonic components. View full abstract»

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  • Technique to evaluate nodal reliability indices and nodal prices of restructured power systems

    Publication Year: 2005 , Page(s): 390 - 396
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (253 KB)  

    Power system restructuring has changed the mechanism of system reliability management and electricity pricing. The electricity price and supply point reliability are correlated due to customer participation in market trading in the new environment. A new technique used to determine both nodal prices and nodal reliability indices of deregulated power systems has been developed based on a probabilistic reliability evaluation approach and optimal power flow method. Customer demand response to price changes in terms of customer interruption cost has been included in the technique to re-dispatch generation and to shed load for releasing network violations caused by contingency states. Instead of using nodal price for the normal operation state, the expected nodal price and the associated standard deviation are used to represent the volatility of nodal price due to random failures. A reliability test system (RBTS) has been analysed to illustrate the technique. View full abstract»

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  • Method for co-ordinating application of FACTS-based stabilisers in multimachine power system using fuzzy output feedback controller

    Publication Year: 2005 , Page(s): 397 - 405
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (730 KB)  

    A new fuzzy proportional action is introduced to enhance the performance of output feedback controllers. This fuzzy system has a simple structure and acts as a nonlinear function so that the gain of the controller is not constant but changes according to the error value. To show the effectiveness of the proposed fuzzy output feedback controller computer simulations for co-ordination application of two thyristor controlled series capacitor-based stabilisers are performed. View full abstract»

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  • Parallel interaction protocol for electromagnetic and electromechanical hybrid simulation

    Publication Year: 2005 , Page(s): 406 - 414
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (291 KB)  

    A new hybrid simulator is presented, which comprises a transient stability (TS) simulator interfaced with an electromagnetic transients (EMT) simulator. It can simulate very large networks with TS simulator-like speed, while delivering EMT simulator-like accuracy on key components, while running in real time or in accelerated time modes. In the accelerated time mode, the simulator can be used as a system operation tool, offering extended contingency lists (such as mal-operation of power electronic devices) for dynamic security assessment. In real-time operation, the simulator can be interfaced with real control system hardware for detailed study, including the effects of waveform distortion and mal-operation of switching devices. Much of the development work in this area has been based on a serial communication protocol whereby each of the two different simulators runs in turn. However, a serial-protocol-based hybrid simulator cannot meet the real-time requirement of continuous operation of the EMT simulator. A parallel protocol is proposed, whereby both simulators run continuously, such that real-time operation is feasible. The feasibility of the proposed hybrid simulator is demonstrated by case studies, which show very good comparison between the parallel and series protocols, as well as with an EMTP benchmark. View full abstract»

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  • Design of adaptive load shedding by artificial neural networks

    Publication Year: 2005 , Page(s): 415 - 421
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (239 KB)  

    The design of an adaptive load-shedding strategy by executing an artificial neural network (ANN) and transient stability analysis for an electric utility system is presented. To prepare the training data set for an ANN, the transient stability analysis of an actual power system has been performed to solve for minimum load shedding with various operation scenarios without causing the tripping problem of generators. The Levenberg-Marquardt algorithm has been adopted and incorporated into the back-propagation learning algorithm for training feedforward neural networks. By selecting the total power generation, total load demand and frequency decay rate as the input neurons of the ANN, the minimum amount of load shedding is determined to maintain the stability of power systems. To demonstrate the effectiveness of the proposed ANN minimum load-shedding scheme, a utility power system has been selected for computer simulation and the amount of load shedding is verified by stability analysis. View full abstract»

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  • Bidding strategy for FTR obligations in transmission markets

    Publication Year: 2005 , Page(s): 422 - 428
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (172 KB)  

    In electricity markets, the financial transmission right (FTR) is an important tool for hedging congestion charges. A risk-constrained FTR bidding model is proposed for transmission auction markets. Based on the forecast differential LMP between sink and source points of certain FTRs, bidders try to maximise their expected pay-offs by taking into account the associated risks. Supposing the forecasted distribution of differential LMPs and bidders' risk preferences are known among all bidders, the problem is modelled as a bilevel optimisation with the upper subproblem representing bidders and the lower subproblem representing the solution to the ISO's FTR market clearing problem for maximising the revenues collected from the FTR auction. The bilevel optimisation problem is solved by developing the sensitivity of a bidder's expected utility with respect to its bidding strategies. A three-bus system with four bidders is considered to illustrate the proposed method. The results show the impact of forecasted differential LMP and bidders' preferred risk level on FTR bidding. View full abstract»

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  • Quantification of damping contribution from loads

    Publication Year: 2005 , Page(s): 429 - 434
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (230 KB)  

    A method to identify the effect of load dynamics on inter-machine oscillations is developed. This contributes to the main aim of finding the sensitivity of the oscillatory modes with respect to the presence of particular loads in a multi-machine power system. In this method the sensitivity is found by using the identified oscillatory frequencies of the inter-machine oscillations, the identified load model, and the right and left modal matrices. Simulation of a test power system, including three generators and nine buses, is used to validate the algorithm. This approach is applied to measurements of the inter-machine oscillations of the Australian network and sensitivity to one particular load is identified. View full abstract»

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  • New technique for frequency and amplitude estimation of power system signals

    Publication Year: 2005 , Page(s): 435 - 440
    Cited by:  Papers (18)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (193 KB)  

    This paper describes the design, analysis and computational aspects of a technique for the measurement of power system voltage, current and frequency. This technique can be used in a digital AVR for the state estimation of turbine-generator terminal quantities or in a digital relay for protection of a power system. This technique provides fast and accurate estimation of power system frequency, and is used in a Kalman-filtering algorithm to estimate power system voltage and current signals. Practical considerations such as the effect of power system harmonics, noise, frequency changes, mechanical and electrical load changes are taken into account during implementation of this technique. Several computer simulation tests are presented to highlight the usefulness of the technique. Simulation results show that the technique can simultaneously estimate the amplitude and frequency of a sinusoidal signal, even in the case that the signal is distorted by harmonics or noise or encounters frequency changes. View full abstract»

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