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Volume 140
Issue 4
IEE Proceedings C (Generation, Transmission and Distribution)
Volume 140, Issue 4, July 1993
Volumes & issues:
Volume 140, Issue 4
July 1993
Real time modelling of multimachine power systems
- Author(s): T. Berry ; L.A. Dale ; A.R. Daniels ; R.W. Dunn
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 241 –248
- DOI: 10.1049/ip-c.1993.0036
- Type: Article
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An interactive real time power systems transient response simulator has been implement ed on a parallel processor computer. The paper describes the selection of equations used to model the transient behaviour of multimachine power systems together with the numerical techniques suitable for parallel processing. A partitioned solution algorithm has been adopted to allow simultaneous calculation of the machine equations. Key features of the multiple microprocessor computer architecture and associated multitasking operating system are presented. Results from the simulator compare well with those from the test proven CEGB computer program. The present user interface includes animated graphical displays to emulate control room instruments, since immediate applications are in operator training and operational planning exercises. Following the recent development of more powerful hardware, such simulators are capable of modelling large power systems for long term planning studies.
Alleviation of line overloads and voltage violations by corrective rescheduling
- Author(s): P.R. Bijwe ; D.P. Kothari ; L.D. Arya
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 249 –255
- DOI: 10.1049/ip-c.1993.0037
- Type: Article
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p.
249
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This paper presents simple and efficient algorithms for the alleviation of line overloads and voltage violations by corrective rescheduling. The proposed approach utilises the decoupling of real and reactive power and the decomposition between optimisation without security constraints and optimisation to satisfy security constraints. Highlights of the proposed approach are: (i) a choice of performance index which ensures that alleviation of some of the existing violations does not create any fresh violations, thus avoiding the need for cycling in optimisation and, (ii) the use of a classical optimisation technique for faster solutions. Results for two sample test systems have been presented to validate the proposed algorithms.
New tool for reactive power planning
- Author(s): A. Losi ; F. Rossi ; M. Russo ; P. Verde
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 256 –262
- DOI: 10.1049/ip-c.1993.0038
- Type: Article
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256
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A new tool for planning reactive power compensation is presented. It is based on the capability chart of the power system, which describes the domain of allowable operation of the system in the plane of total active and reactive load demand. Reliability concepts are used to describe the ability of the power system to face the load; the stochastic approach is adopted because load demand is fundamentally uncertain. Results for the AEP 14 bus test system are presented.
Design of variable structure power system stabilisers with desired eigenvalues in the sliding mode
- Author(s): M.L. Kothari ; J. Nanda ; K. Bhattacharya
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 263 –268
- DOI: 10.1049/ip-c.1993.0039
- Type: Article
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p.
263
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A systematic approach for the design of variable structure power system stabilisers (VSPSS), with desired eigenvalues in the sliding mode is presented. A detailed sensitivity analysis reveals that the VSPSS is quite robust to wide variations in operating load and system parameters.
Generalised transformer model based on the analysis of its magnetic core circuit
- Author(s): N.D. Hatziargyriou ; J.M. Prousalidis ; B.C. Papadias
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 269 –278
- DOI: 10.1049/ip-c.1993.0040
- Type: Article
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In this paper a new transformer model, named ‘geometrical’, is developed, based on the circuit analysis of its magnetic core. The method is general and can be used for any type of multiphase multiwinding transformer. The model simulates the transformer as a set of coupled branches and can be incorporated into the widely known electromagnetic transients program (EMTP). A basic advantage of the model is that it can represent any asymmetry of the transformer magnetic circuit. As a study case, the model of an actual 280 MVA autotransformer is derived and used for the simulation of various steady state and transient conditions.
Voltage stability: analysis needs, modelling requirement, and modelling adequacy
- Author(s): M.K. Pal
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 279 –286
- DOI: 10.1049/ip-c.1993.0041
- Type: Article
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p.
279
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The importance of representing dynamic loads by valid dynamic models in dynamic analyses of voltage stability is demonstrated. Several dynamic load models reported in the literature are reviewed. It is shown that, for loads with slow dynamics or when the system voltage may be assumed constant, small signal stability is independent of the load model used, provided the model parameter values are correctly chosen. The same results can also be predicted by steady-state analysis by appropriately modifying the conventional power flow model. In large disturbance situations, and when the load dynamics exhibit fast response characteristics, a detailed system modelling is needed. An argument is presented in favour of using the theoretically rigorous and well established models for loads with fast dynamic response, when detailed analyses are warranted.
Flashover arc motion and its effects on spacer-surface damage in gas-insulated systems
- Author(s): K. Tekletsadik and L.C. Campbell
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 287 –292
- DOI: 10.1049/ip-c.1993.0042
- Type: Article
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287
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Breakdown or flashover arcs in gas-insulated systems (GIS) produce a magnetic force which influences the path of the arc and has a decisive effect on the spacer-surface damage experienced during flashovers. An experimental arrangement was developed to study breakdown/ flashover arc dynamics and their effect on spacer-surface damage in an 8 m experimental GIS. A mild-steel flange and aluminium disc piece were made to hold the test epoxy-resin spacer and to have an access to take arc photographs in an open-to-air configuration at the open end of the GIS, with special spacer-electrode arrangements to study the arc lift off and push onto the surface during flashover on both sides of the spacer. The principle of arc dynamics is discussed, along with, experimental arrangements, results obtained from arc photographs and the effects of the arc path on spacer-surface damage.
Optimal coordination of shunt reactors to enhance system performance at light load operation
- Author(s): Z. Elrazaz and A.A. Al-Ohaly
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 293 –298
- DOI: 10.1049/ip-c.1993.0043
- Type: Article
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p.
293
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Large reactive power surplus at light load operation may force system generators to reduce their excitation, and consequently may lead to unstable operation. This Paper proposes an optimal approach, based upon reactive power sensitivities, to locate and assign the reactor ratings for different operating conditions. The approach is utilised to enhance an existing power system performance at light load operation.
Vector analysis and control of advanced static VAR compensators
- Author(s): C. Schauder and H. Mehta
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 299 –306
- DOI: 10.1049/ip-c.1993.0044
- Type: Article
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p.
299
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The advanced static VAR compensator (now widely known as the static condenser or STATCON) uses a high power self-commutating inverter to draw reactive current from a transmission line. Two fundamentally different types of invertor can be used for this purpose; one providing control of output voltage magnitude and phase angle, and the other having only phase angle control. For each of these types, the governing equations are derived, and frequency domain analysis is used to obtain the relevant transfer functions for control system synthesis. Further analysis is provided to determine the response of the STATCON to negative sequence and harmonic voltage components on the transmission line. The results are illustrated with measured wave forms obtained from a scaled analogue model of an 80 MVAR STATCON.
New decomposition for 3-phase currents in power systems
- Author(s): J.L. Willems and D. Aeyels
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 307 –310
- DOI: 10.1049/ip-c.1993.0045
- Type: Article
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307
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A new decomposition of sinusoidal 3-phase currents is proposed. The main feature is that it leads to the compensation of nonactive currents partly by elements without energy storage and partly by means of linear elements with energy storage (inductors and capacitors). The proposed decomposition is compared with existing procedures, such as those developed by Akagi-Nabae and by Czarnecki.
Unsupervised/supervised learning concept for 24-hour load forecasting
- Author(s): M. Djukanovic ; B. Babic ; D.J. Sobajic ; Y.-H. Pao
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 311 –318
- DOI: 10.1049/ip-c.1993.0046
- Type: Article
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p.
311
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An application of artificial neural networks in short-term load forecasting is described. An algorithm using an unsupervised/supervised learning concept and historical relationship between the load and temperature for a given season, day type and hour of the day to forecast hourly electric load with a lead time of 24 hours is proposed. An additional approach using functional link net, temperature variables, average load and last one-hour load of previous day is introduced and compared with the ANN model with one hidden layer load forecast. In spite of limited available weather variables (maximum, minimum and average temperature for the day) quite acceptable results have been achieved. The 24-hour-ahead forecast errors (absolute average) ranged from 2.78% for Saturdays and 3.12% for working days to 3.54% for Sundays.
Estimation of equivalent models for emergency state control of interconnected power-systems based on multistage recursive least-squares identification
- Author(s): X.-Y. Li and O.P. Malik
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 319 –325
- DOI: 10.1049/ip-c.1993.0047
- Type: Article
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p.
319
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Multistage recursive least-squares (MRLS) identification of the equivalent two-machine model of interconnected electric power systems in emergency state is presented in the paper. Requiring only locally measured variables, the MRLS identification allows the estimation of the reactance of intertie and the parameters of the equivalent two-machine model, including inertia constant, damping coefficient, internal voltage, relative rotor angle and relative speed. In other words, on-line estimation of the equilibrium point and the system states of interconnected electric power systems in emergency state is possible. The estimated model can be utilised in various emergency control strategies or other application. Studies demonstrate the effectiveness of the MRLS identification technique.
Analytical algorithm for constraint relaxation in LP-based optimal power flow
- Author(s): S. Zhang and M.R. Irving
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 326 –330
- DOI: 10.1049/ip-c.1993.0048
- Type: Article
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326
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A new algorithm for constraint relaxation to deal with infeasible problems in LP-based optimal power flow is presented, together with results from tests of the algorithm. This alsorithm follows an analytical approach. In contrast with the traditional iterative methods, the new approach can spread the violations more evenly among all the bottleneck constraints. The computational requirements of the proposed algorithm are modest, and the number of LP iterations in the infeasible case is greatly reduced, enabling constraint relaxation to be applied for all constraints with the ability to use different engineering weightings or priorities.
Phase-shifting transformers in load flow and short-circuit analysis: modelling and control
- Author(s): R.D. Youssef
- Source: IEE Proceedings C (Generation, Transmission and Distribution), Volume 140, Issue 4, p. 331 –336
- DOI: 10.1049/ip-c.1993.0049
- Type: Article
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331
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A new accurate model representing phase-shifting transformers for both load flow and fault analysis is introduced. The model is simple, efficient and numerically stable. The theoretical basis of the model and the practical procedures of implementation for the fast-decoupled load flow method and short-circuit calculation are presented. For load flow implementation the developed model requires no additional storage except for data; the number of iterations and the time per iteration is unchanged. The phase-shifting trans formers have been used for real power control in parallel circuits and the relative analyses and test results are presented. For short-circuit analysis, the asymmetry in the admittance matrix introduced by the phase-shifting transformers is dealt with in two stages. The network is first solved using symmetrical admittance matrix, fully exploiting sparsity, and subsequently the effect of the asymmetry is superposed using the diakoptical approach and effective programming, which optimises the calculation time and storage. To illustrate the process involved a small numerical example is given in Appendix 9.1. The model described was implemented in the Interactive Power System Analysis program [12], and the results of verification for various transformer arrangements in typical practical networks are presented.
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