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Volume 149
Issue 2
IEE Proceedings - Generation, Transmission and Distribution
Volume 149, Issue 2, March 2002
Volumes & issues:
Volume 149, Issue 2
March 2002
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- Author(s): F.J. Marín ; F. García-Lagos ; G. Joya ; F. Sandoval
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 121 –125
- DOI: 10.1049/ip-gtd:20020224
- Type: Article
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121
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A global model is presented for short-term electric load forecasting using artificial neural networks. The model predicts the complete curve of the 24 hourly values for the next day. The development of this model consists of three phases: a prior one, in which, starting from historical data, each day is classified according to its load profile by means of self-organising feature maps; the second consists of building and training the neural networks for each class; and the third is an on-line operation phase, in which the prediction is carried out by previously trained recurrent neural networks. The historical data correspond to the central Spanish area from 1989 to 1999. Extensive testing shows that this method has better forecasting accuracy and robustness than statistical techniques, and a greater ability to adapt to different meteorological and social environments than other neural methods. The results obtained in testing are found to be very accurate. - Author(s): K. Pandiaraj ; B. Fox ; D.J. Morrow ; S. Persaud ; J.P. Martin
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 126 –132
- DOI: 10.1049/ip-gtd:20020277
- Type: Article
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126
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Diesel generator sets (gen-sets) have traditionally been used for stand-by power generation. They are now often required to operate in parallel with the utility (peak shaving) or alone (peak lopping) to meet the peak demand at the consumer site. These peak shaving/lopping operations can reduce the system peak demand. As these operations are carried out only for a few hundred hours in a year, the gen-set capacity is unused during the remaining periods of the year. Developments in microcomputers and communication technology have enabled the customer-owned gen-sets to be remotely monitored and controlled from a central location. The central control of MW-size gen-sets can enhance their use in supporting the utility generation at critical times. It will be shown that central control provides an opportunity for more effective peak shaving. The paper also investigates the use of diesel gen-sets as stand-by reserve for isolated systems and presents a demonstration of central control in which a 100-kVA diesel gen-set is operated from a utility control centre. - Author(s): D.H.M. Nguyen and K.P. Wong
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 133 –138
- DOI: 10.1049/ip-gtd:20020215
- Type: Article
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133
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This paper presents a new solution method for the Cournot game equilibrium analysis. The new method allows arbitrary differentiable cost and demand characteristics to be implemented. The solution does not rely on conjectures about market participants' behaviour. The approach taken transforms the search for the Cournot game equilibrium to a problem of under-constrained, multivariate non-linear optimisation. Genetic algorithm techniques were adapted to numerically solve the optimisation for various power markets. Single-consumer power markets are examined and discussed. A new exponential-integral demand function capable of realistically modelling volume-specific inelastic demand is presented. Methods of applying the new approach to assess current market operations and future restructuring options are presented. - Author(s): R.A. Jabr
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 139 –144
- DOI: 10.1049/ip-gtd:20020281
- Type: Article
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139
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The paper presents a cutting-plane algorithm for the solution of a security-constrained economic dispatching problem using a homogeneous interior-point (HIP) method previously presented by the author. The HIP method is shown to be well suited for security dispatch as it accounts for network losses and allows reliable detection of infeasible cases. Inclusion of both (N−1) and (N−2) security constraints is achieved via the cutting-plane algorithm. It is shown that this algorithm is superior to the full approach in both time and storage. Computational results show that it is possible to solve dispatching problems with more than one million security constraints on a standard PC in a moderate amount of time. - Author(s): W.P. Luan ; M.R. Irving ; J.S. Daniel
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 145 –151
- DOI: 10.1049/ip-gtd:20020095
- Type: Article
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145
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A genetic algorithm (GA) is employed to search for the optimal supply restoration strategy in distribution networks. An ‘integer permutation’ encoding scheme is adopted in which each chromosome is a list of indices of switches. The status of each of these switches is decided according to graph theory subject to the radiality constraint of the distribution networks. Each chromosome then maps to a feasible network topology. A special gene ‘0’ is also introduced into the chromosome. Instead of representing a switch, this is a flag that keeps some parts of the network disconnected enabling the GA to find the optimal load shedding strategy where necessary. The proposed algorithm has been tested on a practical system and shown to find an optimal postfault supply restoration strategy, and also the optimal load shedding point when total demand cannot be supplied. - Author(s): T.D.H. Cau and R.J. Kaye
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 152 –156
- DOI: 10.1049/ip-gtd:20020120
- Type: Article
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152
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An evolutionary method is proposed for minimising the operational cost in the scheduling of hydrothermal systems with multiple storage. The method combines the advantages of constructive dynamic programming and evolutionary programming. Instead of evolving the primal variables such as water releases and thermal generator outputs, it evolves the piecewise linear convex cost-to-go functions (i.e. the water value curves). The multistage problem of hydrothermal scheduling is thus decomposed into many smaller one-stage subproblems with evolved cost-to-go functions. For each evolutionary individual, linear programming is used in the forward pass process to solve the dispatch subproblems and the total system operational cost over the scheduling period is assigned to its fitness. Case studies demonstrate that the proposed method is robust and efficient for large complex hydrothermal system with cascaded and pumped storages. - Author(s): J. Ma ; Y.H. Song ; Q. Lu ; S. Mei
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 157 –164
- DOI: 10.1049/ip-gtd:20020074
- Type: Article
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157
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Congestion management is one of the key functions of any independent system operator (ISO) in the restructured power industry. Improper implementation of congestion management will sabotage the security and reliability of the power system, and the free trading in the markets. Based on a hybrid market structure, this paper presents a new framework for dynamic congestion management when system stability is seriously infringed due to unexpected contingencies. An integrated dynamic congestion management market is proposed, in which all market participants are encouraged to participate by submitting their offers and bids for their owned control means. By optimally utilising the available resources in this market, a system operator can stabilise the postcontingency system in an economical way. A modified Quasi-Newton Method is employed to solve the formulated dynamic optimisation problem. The IEEE 30-bus test system is studied to illustrate the proposed method. - Author(s): L.C. Araújo Ferreira ; A.C. Zambroni de Souza ; S. Granville ; J.W. Marangon Lima
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 165 –170
- DOI: 10.1049/ip-gtd:20020016
- Type: Article
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165
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This paper deals with control action to avoid voltage-collapse problems and reduce system loss. First, an optimisation technique based on interior points is used to improve the system-operating conditions. For this purpose, only the voltage controls already available in the system are considered. Secondly, a tangent vector-based technique is used for voltage-collapse analysis and loss sensitivity studies. The optimisation technique is employed in order to quantify the actions qualitatively indicated by the tangent vector. In this case, local shunt compensation is considered. The effects of the system loss and load-margin variation are analysed for each case, and earning opportunities are included based on the new competitive environment. Tests are carried out using the interconnected Southeastern Brazilian system, where all the reactive power limits are taken into account. - Author(s): W.L. Fang and H.W. Ngan
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 171 –174
- DOI: 10.1049/ip-gtd:20020126
- Type: Article
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p.
171
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A succinct method for allocation of network losses is proposed. It takes into consideration the influence of both active and reactive power injected into grids from which network losses and its allocation factors due to each user of the network can be computed in an easy to understand manner. Only one assumption, which is widely accepted in the power industry, is used in the proposed method. Case studies show that the allocation rule can easily be used to allocate network losses to all users of the network. The rule meets criteria for being an acceptable allocation rule for the power supply industry. - Author(s): R.B. Prada ; E.G.C. Palomino ; J.O.R. dos Santos ; A. Bianco ; L.A.S. Pilotto
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 175 –181
- DOI: 10.1049/ip-gtd:20020282
- Type: Article
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p.
175
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Network voltage stability is represented by nodal conditions associated with the maximum active and reactive power flow that can be transmitted from generators to loads. An analytical assessment tool is derived, based on a simple but sound mathematical background, modelling a straightforward physical characterisation of the phenomena. Comprehensive and meaningful indices are introduced. They indicate the MVA margin to the maximum, the region of operation, the relative importance among buses, the loading ranking of the buses, the sensitivity to control actions, and a measure of difficult for power transmission. Numerical results are presented for the Itaipu bulk transmission network in the S/SE of Brazil immediately before a voltage stability blackout in April 1997. Computational efficiency is no burden for real time operation including contingency analysis. - Author(s): J.-C. Peng and H. Jiang
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 182 –185
- DOI: 10.1049/ip-gtd:20020094
- Type: Article
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p.
182
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The contributions of individual complex power sources to branch complex losses and flows cannot be found using existing circuit theory. However, the contributions are the basis for supplement charge allocation in a competitive environment. To determine the contributions accurately and unequivocally, active and reactive currents flowing into a branch from a generator are defined. Based on the definitions and concepts of total differential and definite integral, a new method is derived theoretically to determine contributions of individual complex power generations to branch active and reactive losses, and contributions of individual active or reactive generations to branch complex losses. The nonlinear relationship between the complex power components flowing into and out of a branch from a power source is established. The interaction between active and reactive power flows is considered accurately throughout the study. The theory for determining branch complex loss and flow components incurred by individual generators is founded. It lays theoretical foundations for complex power tracing in lossy power networks. - Author(s): J.-C. Peng and H. Jiang
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 186 –190
- DOI: 10.1049/ip-gtd:20020093
- Type: Article
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p.
186
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The complex power flow tracing in primary equivalent circuit of a power network is much more important under electricity market deregulation. It is pointed out that the decomposition tracing methods for active and reactive powers (or real and imaginary currents) are not accurate. To trace complex power flows accurately a general principle is proposed to determine the sequence of the element's equivalent branches in calculation. Then the fundamental theory proposed in Part 1 is applied to the element's equivalent circuits to derive theoretically the nonlinear relationship between element complex loss components and the complex power components flowing into the element from individual generators. The accurate nonlinear relationship between the complex power components flowing into and out of an element from a power source is therefore obtained. A recursive algorithm is given to find accurately the contributions of individual complex power sources to element complex losses and flows and load powers. Since there is no approximation the algorithm is accurate. Starting from power flow solutions, practical power systems and the IEEE 30-bus system are simulated, and finally analysed. - Author(s): J.S. Dhillon ; S.C. Parti ; D.P. Kothari
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 191 –200
- DOI: 10.1049/ip-gtd:20020176
- Type: Article
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p.
191
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In the multiobjective framework, fuzzy decision-making methodology is exploited to decide the generation schedule of a short-range fixed-head hydrothermal problem. The multiobjective problem is formulated considering five objectives: (i) cost, (ii) NOx emission, (iii) SO2 emission, (iv) CO2 emission and (v) variance of generation mismatch with the explicit recognition of statistical uncertainties in the thermal generation cost, NOx, SO2 and CO2 emission curves and power demand, which are random variables. The solution set of such formulated problems is non-inferior due to contradictions among the objectives taken. The weighting method is used to simulate the trade-off relation between the conflicting objectives in the non-inferior domain. Once the trade-off has been obtained, fuzzy set theory helps the system operator to choose the weighting pattern and thus the operating point that maximises the satisfaction of all the objectives. The results are demonstrated on three sample systems. - Author(s): J.A. Sullivan
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 201 –209
- DOI: 10.1049/ip-gtd:20020078
- Type: Article
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p.
201
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Site tests, to measure the voltages on the surface of the ground above a grid for comparison with calculated values, are only of general interest if the ground has uniform resistivity at and below the grid. However, such conditions rarely if ever exist so the only practical alternative way of obtaining general data is to make tests on model grids in a tank where the electrolyte can be maintained at an homogeneous resistivity. A comprehensive series of such tests has been made in which voltages calculated using empirical formulas given in four of the most commonly used standards are compared with model test results and, as the correspondence is unsatisfactory, new empirical formulas have been developed. That identified the need to account for the shape of the grid and the meshes, and the distortion of the voltage contours close to the grid due to the heterogeneous nature of the local ground. New equations more closely agree with test results. A method of taking into account that the grid is not at the ground surface in the calculation of the HOT distance is given. - Author(s): S. Hongtian ; D.Z. Fang ; S. Wennan ; H.F. Wang
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 210 –214
- DOI: 10.1049/ip-gtd:20020177
- Type: Article
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p.
210
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The speed of simulation of power system dynamics has been one of the topics most concerned with on-line security assessment. This paper proposes a new method for forming the constant Jacobian matrix for enhancing the speed of system simulation. By using the constant Jacobian matrix approach in system simulations, both for post-fault and fault-on duration, simulation efficiency is greatly enhanced. Techniques for speeding up the constant Jacobian matrix approach are discussed. Theoretical analysis is presented to demonstrate how the constant Jacobian matrix approach can be extended to a power system with generator controls. Simulation results with the constant Jacobian matrix approach in the 10-generator New England test system and the North China power system are compared with the results obtained by the use of commercial software BPA. - Author(s): G. Ledwich and A. Ghosh
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 215 –224
- DOI: 10.1049/ip-gtd:20020009
- Type: Article
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p.
215
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The topology and control are discussed of a distribution static compensator (DSTATCOM) that can be operated flexibly in the voltage or current control mode. In the voltage control mode, the DSTATCOM can force the voltage of a distribution bus to be balanced sinusoids. In the current control mode, it can cancel distortion caused by the load, such that current drawn by the compensated load is pure balanced sinusoid. Both these objectives are achieved, irrespective of unbalance and harmonic distortions in load currents or source voltages. The chosen DSTATCOM topology includes three single-phase voltage source inverters connected in parallel to a filter-capacitor, which allows the high-frequency component of the current to pass. A switching control scheme is proposed, and its suitability is proved for this problem. The proposed scheme is verified using computer simulation studies. - Author(s): J.G. Mayordomo ; M. Izzeddine ; S. Martínez ; R. Asensi ; A. Gómez Expósito ; W. Xu
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 225 –232
- DOI: 10.1049/ip-gtd:20020125
- Type: Article
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p.
225
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The main objective of this paper is to provide a flexible three-phase power flow formulation to consider the different structures for PQ loads. A set of equations, based on the current injection method are derived. Additional equations for representing PV machines with their reactive power limits are also considered. The resulting set of nonlinear equations presents a compact formulation where only voltages in rectangular co-ordinates of the symmetrical components are treated as unknowns in a full Newton method. The convergence and robustness of this method has been checked in large systems. - Author(s): T.F. Chan and L.L. Lai
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 233 –241
- DOI: 10.1049/ip-gtd:20020003
- Type: Article
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A steady-state analysis of a novel single-phase self-regulated self-excited induction generator (SRSEIG) which employs a three-phase machine with the Steinmetz connection is presented. Inspection equations are formulated and solved using the method of symmetrical components, yielding the relevant performance equations. An optimisation based approach is used for determination of the per-unit frequency and magnetising reactance, from which the generator performance can be evaluated. The advantages of the single-phase SRSEIG include simple circuit configuration, small voltage regulation, good phase balance, and large power output. With a compensation factor of 0.5, perfect phase balance can be achieved in the three-phase machine when it supplies a specific unity-power-factor load. The effect of compensation factor on the machine performance, such as voltage regulation, voltage unbalance factor, power output and efficiency, is investigated in detail. By using a compensation factor of unity, satisfactory generator performance can be obtained for practical lagging-power-factor loads. Experiments performed on a 2.2-kW induction machine confirm the validity of the theoretical analysis and the feasibility of the single-phase SRSEIG for autonomous power system applications which are important to distributed generation. - Author(s): W.D. Yang ; Z. Xu ; Z.X. Han
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 149, Issue 2, p. 242 –248
- DOI: 10.1049/ip-gtd:20020275
- Type: Article
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p.
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A co-ordinated hierarchical control strategy for multi-infeed HVDC systems is presented. The control law of the HVDC system's transfer power can be derived using optimal control theory with the HVDC system being treated as a variable admittance connected at the commutation busbars. A two-level hierarchical control structure is assumed for the rectifier and inverter side AC system, respectively. The control of constituent HVDC subsystems can be better co-ordinated by the consideration of the AC commutation voltage included in the optimised performance index, and the performance of both rectifier and inverter side AC systems is considered.
Global model for short-term load forecasting using artificial neural networks
Centralised control of diesel gen-sets for peak shaving and system support
Natural dynamic equilibrium and multiple equilibria of competitive power markets
Homogeneous cutting-plane method to solve the security-constrained economic dispatching problem
Genetic algorithm for supply restoration and optimal load shedding in power system distribution networks
Evolutionary optimisation method for multistorage hydrothermal scheduling
Novel framework for dynamic congestion management in open power markets
Interior point method applied to voltage collapse problems and system-losses-reduction
Succinct method for allocation of network losses
Voltage stability assessment for real-time operation
Contributions of individual generators to complex power losses and flows–Part 1: fundamental theory
Contributions of individual generators to complex power losses and flows–Part 2: algorithm and simulations
Fuzzy decision-making in stochastic multiobjective short-term hydrothermal scheduling
Evaluation of mesh and touch voltage at substations
Constant Jacobian matrix and its application to fast trajectory simulation of power systems
A flexible DSTATCOM operating in voltage or current control mode
Compact and flexible three-phase power flow based on a full Newton formulation
Steady-state analysis and performance of a single-phase self-regulated self-excited induction generator
Co-ordinated hierarchical control strategy for multi-infeed HVDC systems
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