摘要:

The paper presents a new technique for identifying the binding inequality constraints for the optimal power flow Newton approach. The technique is free of the need for user intervention, and reduces significantly the computational effort required by other methods. The algorithm is based on an efficient criteria for selecting and enforcing, at each iteration, a minimum number of active inequality constraints, and on obtaining a solution quickly and with less oscillations. The effectiveness of the proposed method is demonstrated by means of two sample systems.

DOI:10.1049/ip-c.1992.0053

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper presents a new methodology for dynamic equivalents. Two alternative linear simulation methods are proposed for the idenification of coherent generators. The measure of coherency for both methods is the angular speed average deviation of generators. The coherent generators are grouped using a clustering algorithm that assures the uniqueness of the composed coherent groups. The REI approach is applied to transfer the generators of each group to a common busbar. The Levenberg-Marquardt method is used for the coherent generator dynamic aggregation. The dynamic equivalents are evaluated in the New England system and in a configuration of the Brazilian South-Southeastern system with 421 busbars, 717 transmission lines/transformers and 40 generators.

DOI:10.1049/ip-c.1992.0054

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A simple, fast and reliable method is proposed in this paper for load flow analysis. The method depends on the technique of reduction and restoration applied to the conventional Gauss-Seidel (G-S) method. Three IEEE well- conditioned systems, namely 14-, 30-, and 57-bus systems [1], and some ill-conditioned systems were studied, and the results obtained by the algorithm, using an ICL 2966 mainframe computer, are presented. The method can handle bus violations with ease and has the desirable features required for online applications.

DOI:10.1049/ip-c.1992.0055

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper describes the development of a new bad-data detection and identification technique for sequential state estimations using Givens orthogonal transformation. In the sequential state estimation, measurements are divided into basic measurements and redundant ones. Basic measurements are processed first, and then redundant ones are processed one at a time. The successive change in the cost quadratic function, denoted by δJ, resulting from the processing of a redundant measurement, follows a Chi-square distribution with one degree of freedom. If there are no gross errors in the measurements processed up to the present point, then δJis free from the contamination of gross errors in the measurements which are waiting to be processed. Furthermore, δJshows the degree of consistency between the present measurement and those processed before. Hence, the bad-data detection by δJtest is performed, after one measurement has been processed, by comparing the value of δJwith a constant obtained from the Chi-square distribution. The new bad-data identification method is based on the fact that despite the existence of a few gross errors, most of the measurements are ‘good’ in the sense that they are corrupted by Gaussian noise only. Thus, by searching for these ‘good’ ones and processing them first, suspect measurements are isolated to the bottom of the measurement list. This is done by successively rotating the order of measurements while they are being processed. The proposed bad-data detection and identification method does not rely on the analysis of measurement residuals. The new bad-data processing technique is tested on an industrial steam turbine system for which a robust and efficient state estimator has been developed. Numerical results for bad-data detection and identification tests are reported.

DOI:10.1049/ip-c.1992.0056

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The capacitive network often used for the calculation of initial voltage distribution along a transformer winding can be in error for steep impulses. As such pulses are produced by partial discharges (PDs) the application of the concept could contribute to inaccuracies in methods developed for the location of PDs in windings. By means of theoretical analyses, together with experimental measurements on several disc-type windings, it has been found that a capacitive ladder network can be a good representation within a certain frequency limit, the latter being related to the particular winding. Terminal measurements, involving both impulse response and sinusoidal voltage methods, and digital filtering techniques, were employed to determine the appropriate frequencies. Results are presented for tests on 66 kV and 132 kV interleaved windings and a conventional 66 kV winding. For the interleaved windings greatly improved accuracies with steep pulses were achieved, compared with normal impulse voltage distribution measurements. An explanation of the differences between the winding characteristics is given through analysis of the behaviour of two hypothetical double-disc coils (interleaved and conventional), allowing for capacitive intercoupling and series inductance. It is concluded that the studies described will assist in the long-term development of more accurate electrical PD location systems.

DOI:10.1049/ip-c.1992.0057

出版商:IEE    

年代:1992

数据来源: IET

摘要:

An analytical model has been developed to help determine the distribution of the magnetic flux density inside the superconducting AC generator. The model takes into account the number, and the geometric structure, of the winding slots and allows the rotor of the superconducting machine to be designed with optimum magnetic field distribution. The results obtained by the model are verified by comparison with results obtained by former models. The new model is also used to study the influence of the field winding geometry on the magnetic flux density distribution. The paper also reviews two-dimensional modelling methods for calculating the magnetic field inside a superconducting AC generator, and highlights some of the problems and opportunities for the application of these methods to magnetic field analysis of superconducting field winding.

DOI:10.1049/ip-c.1992.0058

出版商:IEE    

年代:1992

数据来源: IET

摘要:

This paper presents a new adaptive control approach for power systems. The proposed adaptive control structure is based on hyperstability theory. The control is constructed so that the closed-loop system is hyperstable, guaranteeing the dynamic stability improvement of power systems. The changable gains, generated by a nonlinear function, act as the adaptive mechanism. Compared with MRAC or STAC, the proposed control structure avoids the difficulty of choosing an appropriate reference model and the burden of implementing an online parameter estimator. Simulation results of a numerical example are presented, which show that the controller works well under system parameter changes, variation in operating conditions and with different disturbances.

DOI:10.1049/ip-c.1992.0059

出版商:IEE    

年代:1992

数据来源: IET

摘要:

This paper presents an application of artificial neural networks (ANN) in support of a decision-making process by power system operators directed towards the fast stabilisation of multi-machine systems. The proposed approach considers generator shedding as the most effective discrete supplementary control for improving the dynamic performance of faulted power systems and preventing instabilities. The sensitivity of the transient energy function (TEF) with respect to changes in the amount of dropped generation is used during the training phase of ANNs to assess the critical amount of generator shedding required to prevent the loss of synchronism. The learning capabilities of neural nets are used to establish complex mappings between fault information and the amount of generation to be shed, suggesting it as the control signal to the power system operator.

DOI:10.1049/ip-c.1992.0060

出版商:IEE    

年代:1992

数据来源: IET

摘要:

This paper describes the procedure and approach taken in constructing an expert system for practical application in alarm processing. Practical considerations include the need for rapid speed of analysis, a good user interface, easy maintainability of the knowledge base, and ability to cope with missing or uncertain input alarm data. The strategies adopted in tackling these problems are described in detail.

DOI:10.1049/ip-c.1992.0061

出版商:IEE    

年代:1992

数据来源: IET

摘要:

In the piping between the tank of a 40 MVA transformer, originally designed for ONAN/ONAF cooling combination, and its bank of radiators, a propeller oil pump was installed. Characteristic temperature rises were measured before and after installation of the pump. The results were applied to the development of a new algorithm for calculation of windings and oil steady-state temperature rises of ONAN/ONAF/OFAF transformers. The mathematical model is briefly described in the paper, and the basic thermal characteristics of transformers with this combination of cooling types are described. Installation of the oil pump can make transformer cooling more efficient provided that certain conditions are satisfied.

DOI:10.1049/ip-c.1992.0062

出版商:IEE    

年代:1992

数据来源: IET