摘要:

The paper presents an optimisation scheme for the economic dispatch of electric and steam demands to a cogeneration plant with a tieline and auxiliary boiler facilities. The primary objective of the optimisation scheme is to share both the electric and thermal load demands among the in-plant generating units and the energy purchase facilities to minimise the total energy cost. Depending on the cost parameters, optimum cogeneration can result in selling electricity during utility peak demand hours while purchasing electricity during the local peaks of either electricity and/or steam to reduce the overall cost of the unit product. The optimisation scheme is based on generalized network programming (GNP) which can often solve problems with significantly more variables and constraints that can not be easily solved by other optimisation techniques. This scheme is capable of handling the nonlinear cost functions and the dependent relations between the electric power and steam generation for the cogeneration unit. It is possible to represent the price of selling electricity as well as the cost evaluation of satisfying each steam and electric demand. Also, the proposed scheme has the capability to handle multiple objectives which is beneficial for the system operator.

DOI:10.1049/ip-c.1987.0051

出版商:IEE    

年代:1987

数据来源: IET

摘要:

In the paper, catastrophe theory as a mathematical tool is applied for power-system monitoring, analysis and synthesis, using a linear model of a synchronous machine, tieline and automatic voltage regulator. It is shown that much useful information about the steady-state behaviour of the system may be obtained in this way with minimum computation time.

DOI:10.1049/ip-c.1987.0052

出版商:IEE    

年代:1987

数据来源: IET

摘要:

An efficient algorithm is presented for load-flow solutions in electrical power systems. The algorithm is based on the Newton-Raphson process and uses a partitioned-matrix approach to the Jacobian equation which was previously suggested for array-processor applications. It is shown that this approach is also beneficial when using conventional computer systems. The numerical method and computation techniques employed are described, and their relationship to modern computer architectures is considered. The algorithm is highly efficient for the solution of transmission networks but also has particular advantages for lower-voltage networks, and for difficult or ill conditioned load-flow problems. Computational results, obtained using minicomputer hardware, are given for a variety of networks of up to 734 nodes. The numerical method which has been developed is also applicable to other power-system problems including state estimation and dynamic simulation.

DOI:10.1049/ip-c.1987.0053

出版商:IEE    

年代:1987

数据来源: IET

摘要:

Elaborate control and monitoring structures have been developed for power-system operation. The basic operating structure is hierarchically organised from the main control centre, with the added provision of numerous automatic and protective devices to assist operators in effectively controlling the power grid. Centralised control has proved effective under normal conditions and for a range of disturbances for which the power system has been planned. However for disturbances of greater severity than allowed by planning criteria, this edifice does not avert the threat to the power system. By default, it is assumed that operators can control the consequences of these calamitous disturbances. Experiences throughout the world have shown the fallacy of this assumption. The threat of calamitous system disturbances has been mostly tackled from the aspect of a centralised control. As shown in this paper, a number of insuperable difficulties are created in adopting this approach. Instead, it is possible to utilise a method of distributed intelligence within the existing hierarchical control structure. This paper demonstrates not only the feasibility of this approach, but how it can monitor the system's dynamic reactions to control the after effects of the disturbances. This would allow developments enabling power systems to successfully withstand calamitous disturbances.

DOI:10.1049/ip-c.1987.0055

出版商:IEE    

年代:1987

数据来源: IET

摘要:

A new approach to load management is outlined, having as a major objective, provision for the emergency operation of a power system. This load-management proposal would not inconvenience consumers, yet would be accessible to operators at any time. In an emergency, this immediate load control would greatly enhance the potential for safeguarding the system. This loadmanagement approach extends to individual consumers within distribution networks. Battery installations at selected consumers would back-up portions of the load under local microprocessor control. This control could be provided by a currently available credit and load-management unit (CALMU), which, with its remote interrogation facility, is already cost competitive with conventional metering. The proposal has been conceived as an important component of a systemprotection arrangement which would be capable of countering calamitous disturbances on major power systems. It has also the potential to substantially improve distribution-network security. The stored energy of the battery installations could extend the use of this proposal for normal operations. Not only would it reduce the need for peaking generators and improve the system capacity factor, but it would facilitate the introduction of renewable and alternative generation. Only the normal operational benefits would allow tariff incentives encouraging consumers to meet the capital costs of battery installations.With this policy, the proposal would allow electric utilities, with a modest capital outlay, to significantly raise security levels of their total power grid.

DOI:10.1049/ip-c.1987.0056

出版商:IEE    

年代:1987

数据来源: IET

摘要:

Any disturbance causing a transmissionline overload creates an operational situation which must be quickly controlled. If the line should trip, there is a great danger of cascade tripping of lines, thus leading to system breakup. Five different levels of overload are identified and methods are proposed for an automatic reduction of these transmission-line overloads. The adopted approach recognises that there are two distinct areas of difficulty, moderately and severely overloaded lines, with each requiring a different method of resolution. This has led to the development of two distinct measures which either separately, or in combination, can control the complete range of transmission overloads. By recognising that transmission-line overloads can impinge on the system's reactive-power balance, a computationally simple algorithm has been developed. This would allow moderate line overloads to be reduced by the automatic rearrangement of generator outputs. Severe overloads can impinge on transmission-line protection settings, so that extremely fast measures are required. An extension of strategic load shedding [1, 2] would allow line currents to be reduced below the protection setting prior to its functioning. Generator output rearrangement could then reduce the residual line overload. Alternatively, it may prove expedient to actuate a further level of strategic load shedding before rearranging generation, to correctly control the overload. With its importance in the control of line overloads, the underlying philosophy of strategic load shedding is described.

DOI:10.1049/ip-c.1987.0057

出版商:IEE    

年代:1987

数据来源: IET

摘要:

Local generating facilities in power distribution networks can be used to supply the load, when the bulk supply points become unavailable, to a load point during outage conditions. The purpose of the paper is to describe and demonstrate the modelling and evaluation techniques that are necessary to translate the conceptual ideas of local generation to practical analysis. These techniques construct the relevant statespace diagrams and identify the system down states. The steady-state probabilities of a general state-space diagram are evaluated by applying a set of equations and a computational algorithm to minimise the computer storage and time requirements and eliminate the rounding errors incurred when a conventional Markov approach is used. The algorithm developed is suitable for either computer implementation to analyse complex systems or hand calculations to analyse simple systems. A typical distribution system is analysed which illustrates the additional results and information that can be achieved from the use of these extended system models.

DOI:10.1049/ip-c.1987.0058

出版商:IEE    

年代:1987

数据来源: IET

摘要:

Based on the set theory and the Prolog programming language, the paper develops methods by which the allocation of loads to the busbars of distribution substations may be determined automatically. Starting from the initial possible allocation of loads to the substation busbar sections, a formulation for load allocation is first developed using set theory. The ‘generate evaluate and test’ technique and the depth-first search method are then applied to the solution-seeking process. The formulation is implemented and recursive search procedures are derived using the Prolog language. The Prolog software aid developed includes a complete solution generator from which all hypothetical solutions are generated, an evaluator which prunes invalid solutions, and a tester which produces feasible solutions by checking the load allocation constraints related to the firm capacity of the distribution substations. An application of the methods developed is given for two 11 kV interconnected substations which include 5 busbar sections and 10 ring loads.

DOI:10.1049/ip-c.1987.0059

出版商:IEE    

年代:1987

数据来源: IET

摘要:

This paper describes the features, hardware and software functions of a digital data-acquisition unit designed for monitoring and recording power-system transients. It has been configured for connection, via appropriate isolation units, to system voltage and current transformers. The raw digitised voltage and current quantities can either be stored directly onto magnetic data cartridges or be processed on-line to produce cycle-average voltage, power and frequency quantities before being stored onto the cartridges. These data, arranged in computer-compatible format, can then be readily accessed for off-line analysis work. Two application examples of this recorder, taken from recent field tests performed on a static-reactive-power compensated radial network, are included. The results are discussed and compared with those obtained from simulation studies.

DOI:10.1049/ip-c.1987.0061

出版商:IEE    

年代:1987

数据来源: IET