摘要:

The dispatch of capacitors on a distribution feeder in daily system operation is investigated. The objective is to reach an optimal capacitor dispatching schedule, based on the forecast hourly loads for the next day, such that the total feeder loss in a day is minimised. The constraints that must be taken into account include the maximum allowable number of switching operations in a day for each capacitor, and the voltage limits on the feeder. An approach based on dynamic programming is presented to reach such an optimal schedule. To demonstrate the effectiveness of the proposed approach, the dispatch of capacitors on a distribution feeder within the service area of Taipei West District Office of Taiwan Power Company is investigated. It is concluded that a greater loss reduction can be achieved by the optimal capacitor dispatch than by the fixed-schedule dispatch.

DOI:10.1049/ip-c.1993.0063

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A computer algorithm designed for Monte Carlo production cost simulation is described. The design seeks to enhance the precision of production cost estimation at a reduced computation time compared with the existing approach. The algorithm has three major computer steps: (i) to formulate a state population according to the uptime/downtime of the generating unit, hence to simulate generation availability; (ii) to stratify this population by a mathematical rule and draw sample states out of each stratum; and (iii) to estimate the population mean of unit commitment production costs by the rank statistics of the sample. The stratification rule aims to remove any judgemental input and to render the stratification process entirely mechanistic. The estimator, given by rank statistics of the sample, can avoid identification of the regression model and thus save computation time. The algorithm has been evaluated and compared numerically with the existing approach. Hence, the effectiveness on precision improvement is demonstrated.

DOI:10.1049/ip-c.1993.0064

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The paper presents the application of a new impedance relaying principle to a Teed feeder. The relay design is immune from false tripping owing to power swings or prefault load conditions. This has been achieved by extracting and using prefault and superimposed components of relaying voltages and currents. Results are presented for earth faults on a Teed feeder configuration. Relay trip time is typically in the range 11 to 20 ms and is plotted as a surface against prefault power angle and fault point on wave angle.

DOI:10.1049/ip-c.1993.0065

出版商:IEE    

年代:1993

数据来源: IET

摘要:

State estimation which uses redundant real-time telemetry to estimate the system state is considered to be one of the essential parts of the modern energy management system. Owing to modelling restrictions in a multiple injection bus, many of the injection measurements at a bus, in certain circumstances, are not usable, and the estimated net injection cannot be correctly distributed among the individual injections. Two new methods are proposed to model the multiple injection bus. Test results indicate that the proposed methods cannot only utilise all available measurements but also provide a convenient way of estimating individual injections contributing to a bus.

DOI:10.1049/ip-c.1993.0066

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Stabilising torsional oscillations using a single input multiple output (SIMO) static VAR controller is investigated. An eigenstructure assignment technique is applied to design it. The designed controller can be easily implemented by a multiple proportion integral (MPI) controller using medium pressure turbine speed, two low pressure turbine speeds, and generator shaft speed as the feedback signals. Eigenvalue analyses under a wide range of series capacitor compensations and loading conditions, time domain simulations under a pulsed torque disturbance, and fast Fourier transform (FFT) analyses for system behaviour are all performed to demonstrate the effectiveness of the proposed controller.

DOI:10.1049/ip-c.1993.0067

出版商:IEE    

年代:1993

数据来源: IET

摘要:

When HVDC schemes are used to join AC systems of different frequencies, frequencies other than the well known characteristic harmonics are produced in the AC systems, and these are often called interharmonics. This paper examines these interharmonics and shows that, for HVDC schemes with low DC side reactance, another set of interharmonics will exist only on the DC side. These are a function of the impedance of the convertor seen from the DC side. It is shown that this impedance is time varying and, by modulation theory, will produce DC side harmonic frequencies some of which may be at low frequency. It is also shown that the amplitudes of characteristic harmonics and interharmonics will be changed by this effect. The method based upon modulation theory is compared to the results of a time domain computer simulation. The results shown will also be applicable to variable frequency motor drives.

DOI:10.1049/ip-c.1993.0068

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The method presented enables the design digital FIR filters satisfying specific frequency characteristics with auxiliary constraints. Such filters make it possible to estimate in realtime the parameters of fundamental current and voltage waveforms encountered in electrical power systems. The problem of design is converted to an optimisation problem with constraints using the standard least-squares criterion. The minimisation problem using the Lagrange multiplier method is mapped to a simpler problem of solving a set of linear equations. Using this method we optimise the selection of algorithms for particular applications.

DOI:10.1049/ip-c.1993.0069

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A method is proposed for identifying the critical cluster of machines, i.e. the machines responsible for loss of synchronism in a power system following a large disturbance. It is based on the conjecture that the loss-of-synchronism condition can be recognised by, first, considering ‘near-critically cleared trajectories’ of the machines and, secondly, observing how they are organised near the system's unstable equilibrium point. The term ‘near-critically cleared trajectories’ is meant to imply the swing curves of the system in the postfault-phase and is computed for a fault-clearing time that is slightly larger than the actual critical clearing time. To realise the above, the method uses the extended equal-area criterion. This direct criterion makes it possible to assess a convenient clearing time for computing the swing curves; to determine the system's unstable equilibrium point with great ease; and to select the critical machines by observing them at the time corresponding to this unstable equilibrium point. It also makes the speed of critical-cluster identification compatible with real-time requirements. Examples are given using the IEEE test system to illustrate the essential features: reliability in correctly identifying the critical clusters, robustness with respect to its capacity to do so under very stringent conditions, and effectiveness concerning its ability automatically to identify critical clusters of any size, i.e. irrespective of the number of machines that they contain.

DOI:10.1049/ip-c.1993.0070

出版商:IEE    

年代:1993

数据来源: IET

摘要:

This in-depth introduction to chaos in an electrical power system presents techniques for recognising and classifying chaotic behaviour. A cascade of period-doubling bifurcation, which leads to chaos, is observed. Results on a sample power system are presented. The practical significance of chaos for power system operation is also discussed.

DOI:10.1049/ip-c.1993.0071

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The method for reliability analysis of industrial distribution systems presented in this paper combines a Monte Carlo simulation with an electrical network model. The Monte Carlo simulation generates fail and restore events in stochastic components. The flexibility of the Monte Carlo simulation made it possible to include ageing of components and preventive maintenance. As industrial loads are often sensitive to short-duration voltage sags, the influence of these sags had to be included in the model. This is done by using the maximum permissible voltage sag at the load nodes as an interruption criterion. The occurrence of a short-circuit and the intervention by the protection are modelled in detail. Mal-trips as well as fail-to-trip of the protection are included. The method presented in this paper is suitable for industrial (and other) distribution systems where sensitive loads are present, where maintenance of components is important and/or where the behaviour of the protection influences the reliability.

DOI:10.1049/ip-c.1993.0072

出版商:IEE    

年代:1993

数据来源: IET