摘要:

A micromachine model of a large turbogenerator is described. Compensation was applied to the machine, imparting to it realistic dynamic behaviour despite intrinsically high losses. The model's performance is demonstrated by the simulation of fault-throwing tests on a 120 MW machine. The results obtained are compared with those from a typical digital model and show the dynamic model to have a superior overall performance.

DOI:10.1049/ip-c.1987.0040

出版商:IEE    

年代:1987

数据来源: IET

摘要:

The paper illustrates a unified probability technique entitled the ‘load-modification method’ to evaluate generating-capacity reliability. The method is essentially a process of modifying a given load-duration curve with a generating-capacity distribution to give an equivalent load model. The technique presented has the unique ability of maintaining the identity of each individual generating unit in the system throughout the calculation process. This makes the method capable of incorporating the limited energy characteristics of hydro stations or other facilities in the analysis. The technique developed has also been utilised to incorporate load-forecast uncertainty considerations and extended to include interconnected systems in the evaluation. The paper describes and illustrates the approach in single and interconnected systems by simple numerical system examples. Selected studies using the IEEE reliability test system are conducted to illustrate the application of the method.

DOI:10.1049/ip-c.1987.0043

出版商:IEE    

年代:1987

数据来源: IET

摘要:

A more general approach to the matching procedure of an arbitrary load to a nonlinear energy source is presented. The matching procedure is required to assure a maximum power transfer to the load. The matching system is modelled by a linear network, capable of transforming DC power as well as AC power, which is characterised by a transformer matrix. The load and energy-source time variations call for a transformer with a controlled time-variable transfer ratio (TVT). The matching procedure is analysed and discussed. As a practical case, the matching of a photovoltaic (PV) array to a DC motor is studied. The theoretical results are compared to experimental ones. These results allow the determination of the operation and the starting-torque gain (and its maximum value) of the drive system. The torque gain is defined as the ratio of the torque in a matched system to the one in the system without a matching device. By using the TVT it has been found that the torque gain depends on the characteristics of the energy source (say, a PV array) and the electric motor. This study shows in which cases the use of a matching device is recommended and what is the technical improvement of the system. The relatively low costs of the matching device (1–2%) compared with the cost of PV array also helps to determine the economic benefit.

DOI:10.1049/ip-c.1987.0044

出版商:IEE    

年代:1987

数据来源: IET

摘要:

Two reliability models are presented for load curtailment due to transmission outages overlapping with periods of high load. The models give reliability indices of frequency and annual duration of load curtailment. Formulas are derived for the indices, which can handle different types of transmission-component downtime distribution.

DOI:10.1049/ip-c.1987.0047

出版商:IEE    

年代:1987

数据来源: IET

摘要:

A new technique for constructing dynamic equivalents of power systems is developed. The method identifies the important modes of the system utilising a performance index based on the notions of controllability and observability. The system state variables corresponding to the retained modes are identified by inspection of the elements of the sentivity matrix relating the eigen-values to the state variables. The suitability of the method for obtaining reduced-order models of power systems for dynamic-control purposes is demonstrated on a single-machine infinite-bus system. Several reduced-order models are produced and their accuracy discussed.

DOI:10.1049/ip-c.1987.0048

出版商:IEE    

年代:1987

数据来源: IET

摘要:

This paper considers the sensitivity of the load-flow solution to model parameters when load models of the exponential form are incorporated. Several test systems are considered. Computational experience with Newton's method applied to solve the resulting load-flow problems is given. The effects of model parameters and system characteristics on the convergence of the method and on the resulting solutions are highlighted. Our results indicate that the higher values of model parameters yield more significant changes in the load-flow results from the conventional load-flow solution. For the same system, the effect of load modelling is more pronounced at heavier loads than at normal loads. For systems with high capacitive loads, the effects of model parameters are more significant. We also conclude that Newton's method fails to converge for cases where the capacitive effect is high combined with a high reactive-power model exponent even though the application of Newton's method to the conventional problem is successful.

DOI:10.1049/ip-c.1987.0049

出版商:IEE    

年代:1987

数据来源: IET

摘要:

On the basis of hydrodynamic theory and of data obtained by measurement on largescale models, a method is presented for calculating the overall oil flow and its components through the individual transformer cooling ducts in the case of forced, directed oil circulation. Following a preliminary hydraulic calculation it is possible to suggest suitable design adjustments so as to render the temperature-rise increments in the individual ducts mutually equalised, thus achieving optimum utilisation of the circulating oil. The calculated oil velocities in the individual ducts permit the heat-transfer coefficients to be determined reliably; the oil/air temperature gradients can be established from the known rates of oil flow through the ducts of the coolers.

DOI:10.1049/ip-c.1987.0050

出版商:IEE    

年代:1987

数据来源: IET