Transmission Network Model Research Articles

Developing a realistic sexual network model of chlamydia transmission in Britain.

BackgroundA national chlamydia screening programme is currently being rolled out in the UK and other countries. However, much of the epidemiology remains poorly understood. In this paper we present a stochastic, individual based, dynamic sexual network model of chlamydia transmission and its parameterisation. Mathematical models provide a theoretical framework for understanding the key epidemiological features of chlamydia: sexual behaviour, health care seeking and transmission dynamics.ResultsThe model parameters were estimated either directly or by systematic fitting to a variety of appropriate data sources. The fitted model was representative of sexual behaviour, chlamydia epidemiology and health care use in England. We were able to recapture the observed age distribution of chlamydia prevalence.ConclusionEstimating parameters for models of sexual behaviour and transmission of chlamydia is complex. Most of the parameter values are highly correlated, highly variable and there is little empirical evidence to inform estimates. We used a novel approach to estimate the rate of active treatment seeking, by combining data sources, which improved the credibility of the model results. The model structure is flexible and is broadly applicable to other developed world settings and provides a practical tool for public health decision makers.

Global state estimation for whole transmission and distribution networks

Traditionally, transmission and distribution state estimators are studied and developed separately. But lots of large cities have their hybrid transmission and distribution networks. In order to face keen competition in market, the requirement of coordinated operation between transmission and distribution systems is now here. Therefore, in order to balance the boundary mismatch between the transmission and distribution network models existing in the results of traditional state estimation methods, the transmission and distribution networks are studied as a whole in this paper. The weighted least squares (WLS) model for global state estimation (GSE) is presented for estimating the global consistent state in the whole network. A novel master–slave-splitting (MSS) iterative method is developed for solving the hybrid GSE problem. In the proposed method, the GSE problem of large scale is split into a transmission state estimation and lots of distribution state estimation sub-problems, which supports on-line geographically distributed computation. In order to fit the different features between transmission and distribution networks, each sub-problem can be solved with different algorithm. Several case studies are carried out, and the accuracy, convergence, efficiency and reliability of the proposed method are validated.

低コストリアルタイムシミュレータ実現のための送電線モデル構築手法の一検討

In modern power systems, it is important to analyze various kindes of dynamic phenomena which appear in the system. When the effectiveness of new power electronics based apparatus, protective relay systems and etc. is tested, a real-time power system simulator is becoming a very effective tool. In general, however, it is very expensive and it is very difficult for beginners to understand how to use it. Therefore, studies on low-cost and easy-use real-time power system simulators have so far been done. We have developed models of power system components for the real-time power system simulator using DSP (Digital Signal Processor) combined with commercial CAD (Computer Aided Design) soft "MATLAB/SIMULINK". The use of commercial softwares can drastically decrease the development cost of the simulator. In this paper, a simplified reduction model of unbalanced three-phase transmission network with mutual impedance is proposed for analysis of various kinds of stability phenomena by use of the digital simulator. The proposed network model is constructed automatically and efficiently even for connection of both current source type models and voltage source type models of power apparatus such as generators, FACTS devices and loads.

An acoustic-logging transmission-network model.

The acoustic logging process can be described as a signal transmission system with a corresponding transmission network model. This model gives the relations between driving-voltage signal, the electrical-acoustic conversion at the source, acoustic properties of the propagation media (borehole fluid and formation around borehole), the pressure response in the borehole, the acoustic-electrical conversion at the receiver and recorded logging signal.

Optimization network flow control and price coordination with feedback: proposal of a new distributed algorithm

The usage of price instruments was found to offer an interesting opportunity for reactive congestion flow control in communication or computer networks where the objective is to maximize the total utility of all traffic sources over their transmission rates. The proposed control mechanisms were, amongst others, based on the Price Method—known also as the Interaction Balance Method—and both synchronous and asynchronous versions were developed. It was, however, so far assumed that the transmission network model was known exactly and that no traffic was lost and the traffic routes were fixed and known to the transmitting sources. In this paper, we formulate the flow control problem in a modified form, allowing in particular for the routing decisions to be hidden from the sources, and recall the concept of the Price Coordination with Feedback (known also under the name of the Interaction Balance Method with Feedback—IBMF). It is then shown that the use of this approach allows for proposing the new distributed algorithm for pricing of network services. The existence of an optimal solution in steady state is proved under reasonable assumptions and the convergence issues are discussed. Two examples are provided to illustrate the operation of the proposed algorithm and to compare its performance with the usage of classical price coordination.

Asymptotic expansions for large closed and loss queueing networks

Loss and closed queueing network models have long been of interest to telephone and computer engineers and becoming increasingly important as models of data transmission networks. This paper describes a uniform approach that has been developed during the last decade for asymptotic analysis of large capacity networks with product form of the stationary probability distribution. Such a distribution has an explicit form up to the normalization constant, or the partition function. The approach is based on representing the partition function as a contour integral in complex space and evaluating the integral using the saddle point method and theory of residues. This paper provides an introduction to the area and a review of recent work.

A transmission network model for multi-area reliability studies

A transmission network suitable for use in multiarea power system reliability models which utilize a Monte Carlo simulation approach is presented. The transmission network model utilizes the REI equivalent, which permits accurate modeling of transmission ties between areas while reducing computational burden and permitting variations in area generating capacity and loads as required in reliability studies. A computationally efficient approach to generation redispatch as required to model mutual assistance between areas in multiarea reliability studies is presented. Sample results are given for the IEEE Std 118-bus test system and a large power pool with 13 areas. >

An improved method of including detailed synchronous machine representations in large power system models for fault analysis

An efficient approach for combining time- and frequency-domain analysis techniques to produce improved fault analysis results is presented in this paper. The developed approach is applied to fault analysis to determine the time-domain solutions for synchronous machine terminal variables while utilizing frequency-domian techniques to model the transmission network. In general, the transmission network is modeled using steady-state AC circuit theory to form a constant impedance network description, while the rotating machines are represented by sets of coupled differential equations. The interface between the time-domain machine models and the frequency-domain transmission network model transforms the differential equation solutions into the appropriate frequency-domain phasors using time series analysis to obtain least-square-error approximations of the phasor magnitudes and angles. The combination of time and frequency-domain analysis allows the total number of calculations required for a solution to be considerably less than the number required for a complete time-domain solution. >

Chronological probabilistic production costing and wheeling calculations with transmission network modeling

The authors present an approach for the integrated analysis of generation and transmission system in terms of production costing and wheeling rate calculations. The methodology is based on the chronological simulation of system operation. Economic dispatch at each state is provided by linearized optimal power flow routines, which can represent network aspects and export/import contracts among utilities. Probabilistic aspects are represented by Monte Carlo sampling of generation capacities, load levels, etc. Marginal costs are calculated at bus level and serve as a basis for the evaluation of wheeling rates. This makes it possible to model complex utility situations for use in power system planning and operations, determination of interchange contracts, and regulatory applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A time-domain approach for distribution and transmission network modeling

A state variable approach based on a time-domain analysis is presented for identifying the parameters of a distribution or transmission network model using actual recorded data. The data used in the model development were simulated data and actual recorded data. The actual recorded data were obtained during normal operating and capacitor switching conditions in a primary distribution feeder. The method describes the network in state variable format, which is applicable to steady-state and transient conditions. The conversion of state variable representation to frequency-domain impedance transfer functions is also presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Stability analysis of power systems by Lyapunov's direct method

The Lyapunov direct method is on the verge of being implemented for assessment of online dynamic security. The main bottleneck has been in the proper characterization of the stability boundary and defining the fault-dependent region of attraction locally around the controlling unstable equilibrium points. Now there is a better understanding of this issue, and hence, a number of algorithms have been proposed. Improved generating-unit models and transmission-network models are now being included in the technique. An overview is presented of the theory, practical implementation, and future research.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A second order load flow technique

This paper presents a second order load flow technique based on the Taylor series expansion of a multivariable function. An algorithm for obtaining digital solutions by the proposed approach is described. Six simplified versions of this algorithm are also discussed. The proposed algorithm and its modifications have been tested by obtaining load flow solutions of a five bus system, the 26 bus Saskatchewan Power Corporation transmission network model and the IEEE 14 bus, 30 bus, 57 bus and 118 bus test systems. The effectiveness of these algorithms is compared with the performance of the Newton Raphson approach and some of the results from these studies are presented.