• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.820-831
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• 2015

In a deregulated electricity market, congestion of the transmission lines is a major problem the independent system operator (ISO) would face. Rescheduling of generators is one of the most practiced techniques to alleviate the congestion. However, not all generators in the system operate deterministically and independently, especially wind power generators (WTGs). Therefore, a novel optimal rescheduling model for congestion management that accounts for the uncertain and correlated power sources and loads is proposed. A probabilistic power flow (PPF) model based on 2m+1 point estimate method (PEM) is used to simulate the performance of uncertain and correlated input random variables. In addition, the impact of direct electricity purchase contracts on the congestion management has also been studied. This paper uses artificial bee colony (ABC) algorithm to solve the complex optimization problem. The proposed algorithm is tested on modified IEEE 30-bus system and IEEE 57-bus system to demonstrate the impacts of the uncertainties and correlations of the input random variables and the direct electricity purchase contracts on the congestion management. Both pool and nodal pricing model are also discussed.

• International Journal of Highway Engineering
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• v.16 no.4
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• pp.127-134
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• 2014

PURPOSES : To operate more efficient traffic management system, it is utmost important to detect the change in congestion level on a freeway segment rapidly and reliably. This study aims to develop classification method of congestion change type. METHODS: This research proposes two classification methods to capture the change of the congestion level on freeway segments using the dedicated short range communication (DSRC) data and the vehicle detection system (VDS) data. For developing the classification methods, the decision tree models were employed in which the independent variable is the change in congestion level and the covariates are the DSRC and VDS data collected from the freeway segments in Korea. RESULTS : The comparison results show that the decision tree model with DSRC data are better than the decision tree model with VDS data. Specifically, the decision tree model using DSRC data with better fits show approximately 95% accuracies. CONCLUSIONS : It is expected that the congestion change type classified using the decision tree models could play an important role in future freeway traffic management strategy.

• Journal of Electrical Engineering and Technology
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• v.7 no.2
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• pp.141-150
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• 2012

The present study examines an efficient congestion management system compatible with the evolving environment. The key is to build an information model shared and exchanged for marketbased solutions to alleviate congestion. Traditional methods for congestion management can be classified into two categories, i.e., the centralized scheme and the decentralized scheme, depending on the extent to which the independent system operator (ISO) is involved in market participants' (MPs) activities. Although the centralized scheme is more appropriate for providing reliable system operation and relieving congestion in near real-time, the decentralized scheme is preferred for supporting efficient market operation. The minimum set of information between the ISO and MPs for decentralized scheme is identified: i) congestion-based zone, ii) Power Transfer Distribution Factors, and iii) transmission congestion cost. The mathematical modeling of the proposed information is expressed, considering its process of making effective use of information. Numerical analysis is conducted to demonstrate both cost minimization from the MP perspective and the reliability enhancement from the ISO perspective based on the proposed information exchange scheme.

• Journal of Power Electronics
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• v.11 no.1
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• pp.90-96
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• 2011

Congestion management is one of the most challenging aspects in the recently deregulated electricity markets. FACTS devices have been shown to be an efficient alternative to control the flow of power in lines, resulting in increased loadability, lower system loss and a reduced cost of production. In this paper, the application of a static series synchronous compensator (SSSC) for the purpose of congestion management of power systems has been studied. A sensitivity-based analysis method is utilized for effective determination of the SSSC location in an electricity market. The method is topology based and it is independent of the system operation point. A power injection p-model is developed for the SSSC in this study. Numerical results based on the modified IEEE 14 bus system with/without the SSSC demonstrate the feasibility as well as the effectiveness of the SSSC for congestion management in a network. The results obtained when using the SSSC to improve system transfer capability and congestion management is encouraging.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.417-424
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• 2003

In this paper, we introduce and analyze a feedback control model of TCP/AQM dynamics. Then, we propose the Pro-active Queue Management (PAQM) mechanism, which can provide proactive congestion avoidance and control using an adaptive congestion indicator and a control function for wide range of traffic environments. The PAQM stabilizes the queue length around a desired level while giving smooth and low packet loss rates independent of the traffic load level under a wide range of traffic environment. The PAQM outperforms other AQM algorithms such as Random Early Detection (RED) [1] and PI-controller [2]

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.670-672
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• 2003

The market participants make plans of bidding and transaction strategies to maximize their own profits in competitive electricity market. Also, It is concerned with transmission congestion in power market. Two methods are generally used for congestion management;nodal pricing and uplift. The participants will have different strategies for their profits in the two methods. This paper analyzes their equilibrium strategies by using the supply function model and congestion methods.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.6
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• pp.63-82
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• 2010

In spite of continuous road construction, traffic congestion has been worsening by radical vehicle's increase and development of surroundings near expressway. Thus, the necessity of traffic management and the needs of provision of traffic information to drivers are raised. In order to solve traffic problems, such as traffic congestion, search for optimal congestion management technique and evaluation of the effect of optimal solution should be examined prior to practice of optimal alternative. However, existing traffic analysis model and simulation programs as tools to search and evaluate optimal alternative are not sufficient to reflect traffic flow characteristics, domestic road and traffic conditions and to link up to Freeway Traffic Management Systems (FTMS). Hence, to use existing traffic analysis and simulation tools are followed by hard work to need a lot of time and cost. Therefore, in this research, Expressway TRaffic Analysis Model (ExTRAM) based on Freeway Traffic Management Systems (FTMS) was developed to apply it into congestion management easily.

• Journal of the Korean Operations Research and Management Science Society
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• v.34 no.1
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• pp.61-83
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• 2009

This study developed a variable demand traffic assignment model by stable dynamics. Stable dynamics, suggested by Nesterov and do Palma[19], is a new model which describes and provides a stable state of congestion in urban transportation networks. In comparison with the user equilibrium model, which is based on the arc travel time function in analyzing transportation networks, stable dynamics requires few parameters and is coincident with intuitions and observations on congestion. It is therefore expected to be a useful analysis tool for transportation planners. In this study, we generalize the stable dynamics into the model with variable demands. We suggest a three stage optimization model. In the first stage, we introduce critical travel times and dummy links and determine variable demands and link flows by applying an optimization problem to an extended network with the dummy links. Then we determine link travel times and path flows in the following stages. We present a numerical example of the application of the model to a given network.

• Asia pacific journal of information systems
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• v.26 no.3
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• pp.427-448
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• 2016

The stochastic phenomena of traffic network condition, such as traffic speed and density, are affected not only by exogenous traffic control but also by endogenous changes in service time during congestion. In this paper, we propose a mixed M/G/1 queuing model by introducing a condition-varying parameter of traffic congestion to reflect structural changes in the traffic network. We also develop congestion indices to evaluate network efficiency in terms of traffic flow and economic cost in traffic operating system using structure-changing queuing model, and perform scenario analysis according to various traffic network improvement policies. Empirical analysis using Korean highway traffic operating system shows that our suggested model better captures structural changes in the traffic queue. The scenario analysis also shows that occasional reversible lane operation during peak times can be more efficient and feasible than regular lane extension in Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3610-3618
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• 2015

The congestion of railway vehicle and station shows up to 220%. Especially, transfer resistance of passenger increase rapidly by the collision of circulation. So increment of travel time, occurrence of safety accidents act as a factor that inhibits the utilization of urban railway station. In this paper, to improve traveling speed and comfort of urban rail passengers, urban transit passenger guidance system using congestion management model is proposed. The congestion management model that can mitigate a recurring/non-recurring congestion is constructed and the preliminary design of the system (middleware system, control system, guidance drive system) is carried out. Passenger Guidance System is configured by step for changing the external data into a form usable by the algorithm, step to perform the congestion management algorithm using the real-time data and historical data, step to control device based on the value that is calculated by congestion management algorithm, step to drive the device based on the information in the control system and circulation guidance devices. In the future, detail design will be performed based on the preliminary design. A prototype of the various devices according to the station structures and locations will be made. The control module of guidance device will be developed.