• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2127-2137
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• 2017

A virtual power plant (VPP) is a system that virtually integrates power resources based on the VPP participating customer (VPC) unit and operates as a power plant. When VPP operators manage resources to maximize their benefits, load reduction instructions may focus on more responsive VPCs, or those producing high profitability, by using VPC resources with high operation efficiency. VPCs may thus encounter imbalance problems during operation. This imbalance in operation time would bring more participation for some VPCs, causing potential degradation of their resources. Such an operation strategy would be not preferable for VPP operators in managing the relationship with VPCs. This issue impedes both continual VPC participation and economical and reliable VPP operation in the long term. An operation algorithm is therefore proposed that considers the operation time of VPC generators for mandatory reduction of power resource consumption. The algorithm is based on constraints of daily and annual operation times when VPP operators of local generators perform capacity-market power transactions. The algorithm maximizes the operator benefit through VPP operations. The algorithm implements a penalty parameter for imbalances in operation times spent by VPC generators in fulfilling their obligations. An evaluation was conducted on VPP operational effects by applying the algorithm to the Korean power market.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.810-819
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• 2016

Uncoordinated charging of large-scale electric vehicles (EVs) will have a negative impact on the secure and economic operation of the power system, especially at the distribution level. Given that the charging load of EVs can be controlled to some extent, research on the optimal charging control of EVs has been extensively carried out. In this paper, two possible smart charging scenarios in China are studied: centralized optimal charging operated by an aggregator and decentralized optimal charging managed by individual users. Under the assumption that the aggregators and individual users only concern the economic benefits, new load peaks will arise under time of use (TOU) pricing which is extensively employed in China. To solve this problem, a simple incentive mechanism is proposed for centralized optimal charging while a rolling-update pricing scheme is devised for decentralized optimal charging. The original optimal charging models are modified to account for the developed schemes. Simulated tests corroborate the efficacy of optimal scheduling for charging EVs in various scenarios.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.3
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• pp.12-23
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• 2007

The purpose of this studγ if to understand problem of present bus scheduling system and to develop optimal bus scheduling model which improve bus passenger's degree of satisfaction(DOS) and bus company's operation efficiency at the same time. This study developed optimal bus scheduling model, which reflected bus passenger's degree of satisfaction(DOS), applied to existing model that summery of bus operation cost($C_o$), passenger queuing time cost($C_{pw}$) and passenger travel time cost($C_{pl}$). And optimal bus scheduling model which developed in this study is optimized that using LINGO program based on linear program. Also by using the general case in Busan, compare total cost of present bus scheduling system and existing scheduling model with total cost of optimal bus scheduling model which reflected bus passenger's degree of satisfaction(DOS).

• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.581-586
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• 2014

Main objects for wastewater treatment operation are to maintain effluent water quality and minimize operation cost. However, the optimal operation is difficult because of the change of influent flow rate and concentrations, the nonlinear dynamics of microbiology growth rate and other environmental factors. Therefore, many wastewater treatment plants are operated for much more redundant oxygen or chemical dosing than the necessary. In this study, the optimal control scheme for dissolved oxygen (DO) is suggested to prevent over-aeration and the reduction of the electric cost in plant operation while maintaining the dissolved oxygen (DO) concentration for the metabolism of microorganisms in oxic reactor. The oxygen uptake rate (OUR) is real-time measured for the identification of influent characterization and the identification of microorganisms' oxygen requirement in oxic reactor. Optimal DO set-point needed for the micro-organism is suggested based on real-time measurement of oxygen uptake of micro-organism and the control of air blower. Therefore, both stable effluent quality and minimization of electric cost are satisfied with a suggested optimal set-point decision system by providing the necessary oxygen supply requirement to the micro-organisms coping with the variations of influent loading.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.486-492
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• 1999

One of the purpose of the reservoir operation is minimizing theinnudation area in the downstream reaches during flood period.l To execute the gate operation properly , it requires lots of real-time data such as rainfall, reservoir level, and water level in the downstrea. Gate operation model was developed with the flood discharge obtained from real-time flood forecasting model and the criterion prepared from the past history of gate operation. Water level in the downstream would be increased by the releasing discharge from the spillway and the area of paddy land flooded in a certain detph and time would be estimated usnig GIS map. Gate operation model was applied to the Yedang reservoir, and the flooded area, depth and time in the paddy land was estimaged.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.708-714
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• 2018

Islanded operation of a microgrid can ensure the reliable operation of the system when a large accident occurs in the main grid. However, because the generation capability of a microgrid is typically limited, a microgrid operator should take islanded operation risk into account in scheduling its generation resources. To address this problem, in this paper we have proposed two unit commitment formulations based on the islanding scenario that reflect the expected and worst-case values of the islanded operation risk. An optimal resource scheduling strategy is obtained for the microgrid operator by solving these optimization problem, and the effectiveness of the proposed method is investigated by numerical simulations.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.1167-1180
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• 2023

Due to the tightened regulatory environment since the Fukushima accident, the capacity factor of Korean nuclear power plants has been declining since 2011. To overcome this circumstance, a shift from 18-month to 24-month cycle operation is being considered in Korea. Therefore, in this study, loading patterns(LPs) for 24-month cycle operation of the Korean standard nuclear power plant(OPR-1000) are suggested and economic evaluations are performed. A single-zone LP with 89 fresh fuels was evaluated to be optimal for 24-month operation of OPR-1000 in terms of economic gain. The 24-month operation of OPR-1000 with this LP gives a profit of 7.073 million dollars per year compared to 18-month operation.

• Journal of Korean Institute of Industrial Engineers
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• v.33 no.4
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• pp.487-493
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• 2007

In this paper, we deal with an optimal software-release problem of determining the time to stop testing and release the software system to the user. The optimal release time problem is considered from maintenance like the periodic distribution of service packs and the unpredictable distribution of patches after the release. Moreover, the environment of software error-detection during operation differs from the environment during testing. This paper proposes the software reliability growth model which incorporates periodic service packs, unpredictable patches and operational environment. Based on the proposed model, we derive optimal release time to minimize total cost composed of fixing an error, testing and maintenance. Using numerical examples, optimal release time is determined and illustrated.

• Structural Engineering and Mechanics
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• v.1 no.1
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• pp.119-135
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• 1993

The paper presents a generalized optimal active control algorithm for earthquake-resistant structures. The study included the weighting matrix configuration, stability, and time-delays for achieving control effectiveness and optimum solution. The sensitivity of various time-delays in the optimal solution is investigated for which the stability regions are determined. A simplified method for reducing the influence of time-delay on dynamic response is proposed. Numerical examples illustrate that the proposed optimal control algorithm is advantageous over others currently in vogue. Its feedback control law is independent of the time increment, and its weighting matrix can be flexibly selected and adjusted at any time during the operation of the control system. The examples also show that the weighting matrix based on pole placement approach is superior to other weighting matrix configurations for its self-adjustable control effectiveness. Using the time-delay correction method can significantly reduce the influence of time-delays on both structural response and required control force.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1582-1590
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• 2004

The purpose of this study is to show the existence of optimal operation conditions for minimum fuel consumption of the gas turbine based combined cycle cogeneration power plant. Optimal operational condition means the optimal distribution of the power generated by each gas turbine and the heat generated by each HRSG. Total fuel consumption is calculated by the sum of the fuels for gas turbines and supplementary boiler. Fuel consumption is calculated by numerical methods of energy equations which contain the power generated from gas and steam turbines, the heat generated by HRSG and the heat extracted from high pressure steam turbine.