Wook-Won Kim

Determining the Optimal Capacity of Renewable Distributed Generation Using Restoration Methods

This paper proposes a methodology to determine the optimal capacity of renewable distributed generation (RDG). The objective in this paper is to maximize cost-savings of energy not supplied (ENS) as well as cost-savings of energy loss according to RDG installation in a distribution network. Additionally, in order to achieve this multi-objective optimization problem, both a restoration matrix and restoration availability are newly proposed. In this case study, a practical Korea Electric Power Corporation (KEPCO) system is presented and discussed, demonstrating the performance and effectiveness of the proposed methods.

Operation Strategy of Multi-Energy Storage System for Ancillary Services

Energy storage systems (ESSs) used for ancillary purposes in power systems have different capacities and output characteristics, and so need to be scheduled and operated together based on their state of charge rather than individually. This paper proposes a simple but effective method to allocate the energy required for spinning reserve or frequency regulation, properly to each ESS within a multi-ESS with the aim of improving system reliability. For this, an ESS reliability model is first proposed, and the reliability of the entire system is then evaluated using reliability models for other utilities such as conventional generators and renewable energy sources. To better demonstrate the improvement in reliability, two new reliability indices are introduced besides the existing indices: loss of frequency probability and loss of duration probability. Through case studies, it is shown that the required power is more effectively distributed across each ESS by the allocation method and thus the method can contribute to securing more spinning reserve and alleviating more frequency fluctuation, rather than the conventional method.

Reliability cost of battery with wind farm

By introducing RPS(Renewable Portfolio Standard) for reduction of greenhouse gas, Renewable energy has becoming widespread gradually. Due to a large number of advantages, wind power, which is one of Renewable energy, has standing in the spot-light rather than other Renewable energy. Wind power, however, is difficult to control output and because of severe output fluctuation. It would cause some problems when it is connected with system. Using battery as a solution for these problems has been researched all over the world. In this paper, the reliability modeling of wind farm connected battery and reliability evaluation of system are executed. Also the optimum battery capacity is selected through evaluating reliability cost.

Evaluation of the charging effects of electric vehicles on power systems, taking into account optimal charging scenarios

This paper aims to develop a management method considering load demand for electric vehicle charging. The method developed by means of modeling a stochastic distribution of charging and a demand dispatch calculation. Optimization processes have proposed to determine optimal demand shifting so that charging costs and demands can possibly be managed. The time of use electricity rate has been put into practice to change the tendencies of charging time. Nevertheless, since it focuses only minimizing costs of charging from vehicle owners, loads would be concentrated at a certain time and form a new peak load. The purpose of this paper is to suggest a scenario of load leveling. Therefore charging costs and demands can be managed suitably considering the discordance between electrical prices and system load fluctuations. In case study results, charging patterns and daily demands in the areas are investigated. And optimum solutions are conducted regarding costs and operation aspects by determining demand distribution proportions.

Evaluation of distribution reliability with superconducting fault current limiter

Recently big fault currents flow in a network. The fault current will exceed capacity of circuit breakers soon and all the various rational solutions to solve this problem are taken into account. Under these circumstances, superconducting fault current limiter(SFCL) is a new alternative in the viewpoint of technical and economic aspects. This study presents operation processes for a resistive-type of SFCL, and it proposes reliability model for the SFCL. When a SFCL is installed into a network, the contribution of decreased fault currents to failure for distribution equipments can be quantified. As a result, it is expected that a SFCL makes the reliability of adjacent equipments on existing network improve and these changes are analyzed. We propose a methodology to evaluate the reliability in the distribution network where a SFCL is installed considering a reliability model for SFCL and reliability changes for adjacent equipments which are proposed in this paper.

A Study on the Evaluation of Distribution Reliability Considering Reliability Model for a Resistive-Type of Superconducting Fault Current Limiter

Recently fault currents are increasing in a network. It is caused by increase in electric demand and high penetration of distributed generation with renewable energy sources. Moreover, distribution network has become more and more complex as mesh network to improve the distribution system reliability and increase the flexibility and agility of network operation. Accordingly, the fault current will exceed capacity of circuit breakers soon and all the various rational solutions to solve this problem are taken into account. Under these circumstances, superconducting fault current limiter(SFCL) is a new alternative in the viewpoint of technical and economic aspects. This study presents operation processes for a resistive-type of SFCL, and it proposes reliability model for the SFCL. When a SFCL is installed into a network, the contribution of decreased fault currents to failure for distribution equipments can be quantified. As a result, it is expected that a SFCL makes the reliability of adjacent equipments on existing network improve and these changes are analyzed. We propose a methodology to evaluate the reliability in the distribution network where a SFCL is installed considering a reliability model for resistive-type of SFCL and reliability changes for adjacent equipments which are proposed in this paper.

Optimal Clustering of Energy Storage System for Frequency Regulation Service Considering Life Degradation

Recently, many countries have placed great attention on energy security and climate changes. Governments are promoting the construction of renewable energy projects with regulatory support in Korea. Despite an increasing penetration of renewable resources, however, the photovoltaic and wind power are underutilized due to the endemic problems such as difficulties of output control and intermittent output. The Energy Storage System (ESS) is proposed as a good solution for solving the problems and has been studied in both the private business and the government. However, because of inefficient aspects, the research has been carried out for improving high costs and a small capacity. In addition, the ESS is currently installed for using only one purpose which is frequency regulation or transmission congestion relief such that has an economic limitation. Therefore, methods which are becoming economically justifiable to increase the penetration of the ESS is required. Thus, this paper presents in terms of operation efficiency to improve economic feasibility of the ESS currently used. mainly, there are two aspects for the operation efficiency. Firstly, it is intended to improve the utilization rate through a process that can utilize the ESS for various purposes. It is necessary to be able to use for other purposes by classifying and clustering for increasing the efficiency of availability. The clustering method is proposed to conduct the grouping the ESS. Especially, it is proposed to utilize ESS for frequency regulation service which is the one of ancillary services in the power system. Through case studies, it is confirmed to secure the necessary resources by clustering small size ESS.

Optimal Configuration Algorithm for ESS with Renewable Energy Resources Considering Peak-shaving Effects

A power system configuration has been increasingly advanced with a number of generating units. In particular, renewable energy resources are widely introduced due to the environmental issues. When applying the renewable energy sources with the ESS (Energy Storage System), the ESS is the role of a potential generating resource in the power system while mitigating the output volatility of renewable energy resources. Thus, for applications of the ESS, the surrounding environment of it should be considered, which means that capacity and energy of the ESS can be affected. Moreover, operation strategy of the ESS should be proposed according to the installation purpose as well as the surrounding environment. In the paper, operation strategy of the ESS is proposed considering load demand and the output of renewable energy resources on a hourly basis. Then, the cost of electrical energy is minimized based on the economic model that consists of capital cost, operation cost, fuel cost, and grid cost for a year. It is sure that peak-shaving effects can be achieved while satisfying the minimum cost of electrical energy.

An Optimal Location of Superconducting Fault Current Limiter in Distribution Network with Distributed Generation Using an Index of Distribution Reliability Sensitivity

As electric power demand of customers is constantly increasing, more bulk power systems are needed to install in a network. By development of renewable energies and high-efficient facilities and deregulated electricity market, moreover, the amount of distributed resource is considerably increasing in distribution network consequently. Also, distribution network has become more and more complex as mesh network to improve the distribution system reliability and increase the flexibility and agility of network operation. These changes make fault current increase. Therefore, the fault current will exceed a circuit breaker capacity. In order to solve this problem, replacing breaker, changing operation mode of system and rectifying transformer parameters can be taken into account. The SFCL(Superconducting Fault Current Limiter) is one of the most promising power apparatus. This paper proposes a methodology for on optimal location of SFCL. This place is defined as considering the decrement of fault current by component type and the increment of reliability by customer type according to an location of SFCL in a distribution network connected with DG(Distributed Generation). With case studies on method of determining optimal location for SFCL applied to a radial network and a mesh network respectively, we proved that the proposed method is feasible.