• KEPCO Journal on Electric Power and Energy
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• v.5 no.4
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• pp.295-309
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• 2019

This paper demonstrates that the verification and analysis of the increase of hosting capacity of distributed energy resources in distribution system for the high penetration of distributed energy resources. In the case of generally designed distribution feeders in South Korea, it can host up to 10 MVA of distributed energy resources and the over voltage due to reverse power flow is prohibited beyond the range by the law of electric utility. However, it should take into consideration that there are some factors of extra hosting capacity such as generation characteristics of distributed energy resources and minimum loads that always exist to distribution system. For these reason, we choose a specific distribution system hosted 10 MVA of distributed energy resources monitored by distribution system operator and verify the impact of increasing hosting capacity such as power flow and voltage profile of distribution system. By the result, we could find that it is possible to increase the hosting capacity and define the factors to expand the hosting capacity of distributed energy resources in distribution system.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.522-532
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• 2017

In this study, we propose a fault analysis method for a power distribution grid with PCS-based DERs. We first explain the characteristics of a PCS-based DER. According to the characteristics, the DER is considered as a current-controlled voltage source, which produces varying voltages within a certain limit so that currents equal to given references flowing from the DER to the grid (currents controlled). So, we introduce the symmetrical equivalent models in the form of varying voltage source for fault analysis and then, construct a convex optimization problem to solve the fault problem associated with the equivalent models and grid conditions. Thus, the proposed method enables to perform a proper fault analysis considering the characteristics of the DER, which are currents controlled, voltage limited, and unity power factor achievement. To verify the validity of the proposed method, we perform computer simulations with the proposed method and with MATLAB Simulink, and the results are compared.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.4
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• pp.569-575
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• 2016

In this paper, we propose a method to develop a static equivalent model of an inverter-based distributed energy resource (DER), where the model is used for a steady-state fault analysis of a power grid. First, we introduce the characteristics of an inverter-based DER as well as its general configuration. Then, we derive the equivalent model of the DER on the basis of the characteristics. Last, the performance of the proposed method is proven by the results of computer simulations.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.371-372
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• 2014

This review focuses on grid-connected technology for distributed energy resources(DER). The grid-connected technology is categorized into three classifications: 1) protection function; 2) power quality improvement function; 3) grid stabilization fuction. Grid codes comparison of Japan, USA, EU and Korea is also described in the paper.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.461-462
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• 2015

세계적으로 마이크로그리드에 이목이 집중되고 있는 현재 상황에서 DER(Distributed Energy Resources : 분산형 독립전원)의 역할이 대두되고 있다. 캠퍼스 마이크로그리드는 대학교의 캠퍼스를 하나이상의 DER로 선정하여 피크 시 교내 전기수요의 일부분을 해소할 수 있는 전력망 기반의 네트워크 시스템이다. 해외에서는 이미 캠퍼스 마이크로그리드 성공사례를 보여주었고, 이후 많은 캠퍼스에서 캠퍼스 마이크로그리드를 벤치마킹하고 있다. 본 논문에서는 캠퍼스 마이크로그리드에 필요한 DER을 구성하기 전 캠퍼스 내의 건물별, 계절별 전력수요 특성을 분석하고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.932-938
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• 2017

This paper presents the structure of an energy management system for distributed energy resources of a grid-connected microgrid. The energy management system of a grid-connected microgrid collects information of the microgrid such as the status of distributed energy resources and the time varying pricing plan through various protocols. The energy management system performs forecasting and optimization based on the collected information. It derives the operation schedule of distributed energy resources to reduce the microgrid electricity bill. In order to achieve optimal operation, the energy management system should include an optimal scheduling algorithm and a protocol that transfers the derived schedule to distributed energy resources. The energy management system operates as a rolling horizon controller in order to reduce the effect of a prediction error. Derived control schedules are transmitted to the distributed energy resources in real time through the international standard communication protocol.

• Journal of Power Electronics
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• v.12 no.1
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• pp.181-192
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• 2012

The increased penetration of Distributed Energy Resources (DER) is challenging the entire architecture of conventional electrical power system. Microgrid paradigm, featuring higher flexibility and reliability, becomes an attractive candidate for the future power grid. In this paper, an overview of microgrid configurations is given. Then, possible structure options and control methods of DER units are presented, which is followed by the descriptions of system controls and power management strategies for AC microgrids. Finally, future trends of microgrids are discussed pointing out how this concept can be a key to achieve a more intelligent and flexible power system.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.519_520
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• 2009

신재생 에너지원을 포함한 대부분의 소용량 분산전원(DER : Distributed Energy Resource)은 22.9 KV 이하의 저압 배전계통에 분포하게 된다. 배전계통에 도입되는 분산전원(DER)에 의한 역조류 문제는 수용가 단의 전압상승 문제를 야기 시킬 뿐 아니라 보호계전 시스템의 전반적인 재검토를 필요로 한다. 출력 제어가 불가능한 분산전원(DER)의 도입량 증가에 따른 무효전력의 수급문제는 기존의 배전망 운영의 개념으로는 효율적인 제어가 어려우며, 유효전력의 급변에 의한 문제도 배전 지역별로 어느 정도 안정화 시킬 필요가 있다. 이를 위해서는 배전 계통운영에도 Energy Management System(D-EMS)의 도입이 필요할 것으로 사료된다. 본 논문은 D-EMS 도입 및 스마트그리드 체제로의 이행을 위한 통신네트워크의 아키텍처 수립을 위한 기능분석 결과이다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.375-383
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• 2015

The virtual power plant (VPP) is a new technology to achieve flexibility as well as controllability, like traditional centralized power plants, by integrating and operating different types of distributed energy resources (DER) with the information communication technology (ICT). Though small-sized DERs may not be controlled in a centralized manner, these are more likely to be utilized as power plants for centralized dispatch and participate in the energy trade given that these are integrated into a unified generation profile and certain technical properties such as dispatch schedules, ramp rates, voltage control, and reserves are explicitly implemented. Unfortunately, the VPP has been in a conceptual stage thus far and its common definition has not yet been established. Such a lack of obvious guidelines for VPP may lead to a further challenge of coming up with the business model and reinforcing the investment and technical support for VPP. In this context, this paper would aim to identify the definition of VPP as a critical factor in smart grid and, at the same time, discuss the details required for VPP to actively take part in the electricity market under the smart grid paradigm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2157-2164
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• 2010

Microgrid is generally defined as cluster of small distributed generators, energy storages and loads. Through monitoring and coordinated control, microgrid can provide various benefits such as reduction of energy cost, peak shaving and power quality improvement. In design stage of microgrid, system dynamic simulation is necessary for optimizing of sizing and siting of DER(distributed energy resources). As number of the system components increases, simulation time will be longer. This problem can restrict optimal design. So we used simplified modeling on energy sources and average switching model on power converters to reduce simulation time. The effectiveness of this method is verified by applying to prototype microgrid system, which is consist of photovoltaic, wind power, diesel engine generators, battery energy storage system and loads installed in laboratory. Simulation by Matlab/Simulink and measurements on prototype microgrid show that the proposed method can reduce simulation time not sacrificing dynamic characteristics.