• KEPCO Journal on Electric Power and Energy
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• v.5 no.4
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• pp.275-286
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• 2019

This paper presents real-time Direct Current (DC) network analysis applications for operation of DC distribution system or DC microgrid. These applications are installed on central Energy Management System (EMS) and provide solutions of DC network operation. To analysis DC distribution network, this paper proposes composition and sequence of applications. Algorithm of applications is presented in this paper. Demonstration tests are performed on DC distribution site in Gochang Power Testing Center of Korea Electric Power Corporation (KEPCO). To verify the performance, developed DC applications installed on EMS. Scenarios for demonstration test of voltage control are presented. Finally, measured data, application output data and simulation data (by PSCAD/EMTDC) are compared and analyze accuracy of applications.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.30-37
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• 2018

Unlike an AC system, a DC system does not cause problems with synchronization, stability, reactive power, system losses, and cost. However, more research is still required for the application of DC Systems. This paper proposes a stable black-start strategy for a stand-alone DC micro-grid, which consists of an energy storage system, photovoltaic generator, wind-turbine generator, diesel generator, and DC loads. The proposed method is very important for avoiding inrush current and transient overvoltage in the power system equipment during restoration after a blackout. PSCAD/EMTDC software was used to simulate, analyze, and verify the method, which was found to be stable and applicable for a stand-alone DC micro-grid.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.87-89
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• 2018

본 논문에서는 양극성 직류 배전 시스템에 사용할 수 있는 절연형 3-레벨 전압 평형기를 제안한다. 전압 평형기는 양극성 부하에서 발생하는 불균등한 전압을 보상해주는 필수적인 전력변환장치이다. 제안하는 1단 구성의 절연형 전압 평형기는 오직 3-레벨 Dual Active Bridge DC-DC 컨버터로만 구성되고, 기존에 전압 벨런싱을 위해 사용되던 추가적인 비절연형 전압 평형기를 필요로 하지 않는다. 따라서 기존 비절연형 전압 평형기에 사용되는 수동 및 능동 소자를 제거함으로써 전력변환 장치의 전체적인 전력 밀도 및 전력 변환 효율을 향상시키는 장점을 가진다. 새롭게 제안하는 스위칭 방식을 통해 3-레벨 전압 평형기가 절연과 전압 벨런싱 기능을 동시에 수행한다. 3 kW급 전압 평형기의 시작품을 이용하여 제안하는 토폴로지와 제어 알고리즘의 성능과 타당성을 실험적으로 검증하였다.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.7
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• pp.199-204
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• 2021

Digital substation refers to a substation that digitizes functions and communication methods of power facilities such as monitoring, measuring, control, protection, and operation based on IEC 61850, an international standard for the purpose of intelligent power grids. Based on the intelligent operating system, efficient monitoring and control of power facilities is possible, and automatic recovery function and remote control are possible in the event of an accident, enabling rapid power failure recovery. With the development of digital technology and the expansion of the introduction of eco-friendly renewable energy and electric vehicles, the spread of direct current distribution systems is expected to expand. MVDC is a system that utilizes direct current lines with voltage levels and transmission capacities between HVDCs applied to conventional transmission systems and LVDCs from consumers. Converting existing lines in substations, where most power equipment is alternating current centric, to direct current lines will reduce transmission losses and ensure greater current capacity. The process bus of a digital substation is a communication network consisting of communication equipment such as Ethernet switches that connect installed devices between bay level and process level. For MVDC linkage to existing digital substations, the process level was divided into two buses: AC and DC, and a system that can be comprehensively managed in conjunction with diagnostic IEDs as well as surveillance and control was proposed.