• 센서학회지
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• 제32권3호
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• pp.199-206
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• 2023

This study presents a novel monitoring technique for underwater high-voltage direct current (HVDC) cables based on the Distributed Acoustic Sensor (DAS). The proposed technique utilizes vibration and acoustic signals generated on HVDC cables to monitor their condition and detect events such as earthquakes, shipments, tidal currents, and construction activities. To implement the monitoring system, a DAS based on phase-sensitive optical time-domain reflectometry (Φ-OTDR) system was designed, fabricated, and validated for performance. For the HVDC cable monitoring experiments, a testbed was constructed on land, mimicking the cable burial method and protective equipment used underwater. Defined various scenarios that could cause cable damage and conducted experiments accordingly. The developed DAS system achieved a maximum measurement distance of 50 km, a distance measurement interval of 2 m, and a measurement repetition rate of 1 kHz. Extensive experiments conducted on HVDC cables and protective facilities demonstrated the practical potential of the DAS system for monitoring underwater and underground areas.

• 전기학회논문지
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• 제62권12호
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• pp.1647-1656
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• 2013

Although the demand for electricity has been increasing these days, it becomes more difficult to find new sites for large-scale power generation plants near urban areas due to environmental and economic issues. Therefore, new power plants are forced off to rural or desolate coastal areas. As a result, there is significant regional imbalance in power generation and consumption between urban and rural areas in South Korea. This paper investigates the feasibility of high-voltage DC (HVDC) system as a candidate for electric power transmission system from east-coastal sites to metropolitan area. To this end, this paper analyzes transient stability and dynamic impact of a HVDC transmission system and compares the results to conventional high-voltage AC (HVAC) transmission systems via PSS/E simulation. This paper also examines the effect of HVDC system to voltage variation and low-frequency resonance in the neighboring buses in the grid using ESCR(Effective Short Circuit Ratio)과 UIF(Unit Interaction Factor) indices.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.100-101
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• 2014

HVDC의 보호요소 중 본 논문에서는 변환용 변압기부터 DC송전선로까지를 보호구간으로 삼는 DC Protection을 제주실증단지에 실제 적용시킨 사례에 대하여 기술한다. 보호구간은 어떻게 나뉘며 어떠한 보호요소들이 어떻게 동작하는지를 기술한다.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2319-2328
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• 2018

This paper introduces a control method for a transformerless MMC-HVDC system. The proposed method can effectively control the grid currents of the MMC-HVDC system under unbalanced grid conditions such as a single line-to-ground fault. The proposed method controls the currents of the positive sequence component and the negative sequence component without separating algorithms. Therefore, complicated calculations for extracting the positive sequence and the negative sequence component are not required. In addition, a control method to regulate a zero sequence component current under unbalanced grid conditions in the transformerless MMC-HVDC system is also proposed. The validity of the proposed method is verified through PSCAD/EMTDC simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.432-434
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• 1997

In order to find the steady-state operating condition of HVDC system interacting with AC power system, the load flow calculation of AC/HVDC system is performed. For the calculation, each generating unit is modeled by an equivalent voltage source and coupled impedance. The rectifier station is modeled by a controlled DC voltage source. EMTP simulation of the AC/HVDC system is also performed to verify the result of the load flow calculation.

• KIEE International Transactions on Power Engineering
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• 제4A권4호
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• pp.178-191
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• 2004

This paper presents a new approach to HVDC system control for damping subsynchronous oscillation (SSO) involving HVDC converters and turbine generator shaft systems. This requires a novel eigenvalue analysis (NEA) program, derivation of HVDC system modeling considering steady-state conditions and dynamic conditions in the combined AC/DC system, and an appropriate control scheme. The method suggested makes possible the design of a subsynchronous oscillation damping controller (SODC) to provide positive damping torque for the range of torsional modes in combined AC/DC systems. There are three steps involved in the design of a SODC； first the worst torsional mode is determined using the NEA program, next the SODC parameters are designed for the range of that torsional mode, and then finally an off-line simultaneous time domain program such as PSCAD/EMTDC is used to verify the parameters of the SODC. The suggested SODC design method is applied to two AC/DC systems, and its practicality is verified using the PSCAD/EMTDC simulation program.

• 대한전기학회논문지:전력기술부문A
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• 제54권4호
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• pp.193-198
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• 2005

As the electrical power industry is restructured, the electrical power exchange is extended. One of the key information used to determine how much power can be transferred through the network is known as available transfer capability (ATC). To calculate ATC, traditional deterministic approach is based on the severest case, but the approach has the complexity of procedure. Therefore, novel approach for ATC calculation is proposed using cost optimization in this paper Cheju Island interconnected HVDC system with mainland in KEPCO (Korean Electric Power Corporation) systems, and the demand of Cheju Island increases about 10 ($\%$) every year. To supply for increasing demand, the supply of HVDC system must be increased. This paper proposed the optimal transfer capability of HVDC system between Haenam in mainland and Cheju in Chju Island through cost optimization. The cost optimization is considered production cost in Cheju Island, wheeling charge through Haenam-Cheju HVDC system and outage cost with one depth (N-1 contingency)

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.219-221
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• 1999

HVDC(High Voltage Direct Current) transmission system was constructed between Cheju island and mainland Haenam and has been operating commercially since 1998. But research activities in this area are not so much. That is caused by the facts that HVDC is large scale system and it is not so easy to implement and to test. Though such simulation tools as RTDS(Real Time Digital Simulator) and EMTDC can be useful, these have limitations for actual control and protective system design. Therefore scaled-down HVDC model was developed for the purpose of researches at operating technique, control and protection methods. The design of this model was based on real Cheju-Haenam HVDC system. And additionally faults simulator such as ground fault, short-circuit and change of impedance in transmission line is equipped for analysis of these faults. Control system of the model was implemented fully digitally. So it is very easy for the researchers to develope control and protection algorithm and to test the performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.158-159
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• 2011

최근 발표된 제5차 전력수급계획에 의하면 제주도에 3번째 HVDC 연계선 설치가 계획되고 있다. 이전까지 설치된 2개의 HVDC는 LCC(전류형) HVDC로써 안정적이고 우수한 성능으로 제주지역의 전력 수급에 기여를 했지만 전압 불안정 문제를 초래할 가능성을 가지고 있다. 따라서 3번째 HVDC는 VSC(전압형)으로 설치하는 것을 고려해야 한다. VSC HVDC는 유무효 전력이 동시에 제어가 가능하다는 장점이 있으나 비싼 가격과 높은 변환 손실, 그리고 작은 용량으로 제한적인 용도로만 사용되어 왔다. 그러나 최근 Multi-Level Converter 기술이 적용되면서 이전의 많은 문제들이 해결되었다. 이 논문에서는 VSC HVDC의 최신 동향에 대해서 간략히 소개하고 제주 전력망에 VSC HVDC가 설치되었을 때의 효과에 대해서 논의하고자 한다.

• 제어로봇시스템학회논문지
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• 제12권3호
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• pp.221-226
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• 2006

In this paper, we study an approach to design a Fuzzy PI controller in HVDC(High Voltage Direct Current) system. In the rectifier of traditional HVDC system, turning on, turning off, triggering and protections of thyristors have lots of problems that can make the dynamic instability and cannot damp the dynamic disturbance efficiently. In order to solve the above problems, we adapt Fuzzy PI controller for the fire angle control of rectifier. The performance of the Fuzzy PI controller is sensitive to the variety of scaling factors. The design procedure dwells on the use of evolutionary computing(Genetic Algorithms, GAs). Then we can obtain factors of the Fuzzy PI controller by Genetic Algorithms. A comparative study has been performed between Fuzzy PI controller and traditional PI controller, to prove the superiority of the proposed scheme.