• Proceedings of the KIPE Conference
• /
• 2013.07a
• /
• pp.514-515
• /
• 2013

본 논문은 해상풍력단지와 같은 대용량 신재생에너지를 송전하는데 적합한 전압형 HVDC(High Voltage DC) 중에서, 최근 실용화되어 많은 연구가 이루어지고 있는 Modular Multi-level Converter HVDC(MMC HVDC)에 대한 새로운 토폴로지를 제안한 내용이다. 대표적인 MMC HVDC는 독일의 R. Marquardt 교수가 제안한 Half-Bridge 모듈을 적용하여 MMC를 구현하는 방식으로 이는 계통에 DC 지락 사고가 발생할 경우 컨버터를 구성하는 모듈에 큰 고장 전류가 흐르게 되고 결국 모듈의 주요 구성품인 IGBT가 소손 될 수 있는 약점을 지니고 있다. 이를 보완하기 위해 각 모듈에 Thyristor를 삽입하거나 새로운 모듈을 적용하는 방식이 제안되었다. 본 논문에서는 DC 지락 고장시 큰 고장 전류를 차단할 수 있는 새로운 모듈 구성을 제안하였다. 또한 제안된 토폴로지에 대한 기본 동작을 설명하고 시뮬레이션을 통해 제안한 방식과 기존의 방식을 비교 분석 하였다.

• Proceedings of the KIPE Conference
• /
• 2013.11a
• /
• pp.133-134
• /
• 2013

현재 LS산전과 한국전력공사의 공동 개발을 통하여 60MW급 ${\pm}80kV$ 전류형 HVDC(High Voltage Direct Current) Transmission System 내 알고리즘 국산화 개발을 진행하고 있다. 제어 알고리즘 여러 레벨(AC Yard Control, Master Control, Pole Control, Phase Control)에서 운전하기 전 여러 고려사항 중 DC Yard 내 DC Switch의 투입/개방의 조건이 있다. 본 논문에서는 이러한 DC Line에 DC Switch의 상태를 효율적으로 제어하는 방법에 대해 소개하고자 한다.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.6
• /
• pp.2319-2328
• /
• 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.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.5
• /
• pp.2077-2082
• /
• 2015

Based on Deutsch assumption, a calculation method on the electric field over the ground surface under HVDC transmission lines in the wind is proposed. Analyzing the wind effects on the electric field and the space charge density the existing method based on Deutsch assumption is improved through adding the wind speed to the ion flow field equations. The programming details are illustrated. The calculation results at zero wind speed are compared with available data to validate the code program. Then the ionized fields which resulted from corona of ±800kV HVDC lines are analyzed. Both the electric field and the current density on the ground level are computed under different wind direction and speed. The computation results are in good agreement with measurements. The presented method and code program can be used to rapidly predict and evaluate the wind effects in HVDC transmission engineering.

• Proceedings of the KIEE Conference
• /
• 2006.04a
• /
• pp.279-281
• /
• 2006

In this paper, we study an approach to design a self-tuning Fuzzy-PI controller in HVDC(High Voltage Direct Current) system. In the rectifier of conversional 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. The above problems are solved by adapting Fuzzy-PI controller for the fire angle control of rectifier.[7] 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 the optimal scaling factors of the Fuzzy-PI controller by Genetic Algorithms. In order to improve Fuzzy-PI controller, we adopt FIS to tune the scaling factors of the Fuzzy-PI controller on line. A comparative study has been performed between Fuzzy-PI and self-tuning Fuzzy-PI controller, to prove the superiority of the proposed scheme.

• KIEE International Transactions on Power Engineering
• /
• v.4A no.4
• /
• pp.178-191
• /
• 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.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.5
• /
• pp.664-668
• /
• 2012

This paper presents the operation strategy of KEPCO(Korea Electric Power COporation) ${\pm}80kV$ 60MW Bipole HVDC system that will be applied between Guemak C/S(converter station) and Hanlim C/S in Jeju island. Unlike intertie HVDC system, this system is located in AC power grid inside. Therefore, the enhancement of system security related with line flow and bus voltages can be major operation strategy. In this paper, in particular, the optimal operation algorithm in the abnormal(not steady state) power system is presented and simulated.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.3
• /
• pp.1052-1059
• /
• 2018

This paper deals with commutation failure of the line-commutated converter high voltage direct current (LCC HVDC) system caused by a three phase fault in the ac power system. An analytic calculation method is proposed to estimate the maximum permissible voltage drop at the LCC HVDC station on various operating point and to assess the area of vulnerability for commutation failure (AOV-CF) in the power system based on the residual phase voltage equation. The concept is extended to multi-infeed HVDC power system as the area of severity for simultaneous commutation failure (AOS-CF). In addition, this paper presents the implementation of a shunt compensator applying to the proposed method. An analysis and simulation have been performed with the IEEE 57 bus sample power system and the Jeju island power system in Korea.

• KEPCO Journal on Electric Power and Energy
• /
• v.4 no.2
• /
• pp.47-53
• /
• 2018

VSC technology is now well established in HVDC and is, in many respects, complementary to the older Line Commutated Converter (LCC) technology. Despite the various advantages of VSC technology, VSC HVDC stations have higher power losses than LCC stations. Although the relative advantages and disadvantages are well known within the industry, there have been very few attempts to quantify these factors on an objective basis. This paper describes methods to determine the operating losses of every component in the valve of VSC-HVDC system. The losses of the valve, including both conduction losses and switching losses, are treated in detail.

• Proceedings of the KIEE Conference
• /
• 2008.04b
• /
• pp.28-30
• /
• 2008

본 논문은 국내 실정에 적합한 초고압 가공 직류 송전(HVDC)선로 설계를 위해서 세계적으로 처음 시도되는 가변 기능을 지닌 Proto Type HVDC 실규모 시험선로의 설계와 구축에 대해 소개한다. 시험선로는 초고압 직류송전시 발생하는 이온의 흐름에 의한 이온전류 밀도, 대전 전압, 지표면 전계강도 등 이온류(Ion류(流))에 의한 전기환경장애 및 코로나 영향을 검토하여 환경 친화적 HVDC 송전선로 설계기준을 도출하는데 있다. 이에 따라 HVDC 실규모 시험선로는 요크, 특수 애자련, 특수 arm을 사용하여 철탑의 극간 배치, 도체 배치 변경 및 지상고 변경이 가능하도록 winch를 채용하여 절연설계 조건의 유동성, 환경, 지지물, 송전기자재, 경제성 및 운용의 효율성을 종합적으로 고려할 수 있도록 특수한 형태로 설계되었으며, 본 논문은 상용 가공 HVDC 송전방식의 적용에 앞서 현재의 상황을 고려한 가공 HVDC 실증시험을 수행하기 위한 시험선로의 설계 및 구축에 대하여 기술하였다.