• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.417-419
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• 2005

This paper presents the effects and the regional power distribution of an increase or a decrease of a power reserve by load flow calculations under seasonal load patterns of each country for the future power shortages faced by the metropolitan areas or by the southeastern area of the South Korea in North-East Asia. In these connections, the types of a power transmission for interconnection consist of the 765kV HVAC and the HVDC. In this paper, the various cases of the power system interconnections in Far-East Asia are presented, and the resulting interconnected power systems are simulated by means of a power flow analysis performed with the PSS/E 28 version tool. The power flow map is drawn from data simulated and the comparative study is done. In this future, a power flow analysis will be considered to reflect the effects of seasonal power exchanges And the plan of assumed scenarios will be considered with maximum or minimum power exchanges during summer or winter in North-East Asia countries.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.395-397
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• 1999

This paper presents a method of improving the power factor and the waveform of A.C line currents and the out waveforms of AC to DC fully bridge converter systems which is achieved by connecting converters in series and parallel. The results of simulation show that the power factor and the source voltage and current waveforms are improved by the method of connecting converter in series, and the controlled input voltage and current waveform using a current limit controller.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권1호
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• pp.105-109
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• 2014

Converter valve cooling device as the heat exchanger, is known as the converter valve's blood circulation system, Inefficiency of the equipment will not only lead to the component overheating damage, but also serious DC system outage. Therefore, reliable HVDC valve cooling system is essential for the HVDC transmission system. In this article, analysis on the two-phase flow heat transfer characteristics and security of the evaporative cooling technology are provided, the technology's advantage and feasibility are discussed.

• 전력전자학회논문지
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• 제21권1호
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• pp.49-57
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• 2016

A modular multilevel converter is widely adapted for a high-voltage direct current power transmission system. This study proposes a design methodology for a novel digital control that mitigates the negative effects caused by time delay, including communication transport delay for a modular multilevel converter. The modeling and negative effect of time delay are analyzed theoretically in a frequency domain, and its compensation methodology based on an inverse model is described fully with practical considerations. The proposed methodology is verified through several simulation results using a modular 21-level converter system.

• Journal of Electrical Engineering and Technology
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• 제7권2호
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• pp.157-162
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• 2012

Wind energy is created in mega-sized wind farms situated kilometers off shore. In fact, two possibilities are considered for the transmission system between the offshore wind farm and the onshore grid: high-voltage direct current and high-voltage alternating current. From this point of view, the current paper aims to compare both systems for a 2 GW wind farm situated 80 km from the Point of Common Coupling on an economic basis using a discounted cash flow analysis. A tool is developed in Microsoft Excel to allow for quick insight in the variation of input parameters.

• 전력전자학회논문지
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• 제23권6호
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• pp.415-423
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• 2018

This study uses a level selection algorithm with fixed sampling frequency for modular multilevel converter (MMC) systems. Theoretically, the proposed method increases the level infinitely while the sampling time remains the same. The proposed method called cluster stream buffer (CSB) consists of several clusters, wherein each cluster is composed of 32 submodules that depend on the level of the submodules in the MMC system. To increase the level of the MMC system, additional clusters are used, and the sampling time between clusters is determined from the sampling time between levels needed for utilizing the entire level from the MMC system. This method is crucial in the control of MMC-type HVDC systems because it improves scalability and precision.

• 조명전기설비학회논문지
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• 제16권2호
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• pp.45-53
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• 2002

본 논문은 두 지역 간에 직렬로 연결된 HVDC 연계시스템의 전력계통 안정화장치와 전력변환기의 적정 파라메터 선정기법을 다루었다. PSS파라메터 선정기법은 구하고자 하는 진상이 되도록 극좌표를 이동시키고, 충분한 댐핑을 얻도록 이득을 조절하는 고전적인 기법이다. 전력변환기의 적정 파라메터는 근궤적기법을 근거로 하여 기준 값의 변화와 시스템의 동요에 충분한 속응력과 안정도를 고려하여 산정한다. 이들 기법으로 구판 제정수로 소신호 및 과도안정도 분석결과는 사례연구시스템의 고유동요 주파수에 적절한 댐핑 효과를 보여주었다. 본 논문에서 사용한 프로그램은 MATLAB을 근거로 한 PST이다.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1471-1481
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• 2014

This paper presents the new power dissipation model of individual switching device in a high-level modular multilevel converter (MMC), which can be mostly used in voltage sourced converter (VSC) based high-voltage direct current (HVDC) system and flexible AC transmission system (FACTS). Also, the voltage balancing method based on sorting algorithm is newly proposed to advance the MMC functionalities by effectively adjusting switching variations of the sub-module (SM). The proposed power dissipation model does not fully calculate the average power dissipation for numerous switching devices in an arm module. Instead, it estimates the power dissipation of every switching element based on the inherent operational principle of SM in MMC. In other words, the power dissipation is computed in every single switching event by using the polynomial curve fitting model with minimum computational efforts and high accuracy, which are required to manage the large number of SMs. After estimating the value of power dissipation, the thermal condition of every switching element is considered in the case of external disturbance. Then, the arm modeling for high-level MMC and its control scheme is implemented with the electromagnetic transient simulation program. Finally, the case study for applying to the MMC based HVDC system is carried out to select the appropriate insulated-gate bipolar transistor (IGBT) module in a steady-state, as well as to estimate the proper thermal condition of every switching element in a transient state.

• 기술혁신연구
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• 제22권4호
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• pp.117-143
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• 2014

기존의 기술 진화 경로 연구는 주로 거시적 동향 분석 수준에서 이루어져 왔으며 포괄적인 기술정책 방향 수립에는 시사점이 있었으나, 기업 기술 및 특허전략에는 활용가치가 낮았다. 2000년대부터 논문 및 특허 등의 데이터를 활용해 미시적인 기술의 진화 경로를 분석하고, 기업 기술전략에 적용하려는 연구가 증가하고 있다. 그러나 대부분 과거 진화 경로의 서술에 그치고 있으며 기술의 진화 또는 파생-융합 등의 변화에 대한 분석은 전문가의 정성적 판단에 상당부분 의존하고 있다. 본 연구에서는 특허 인용 네트워크를 구축해 미시적 기술의 진화 경로를 도출하고, 기술의 진화와 파생을 동적 기술트리를 통해 분석하는 방법론을 제시한다. 동적 기술트리 분석은 기술의 핵심요소를 체계화하고, 신기술 요소의 신규성과 확장성을 평가해 차세대 기술진화와 파생에 대한 정량적 판단을 가능하게 한다. 이를 통해 차세대 신기술과 파생기술에 대하여 파악, 평가, 비교하고 나아가 예측의 토대를 구축한 것이 본 연구의 의의이다. 본 연구의 결과는 기술 및 특허전략과 포트폴리오 구축의 신뢰성을 높일 수 있는 좋은 도구가 될 것이다. 본 연구에서 제안한 방법론을 이용하여 최근 전력산업에서 기존 교류 송전의 대안으로 주목을 받고 있는 초고압 직류송전 시스템 기술을 대상으로 실증분석을 수행하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.151-152
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• 2013

Multilevel Voltage Source Converter HVDC presents a new method for the energy transmission, The multilevel requires the converter bridge includes more than 100 converter modules, for the EMT simulation file, the simulation time increases to several hours; it can depress the research process. In the paper, author describes a method to simulate the multilevel arm based on time-varying equivalent. The result shows the extremely calculation time reduced with almost the same accuracy.