• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.3
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• pp.263-269
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• 2017

This paper proposes a novel circulating current control method for an MMC-HVDC system based on Vector PI control. The method can suppress second-order harmonics of the circulating currents under balanced and unbalanced grid conditions. The proposed method is robust to grid frequency variation. The effectiveness of the proposed method is verified through frequency response and time domain simulation.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.915_916
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• 2009

최근 산업계에서는 스위칭 손실을 저감하여 효율 및 성능 개선에 대한 다양한 토폴로지가 제안되고 있다. 특히 소프트 스위칭 방식은 낮은 전압과 전류 스트레스를 갖는 장점으로 인하여 절연형 DC/DC 컨버터에서 인덕터 사용 없이 트랜스포머의 누설리액턴스를 사용한 소프트 스위칭에 대한 연구가 활발히 이루어지고 있다. 본 논문에서는 소프트 스위칭 특성을 갖는 새로운 DC/DC 컨버터 형태를 제안한다.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.468-469
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• 2018

본 논문에서는 MMC(Modular Multi-level Converter)타입 전압형 HVDC 서브모듈의 커패시터 용량을 추정하는 방법을 기술하였다. 서브모듈 내 별도의 전류센서 및 계측 시스템을 추가하지 않고 커패시터 용량을 추정하여 안정적인 HVDC 시스템의 동작이 가능하도록 하였으며 시뮬레이션을 통하여 타당성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.111-112
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• 2015

MMC HVDC(Multi-level Modular Converter High Voltage Direct Current)는 현재 차세대 전력망으로써 각광을 받고 있고 그에 대한 연구가 활발하게 진행 중이다. 본 논문에서는 모듈형 멀티레벨 컨버터를 이용한 전압형 HVDC 시스템의 AC 전류제어기에 대하여 기술하고자 한다. 일반적으로 사용되는 회전변환을 통한 DQ전류제어와 PR제어를 사용하여 응답특성을 PSCAD/EMTDC를 통하여 비교 검증하고자 한다.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.344-345
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• 2019

High Voltage Direct Current (HVDC) 시스템은 고압 직류 송전을 위한 시스템으로서 단위 유닛인 서브모듈로 구성된 모듈형 멀티레벨 컨버터 구조를 갖는다. 서브모듈의 신뢰성 확보 및 설계 검증은 HVDC 시스템의 성능과 효율, 크기를 결정짓는 중요한 요소이다. 본 논문에서는 (주)효성이 개발하는 200MW 모듈형 멀티레벨 컨버터 서브모듈의 성능을 검증하기 위한 특성시험을 나타낸다. 특성시험을 통해서 개발 중인 서브모듈의 성능과 보호동작을 검증한다.

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.166-173
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• 2022

A variety of input parameters are taken into consideration while performing a Level 3 PSA. Some parameters related to plume segments, spatial grids, and particle size distribution have flexible input formats. Fine modeling performed by splitting a number of segments or grids may enhance the accuracy of analysis but is time-consuming. Analysis speed is highly important because a considerably large number of calculations is required to handle Level 2 PSA scenarios for a single-unit or multi-unit Level 3 PSA. This study developed a sensitivity analysis supporting interface called MACCSsense to compare the results of the trials of plume segmentation with the results of the base case to determine its impact (in terms of time and accuracy) and to support the development of a modeling approach, which saves calculation time and improves accuracy. MACCSense is an automation tool that uses a large amount of plume segmentation analysis results obtained from MUST Converter and Mr. Manager developed by KAERI to generate a sensitivity report that includes impact (time and accuracy) by comparing them with the base-case result. In this study, various plume segmentation approaches were investigated, and both the accuracy and speed of offsite consequence analysis were evaluated using MACCS as a consequence analysis tool. A simultaneous evaluation revealed that execution time can be reduced using multi-threading. In addition, this study can serve as a framework for the development of a modeling strategy for plume segmentation in order to perform accurate and fast offsite consequence analyses.

• Journal of Power Electronics
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• v.16 no.2
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• pp.522-531
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• 2016

This paper proposes a new NLC (Nearest Level Control) scheme for MMCs (Modular Multilevel Converters), which offers voltage ripple reductions in the DC capacitor of the SM (Sub-Module), the output voltage harmonics, and the switching losses. The feasibility of the proposed NLC was verified through computer simulations. Based on these simulation results, a hardware prototype of a 10kVA, DC-1000V MMC was manufactured in the lab. Experiments were conducted to verify the feasibility of the proposed NLC in an actual hardware environment. The experimental results were consistent with the results obtained from the computer simulations.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.326-332
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• 2018

In this paper, the design process and the control method of the power conversion system (PCS) that consists of a bidirectional DC-DC converter and a 3-level T-type inverter for an energy storage system is presented. Especially the design method of the output LCL filter for a 3-lvel T-type inverter without complex mathematical process are proposed. The validity of the control method and design process in this paper are verified through simulation and experimental analysis.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.1058-1063
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• 2010

In this paper, we designed self-frequency synchronizing circuit using image rejection mixer(IRM) and single-sideband(SSB) up-converter which can effectively eliminate the image frequencies occurred in multi-channel super-heterodyne receivers and help us to match inter-channel phase. Also the self-frequency synchronizing circuit simplifies system because there need no extra devices for making intermediate frequency(IF) by creating the local signal within several nanoseconds by means of generating the same frequency of IF signal and modulating radio frequency(RF) signal. We adopt the limiting amplifier for the purpose of protecting the circuit from spurious signals which come from the front end side having wide instantaneous bandwidth characteristics and constantly injecting same level into the input local signal of IRM. The IRM we fabricated has image rejection ratio of 27dB, which is good over 7dB for foreign company's. Also, the SSB up-converter we fabricated has 1dB compression point of 18dBm, which is good over 16dB for foreign company's. And the size is compact about one-forth.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.3
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• pp.365-371
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• 2019

Recently, the demonstration and research on the power transmission using high voltage DC such as HVDC(High Voltage DC), Smart Grid, DC transmission and distribution have been actively conducted. In order to control the power converter in high-voltage DC power transmission system, SMPS(Switching Modulation Power Supply) for power converter control using high-voltage DC input is essential. However, the demand for high-pressure SMPS is still low, so the development is not enough. In the low-output SMPS using the high-voltage input, it is difficult to achieve high efficiency due to the switching transient loss especially at light load. In this paper, we propose a new switching scheme for high power SMPS control for low output power. The proposed method can provide better efficiency increase effect in the light load region compared to the existing PWM method. To verify the feasibility of the proposed method, a 40 W SMPS for HVDC MMC(Modulation Multi-level Converter) was designed and verified by simulation.