• 전력전자학회논문지
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• 제21권4호
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• pp.328-334
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• 2016

This paper examines the reliability of a VSC-HVDC valve based on a modular multilevel converter (MMC) HVDC system. The main objective of this paper is to determine the redundancy of the MMC valve. Several prediction methods are introduced, but the binomial failure method is selected to be used. To determine the availability and reliability prediction of MMC valve, which comprises a DC/DC converter, a gate driver, a capacitor, and an IGBT, the failure data of the MMC module are used as the tracking data according to the experimental result. This method uses a simplified equation to find the valve redundancy by transforming the binomial function to De Moivre's formula. This method is the first to be used to find the valve margin.

• 전기학회논문지
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• 제63권12호
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• pp.1640-1648
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• 2014

This paper proposes a switching frequency reduction method for MMC (Modular Multilevel Converter) utilizing redundancy operation of sub-module, which can offer reduction of voltage harmonics and switching loss. The feasibility of proposed method was verified through computer simulations with PSCAD/EMTDC software. Based on simulation analysis, a hardware scaled-model of 10kVA, DC-1000V MMC was designed and manufactured in the lab. Various experiments were conducted to verify the feasibility of proposed method in the actual hardware system. The hardware scaled-model can be effectively utilized for analyzing the performance of MMC according to the modulation scheme and redundancy operation.

• 한국정보전자통신기술학회논문지
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• 제10권6호
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• pp.529-534
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• 2017

본 논문에서는 스마트그리드의 핵심 설비 중 하나인 반도체 응용 고주파 변압의 개발을 위한 PWM 컨버터의 PWM 생성 방식과 그 구현에 관한 논문으로, H-bridge의 cascade 방식으로 구성된 PWM 컨버터의 경우 각 H-bridge간의 전압 balancing이 항상 이슈로 대두되는 바, 이러한 불균형은 대부분의 경우 각 H-bridge에 부가되는 스위칭 부하가 각각 균형적으로 분포되는 것이 불가능하기 때문에 발생하는 것으로 이를 해결하기 위해 종래의 경우 스위칭 패턴에 복잡한 리던던시를 추가하여 해결 하였으나, 본 논문에서 적용하는 방법은 이러한 리던던시가 불필요해 제어기의 부담을 저감할 수 있다. 본 논문에서는 이러한 자동부하분담 PWM 방식(ALB-PWM)의 실 구현에 관하여 논하였다.

• 전기학회논문지
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• 제62권9호
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• pp.1240-1248
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• 2013

This paper describes a switching-level operation analysis of BTB(Back-To-Back) converter for HVDC(high voltage DC) application based on MMC(modular multi-level converter). A switching-level operation analysis for BTB converter is very important to understand the converter operation in detail and check the voltage and current transients in each components. However, the development of switching-level simulation model for the actual size BTB Converter is very difficult because the MMC normally has more than 150 sub-modules for each arm. So, a switching level simulation model for the 11-level MMC-based BTB converter was developed with PSCAD/EMTDC software, which has 12 sub-modules for the positive arm and another 12 sub-modules for the negative arm. The DC-voltage balance algorithm, the circulating-current reduction algorithm, the harmonic reduction algorithm, and the redundancy operation algorithm were included in this simulation model. The developed simulation model can be utilized to analyze the MMC-based BTB converter for HVDC application in switching level and to develop the protection scheme for the MMC-based BTB converter for HVDC application.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 추계학술대회 논문집
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• pp.11-12
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• 2014

This paper introduces a scaled hardware model for the 10kVA, 1kV, 11-level MMC (Modular Multilevel Converter), which was manufactured in the lab based on computer simulations with PSCAD/EMTDC. Various experiments were conducted to verify the major operation algorithms of MMC. The hardware scaled-model developed in the lab can be utilized for analyzing the operation analysis and performance evaluation of MMC according to the modulation pattern and redundancy operation scheme.

• Journal of Power Electronics
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• 제10권1호
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• pp.34-42
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• 2010

Reliability is an important issue in cascaded H-bridge converters (CHB converters) because they use a high number of power semiconductors. A faulty power cell in a CHB converter can potentially lead to expensive downtime and great losses on the consumer side. With a fault-tolerant control strategy, operation can continue with the undamaged cells; thus increasing the reliability of the system. In this paper, the operating principles and the control method for a CHB multilevel rectifier are introduced. The influence of various faults on the CHB converter is investigated. The method of fault diagnosis and the bypassing of failed cells are explained. A fault-tolerant protection strategy is proposed to achieve redundancy in the CHB rectifier. The redundant H-bridge concept helps to deal with device failures and to increase system reliability. Simulation results verify the performance of the proposed strategy.

• 전기학회논문지
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• 제63권8호
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• pp.1046-1054
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• 2014

In this paper, a hardware prototype for the 10kVA 11-level MMC was built and various experimental works were conducted to verify the operation algorithms of MMC. The hardware prototype was designed using computer simulation with PSCAD/EMTDC software. After manufactured in the lab, the hardware prototype was tested to verify the modulation algorithms to form the output voltage, the balancing algorithm to equalize the sub-module capacitor voltage, and the redundancy operation algorithm to improve the system reliability. The developed hardware prototype can be utilized for analyzing the basic operation and performance improvement of MMC according to the modulation and redundancy operation scheme. It also can be utilize to analyze the basic operational characteristics of HVDC system based on MMC.

• 한국정보전자통신기술학회논문지
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• 제6권3호
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• pp.135-140
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• 2013

본 논문은 스마트 그리드의 핵심 설비중 하나인 반도체 지능형 변압기의 시스템 구성과 이에 필요한 PWM 컨버터의 PWM 생성 방식에 관한 논문으로, 반도체 지능형 변압기의 경우 입력단이 수전계통에 직접 접속되기 때문에 고전압을 견딜 수 있는 방식으로 구성되어야 하고 이를 위해서는 다단 연결방식의 PWM 컨버터의 구성이 필수적이다. 종래의 PWM 생성 방식의 경우 지령전압의 크기에 따라서 각 단별 스위칭 부하가 균등하게 분포되지 않기 때문에 이를 해결하기 위한 복잡한 리던던시를 스위칭 패턴에 추가해야 했으나, 본 논문에서 제안하는 방식의 경우 부하의 분담이 자동적으로 이루어지기 때문에 그러한 부담없이 시스템을 구성하는 것이 가능하다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2002년도 학술대회논문집
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• pp.157-163
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• 2002

Consideration for parallel operation in a high power system has been increased due to the advantages of parallel operation like as high productivity, simplicity of design, and redundancy of power. This paper discussed the parallel operation of DC-DC Converter, Which Can be used as a high power system, is studied. Based on the small signal model of DC-DC Converter, the simple and exact power stage model of parallel operation system is derived and the parallel operation system using current balance method for the uniform current distribution among the parallel operation system is discussed. To verify the high performance of the proposed DC-DC converter system for parallel operation, the simulation test of the parallel operation, which has 2 Converter modules, is accomplished.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.540-541
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• 2013

본 논문에서는 PSCAD/EMTDC를 이용하여 MMC(Modular Multi-level Converter)를 기반으로 한 HVDC 시스템 시뮬레이션 모델을 개발하였다. 스위칭 레벨의 동작을 분석하기 위해 각 ARM당 10개의 SM(Sub-Module)과 2개의 RM(Redundancy-Module)을 구성하여 11-level의 MMC 출력 전압을 형성하였다. SM 동작시 발생하는 전압 불균등 문제를 해결하기 위하여 밸런싱 알고리즘을 적용하였으며, SM의 출력 전압에 발생하는 Ripple을 고려하여 Capacitor의 용량을 설계하고 이를 검증하였다. 또한 시뮬레이션을 이용하여 HVDC 성능 분석과 MMC의 성능개선을 위한 순환전류 알고리즘 및 Redundancy 투입 알고리즘을 구현하고 그 결과를 확인하였다.