• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.6
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• pp.529-534
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• 2017

In this paper, the implementation of proposed Automatic Load Balanced (ALB) PWM generation method is discussed. The conventional PWM generation method for cascade type H-bridge PWM converter causes the unbalance between each H-bridge converter, therefore the complex redundancy is required for the balancing of switching load of each converter, it consumes more computing power of controller. The ALB PWM method needs no additional switching redundancy for balancing, this paper discusses the implementation of ALB-PWM.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.2
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• pp.95-101
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• 2017

A simple and practical voltage balance method for a solid-state transformer (SST) is proposed to reduce the voltage difference of cascaded H-bridge converters. The tolerance device components in SST cause the imbalance problem of DC-link voltage in the H-bridge converter. The Max/Min algorithms of voltage balance controller are merged in the controller of an AC/DC rectifier to reduce the voltage difference. The DC-link voltage through each H-bridge converter can be balanced with the proposed control methods. The design and performance of the proposed SST are verified by experimental results using a 30 kW prototype.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.136-145
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• 2009

This paper proposes control methods and simulation models of a driving system, which consists of converters and inverters, for high speed trains employing multi-level power converters. The control method of a single phase three-level converter for high-speed trains is designed to use DC values instead of instantaneous current values which are usually used in single-phase application, so that it results in a fast and robust voltage control response. In addition, simulation models of Space Vector Pulse Width Modulation (SVPWM) for single phase three-level converters as well as three level inverters are proposed. Experimental results demonstrate the validity of the simulation model for three-level inverters.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.105-107
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• 2018

This paper presents a new hybrid multilevel converter topology, which consists of a combination of the series connected switched capacitor units with boost ability, and an H-bridge with T-type bidirectional switches. The proposed converter boosts the input voltage without any bulky inductors, and has the small number of components, which can make the size and cost of a power converter greatly reduced. The output filter size and harmonics are also reduced by the high quality multilevel output. In addition, there is no need for complicated methods to balance the capacitor voltage. Simulation and experimental results with a nine-level converter system are presented to validate the proposed topology and modulation method.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.343-346
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• 2000

In most inverter/converter applications SVPWM method is the preferred approach for it shows good characteristics in linear modulation range and waveform quality. in this paper we propose a new carrier based SVPWM method for multi-level system. First we survey the conventional carrier based SVPWM method and investigate the problem of the conventional one for the multi-level system with the focus on the switching frequency harmonic flux trajectories. Finally we propose a new carrier based SVPWM method that can reduce harmonic distortion. Simulation and experimental results are given for the verification of the proposed SVPWM method.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.529-533
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• 2001

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.59-60
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• 2015

본 논문에서는 직류송전 적용을 위해 전력계통과 연계된 모듈형 멀터레벨 컨버터(Modular Multi-level Converter)의 유 무효 전력제어에 대해 시뮬레이션 모델을 개발하고 그 특성을 분석하였다. 분석에 고려한 모듈형 멀티레벨 컨버터는 한 암당 12개의 서브모듈로 구성되어 있고 모듈레이션은 NLC (Nearest Level Control) 방식을 사용한다. 또한 DC 커패시터의 밸런싱은 버블소팅 방식을 적용하였고 순환전류를 억제하는 알고리즘을 고려하였다. 시뮬레이션을 통해 분석한 유 무효전류제어를 실험적으로 검증하기 위해 10kVA DC 1000V 하드웨어 축소모형을 제작하고 실험을 실시하였다. 실험결과는 시뮬레이션 결과와 일치함을 확인할 수 있었다. 향후에는 교류전압 불평형 보상과 순환전류 제어, 컨버터 보호에 대한 다양한 알고리즘을 도출할 예정이다.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1093-1099
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• 2014

This paper proposes a power conversion topology involving a multi-winding transformer and converters. The fundamental idea is described with circuit diagrams, and the voltage output of the proposed topology is analyzed mathematically. The effectiveness of the topology is discussed with test results from a small-scale power conversion system. When conventional hardware consisting of two-level converters and a transformer is employed, multi-level voltage outputs can be applied to the transformer windings by the proposed method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3079-3085
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• 2014

This paper suggests a power level controllable frequency up-converter which is designed and fabricated using both the filtering technology consisted with only passive devices and a multi-level digital attenuator. The suggested frequency up-converter simultaneously realizes the low power consumption and the low cost model. Because of the possibility for controlling power levels, it is possible to use the suggested frequency up-converter for wide spectral range. According to the experimental results, the average gain value of 0.75dB is obtained for the bandwidth of 160MHz at the center frequency of 1,200MHz. Especially, it is confirmed that the power level can be controlled from 10 to -21.5dBm through the digital attenuator.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.12
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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.