• Journal of Power Electronics
• /
• v.14 no.3
• /
• pp.499-506
• /
• 2014

This paper proposes a 3 kW single-phase bi-directional multi-level converter for energy storage applications. The proposed topology is based on the H-bridge structure with four switches connected to the DC-link. A simple phase opposition disposition PWM method that requires only one carrier signal is also suggested. The switching sequence to balance the capacitor voltage is considered. The topology can be extended to a nine-level converter or a three-phase system. The operating principle of the proposed converter is verified through a simulation and an experiment.

• Proceedings of the KIPE Conference
• /
• 2001.07a
• /
• pp.215-218
• /
• 2001

This paper is proposed a sinusoidal input current multi-level ac-dc converter using transformer. The multi-level converter which controls input current by combining Buck converter to Improve input current characteristics. This method, which is multiplying and duplicating output of converter of equal capacity, is able to control unit power factor of input current, reduce the problem caused by high frequency switching, and apply to high power converter because filter is not necessary The feasibility of the circuit is verified by computer simulation using PSIM

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.11
• /
• pp.2015-2021
• /
• 2008

Recently, with the growth of photovoltaic system, many researchers and companies have concerned about the multi-level inverter which has an efficiency of boosting voltage. In this paper a novel structure of multi-level converter for reducing ripple of output voltage is proposed. In the proposed converter Buck converters are connected in series to generate the output voltage and the ripple of output voltage can be reduced compared with the exiting Buck converter. Especially when outputting lower output voltage the number of acting switching elements is less and the result of ripple reducing is more obvious. This paper implements a multi-level switching function based on the FPGA.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.1
• /
• pp.333-344
• /
• 2018

This proposed paper aims for the high efficiency contactless power transfer in household dc power distribution. A 300 W five-level diode clamped multi-level converter with 300 Vdc input dc link bus is employed for the power transferring task and the output voltage range is controlled at 48 Vdc. The inner and outer solenoid coils are used for inductive power transfer (IPT) transformer with the 200 kHz switching frequency for designed power density. Therefore, to achieve the converter efficiency above 95%, the LLC series resonant with fundamental harmonic analysis (FHA) and the calculated switching angles are used as an optimized tool for designing the system resonant tank. The validations of this approached topology are illustrated in both MATLAB/Simulink simulation and implementation.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.3
• /
• pp.274-284
• /
• 2003

Multi-level converter that is high-capacity electric power conversion system is used widely to electric motor drive system and FATCs(Flexible AC Transmission Systems). H-Bridge converter has been prevalently applied to shunt-type system because it can be easily expanded to the multi-level. In steady states, converter is normally operated in the range of 0.7∼0.8 of modulation Index. Even though zero vectors are not imposed to high modulation index, DC-Link voltage Is constant. It means that converter has another boost vector except for zero vectors among several vectors in 3-level converter. This paper has examined the principle of boost vector and investigated the difference between another boost vector and zero vectors in 3-level converter. In addition, this paper has analysed and compared the charging currents and the capacitor voltages of two topologies. The currents and voltages are related to reference voltage. Therefore, it proposed the calculation method for the voltage ripple and the charging current of each capacitor and compared various DC-Link voltage control methods through the simulation.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.9
• /
• pp.1240-1248
• /
• 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.

• Proceedings of the KIPE Conference
• /
• 2012.07a
• /
• pp.351-352
• /
• 2012

본 논문에서는 최근 직류송전용 컨버터로 많은 관심이 집중되고 있는 MMC(Modular Multi-level Converter)에 대해서 소개하고 있다. 대용량 전압원 컨버터로 MMC가 적합한 이유에 대해서 설명하고, MMC의 동작원리, SM(Sub-Module) dc capacitor voltage balancing 기술, 전체 제어 시스템에 대해 자세하게 설명하고 있다. 제안하는 MMC는 Staircase Modulation 방식으로 사인파형에 가까운 출력전압을 형성하고, Sorting 알고리즘을 구현하여 개별 SM의 커패시터 전압이 균등하게 일정 값을 유지하도록 하였다. 제안하는 MMC의 성능평가를 위하여 PSCAD/EMTDC 프로그램을 이용하여 3상 11-level MMC를 모의하였다.

• Journal of Power Electronics
• /
• v.9 no.3
• /
• pp.396-402
• /
• 2009

A DC/DC converter generally needs to work under high switching frequency when used as an adjustable power supply to reduce the size of magnetic elements such as inductors, transformers and capacitors, but with the rising of the switch frequency, the switch losses will increase and the efficiency will reduce. Recently, to solve these problems, research is actively being done on a soft switching method that can be applied under high frequency and on a PWM converter that can be applied under low frequency such as a multi-level topology. In this paper a novel DC-DC conversion method for reducing the ripple of output voltage is proposed. In the proposed converter, buck converters are connected in series to generate the output voltage. By using this method, the ripple of output voltage can be reduced compared to a conventional buck converter. Particularly when output voltage is low, the number of acting switching elements is less and the result of ripple reduction is more obvious. It is expected that the converter proposed in this paper could be very useful in the case of wide-range output voltage.

• Proceedings of the KIPE Conference
• /
• 2016.07a
• /
• pp.129-130
• /
• 2016

본 논문에서는 근사 계단 제어 변조(Nearest Level Control Modulation)로 동작하는 모듈형 멀티레벨 컨버터(Modular Multi level Converter)에서 충전 회로나 반송파(Carrier)없이 초기 충전(Pre-charging)하는 새로운 방식을 제안하였다. 이의 성능을 검증하기 위해 PSCAD/EMTDC 소프트웨어를 통해 암(Arm)당 12개의 서브모듈(Sub-Module)로 구성된 3상 10kVA 모듈형 멀티레벨 컨버터를 구현 및 시뮬레이션을 수행하였다.

• Proceedings of the KIPE Conference
• /
• 2011.11a
• /
• pp.67-68
• /
• 2011

본 논문에서는 Modular Multi-Level Converter(MMLC)의 셀(Cell) 캐패시터(Capacitor) 전압 밸런싱에서 전압맥동 최소화 방법을 제안한다. 암(Arm) 평균 전류를 직류성분으로만 제어 할 경우 기본파 주파수와 2 고조파로 흔들리는 순시전력 항이 셀 캐패시터 전압 맥동을 만든다. 이를 억제 하기위해 암 평균 전류에 2 고조파 교류 성분을 직류성분과 함께 제어하는 방법을 제안한다. 이 방법을 통하여 전압맥동을 줄일 수 있음을 밝히고, 주입되는 2 고조파 전류의 크기와 위상각 계산 방법을 제시한다. 모의실험 결과를 통해 제안된 방법의 유효성을 검증하였다.