• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.200-204
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• 2001

A ZVZCS(Zero Voltage and Zero Current Switching) Three Level DC/DC Converter is presented to secondary auxiliary circuit. The new converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. A secondary auxiliary circuit, which consists of one small capacitor two small diode and one coupled inductor is added in the secondary to provides ZVZCS conditions to primary switches, ZVS for outer switches and ZCS for inner switches. Many advantages including simple circuit topology high efficiency, and low cost make the new converter attractive for high power applications. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 1kW 50kHz IGBT based experimental circuit.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.333-334
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• 2015

본 논문은 단상 플라잉 커패시터 멀티레벨 인버터에서의 스위칭 상태 변화 횟수를 줄이는 새로운 기법을 제안하였다. 제안한 방법은 플라잉 커패시터 멀티레벨 인버터가 갖는 Redundant state 특성을 이용하며, 플라잉 커패시터 전압이 제어되는 범위 내에서 각 스위치가 최대한 적게 온/오프 하도록 Redundant state를 선택한다. 이를 단상 3-레벨 플라잉 커패시터 인버터에 적용하여 ＰＳＩＭ 시뮬레이션을 통해 유효성을 검증하였다.

• 전력전자학회논문지
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• 제26권2호
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• pp.82-89
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• 2021

This study proposes a DAB two-stage series structure with insulated bidirectional DC-DC converter for two-way power transfer between the renewable energy of high voltages (1 kV and above). The proposed circuit transforms the existing DAB converter into a two-stage series structure to reduce the pressure in the switch. The problem of power imbalance occurring in the design of the DAB converter second-stage series is improved by applying the cell balancing method circuit and the common mode coupled inductor using an external flying capacitor instead of reflecting the existing improvement measures, voltage balance control, and inductor current control. In addition, a no-load supercharging sequence is proposed in high voltages and high-speed switching by using the fixed duty output method. This study presents the analysis results through the structure of the proposed circuit, the principle of improving the power imbalance problem, and simulations. Prototypes were manufactured to meet the specifications of input/output voltage of 1700 V, maximum load of 65 kW, and switching frequency of 51kHz, and the validity of the topology was verified using the experimental results and efficiency data.

• Journal of Power Electronics
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• 제15권5호
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• pp.1190-1199
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• 2015

This paper presents a new resonant converter to achieve the soft switching of power devices. Two full-bridge converters are connected in series to clamp the voltage stress of power switches at V_in/2. Thus, power MOSFETs with a 500V voltage rating can be used for 800V input voltage applications. Two flying capacitors are connected on the AC side of the two full-bridge converters to automatically balance the two split input capacitor voltages in every switching cycle. Two resonant tanks are used in the proposed converter to share the load current and to reduce the current stress of the passive and active components. If the switching frequency is less than the series resonant frequency of the resonant tanks, the power MOSFETs can be turned on under zero voltage switching, and the rectifier diodes can be turned off under zero current switching. The switching losses on the power MOSFETs are reduced and the reverse recovery loss is improved. Experiments with a 1.5kW prototype are provided to demonstrate the performance of the proposed converter.

• 한국철도학회논문집
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• 제19권3호
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• pp.297-303
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• 2016

본 논문은 철도차량에 사용되는 보조전원장치(APS)의 고효율화 및 경량화를 위한 방안으로 새로운 철도차량용 보조전원장치의 회로 구조를 제안한다. 제안하는 회로 구조는 기존의 보조전원장치 전력변환 흐름에서 중복 수행되고 있는 전력변환 단계를 단순화 하여, 스위치 소자의 부담을 경감하고 수동소자의 크기를 줄여 전력밀도를 높이는 것을 목적으로 하고 있다. 본 연구에서 제안하는 회로 구조는 기존 철도차량용 보조전원장치에 널리 이용되는 멀티레벨 컨버터를 기본 회로로 하고 있으며, 기존 회로의 1차 측 구조에 커패시터 소자를 추가하여 전력변환 스위치의 소프트스위칭 조건을 용이하게 하는 효과를 얻음과 동시에 추가되는 커패시터를 별도의 저전압 전원소스로 활용하고자 한다. 판토그래프 단에 위치하는 새로운 전원소스를 활용하여 철도차량에 탑재되는 배터리 충전용 컨버터의 에너지를 직접 공급받음으로써, 기존 주 전력변환 컨버터 용량 및 사이즈가 절감되는 효과를 얻을 수 있을 뿐만 아니라 전력변환 단계의 축소로 에너지 변환 효율도 향상되는 효과를 얻을 수 있다. 본 연구에서는 도시철도차량에서 사용되는 보조전원장치의 스펙을 적용하여 제안하는 회로를 디자인하고 타당성을 검증하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권4호
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• pp.451-462
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• 2016

Photovoltaic energy conversion becomes main focus of many researches due to its promising potential as source for future electricity and has many advantages than the other alternative energy sources like wind, solar, ocean, biomass, geothermal etc. In Photovoltaic power generation multilevel inverters play a vital role in power conversion. The three different topologies, diode-clamped (neutral-point clamped) inverter, capacitor-clamped (flying capacitor) inverter and cascaded h-bridge multilevel inverter are widely used in these multilevel inverters. Among the three topologies, cascaded h-bridge multilevel inverter is more suitable for photovoltaic applications since each pv array can act as a separate dc source for each h-bridge module. This paper presents a single phase Cascaded H-bridge five level inverter for grid-connected photovoltaic application using sinusoidal pulse width modulation technique. This inverter output voltage waveform reduces the harmonics in the generated current and the filtering effort at the input. The control strategy allows the independent control of each dc-link voltages and tracks the maximum power point of PV strings. This topology can inject to the grid sinusoidal input currents with unity power factor and achieves low harmonic distortion. A PID control algorithm is implemented in Arm Processor LPC2148. The validity of the proposed inverter is verified through simulation and is implemented in a single phase 100W prototype. The results of hardware are compared with simulation results. The proposed system offers improved performance over conventional three level inverter in terms of THD.

• 전기학회논문지
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• 제57권6호
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• pp.972-981
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• 2008

A New ZVS(Zero Voltage Switching) and ZVZCS(Zero Voltage and Zero Current Switching) Three-Level Converter is proposed. The proposed converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the all switch. A primary auxiliary circuit, which consists of one coupled inductor, is added in the primary to provide ZVZCS conditions to primary switches. Many advantages including simple circuit topology high efficiency, and low cost make this converter attractive for high power applications. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 2kW(27V, 74A) 40 kHz IGBT based experimental circuit.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.227-231
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• 2001

A new primary-side-assisted zero-voltage and zero-current switching (ZVZCS) three-level DC-DC converter with flying capacitor is proposed. The three-level converters are promising in high voltage applications, and ZVZCS is a very effective means for reducing switching losses. The proposed DC-DC converter uses only one auxiliary transformer and two diodes to obtain ZCS for the inner leg. It has a simple and robust structure, and offers soft-switching capability even in short-switching conditions. The proposed converter was verified by experiments in a 6KW prototype designed for communication applications and operating at 100kHz.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.187-193
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• 2007

This paper presents the Efficiency Characteristic of Three-Level Converter. Three-Level DC/DC Converter Presented in this paper is used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. This converter reduces the voltage stress across the main switch to half of input voltage. This paper analyses the loss of each component and the various losses for efficiency variation. The result of the analysis are verified using 3kW prototype.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 추계학술대회 논문집
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• pp.119-120
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• 2014

멀티레벨 인버터는 낮은 고조파 성분을 갖고, 제한된 정격 스위칭 소자로 대용량 전력변환이 요구되는 시스템에 매우 효율적이다. 수학적인 해석방법을 통해 전도손실, 스위칭 손실, 출력 전압 전류의 THD의 해석방법을 제시하고 시뮬레이션을 통해 멀티레벨 인버터의 특성을 비교 분석을 한다. 본 논문은 기존 제안된 멀티레벨 구조인 NPC(Neutral Point Clamped) 멀티레벨 인버터, Cascaded H-bridge 멀티레벨 인버터, Flying capacitor 멀티레벨인버터를 기반으로 25MW급 대용량 인버터의 손실 및 출력특성을 비교 분석하였다.