• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.317-319
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• 2019

In this paper, a three level duty cycle controlled half bridge LLC converter for EV charger application is presented. The topology and operating regions of the converter are discussed. The equations of the converter are derived in time domain. A small signal model of the converter is developed by perturbation and linearization of the steady state model about their operating point using Extended Describing function.

• 전력전자학회논문지
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• 제26권3호
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• pp.227-236
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• 2021

This research proposes a modeling and controller design of a three-level boost (TLB) converter for the implementation of maximum power point tracking (MPPT) in the photovoltaic power conditioning system (PCS). Contrary to the output voltage control of the conventional controller, the Photovoltaic PCS requires an input voltage controller for MPPT operation. A TLB converter has the advantage of decreasing the inductor size and increasing efficiency compared with the existing booster converter. However, an optimal controller is difficult to design due to the complexity of the TLB operations, which have two operational modes on the duty ratio boundary of 0.5. Therefore, the unified linear model equations of the TLB converters, which can be applicable to both operational modes, are derived using linearized solar cell expressions. Furthermore, the transfer functions are obtained for the controller design. The MPPT voltage controller is designed using MATLAB SISOTOOL. In addition, a controller for capacitor voltage unbalancing is described and designed. The simulations and experimental verifications are conducted to verify the effectiveness of the small-signal analysis and control system design.

• 전력전자학회논문지
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• 제6권2호
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• pp.209-216
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• 2001

종래의 위상전이 영저낮 스위칭 풀-브리지 DC/DC 컨버터와 비슷하게 영전압 스위칭 3레벨 DC/DC 컨버터의 동작 모드 및 파형에서도 순환모드 구간동안 흐르는 순환전류에 EK라 스위칭소자 및 변압기에서의 도통손실이 증가하는 단점을 갖고 있다. 따라서, 본 논문에서는 스위칭전원의 효율개선 및 스위칭 주파수를 증가시키기 위한 보다 개선되고, 진보된 탭인덕터와 스너버 캐패시터/다이오드로 구성된 2차 측 보조회로 적용 영전압 $\cdot$영전류 스위칭 3 레벨(Level) DC/DC컨버터에 대한 주 회로특성분석 및 7kW, 30kHz DC/DC 컨버터의 시제품을 제작하여 실험한 결과에 대해 서술하고자 한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.434-435
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• 2018

In this paper, a single-phase single-stage three-level AC/DC converter with a wide controllable output voltage is presented. It integrates a PFC converter and a three level DC/DC converter into one. The proposed converter operates at a fixed frequency and provides a wide controllable output voltage ($200V_{dc}-430V_{dc}$) with high efficiencies over a wide load range. In addition, the input boost inductors operate in a discontinuous mode to improve the input power factor. Moreover, all the switching devices operate with ZVS, and the converter's THD is small especially at full load. The feasibility of the proposed converter is verified with experimental results of a 1.5kW prototype.

• 전력전자학회논문지
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• 제15권6호
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• pp.451-459
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• 2010

본 논문은 대규모 풍력단지를 교류 전력망에 연계하기 위한 3-레벨 PWM 컨버터와 3-레벨 24-펄스 컨버터로 구성된 하이브리드 Back-to-Back 컨버터의 성능을 비교한 결과에 대해 기술하고 있다. 또한 3-레벨 24-펄스 컨버터를 점호각만 제어하는 경우와 영 전압제어를 같이 수행하는 경우 각각이 제어와 고조파레벨에 미치는 영향을 비교 분석하였다. 구체적인 성능비교를 위해 먼저 PSCAD/EMTDC 소프트웨어를 사용하여 시뮬레이션을 실시하고 이를 바탕으로 2 kVA 용량의 하드웨어 축소모형을 제작하고 실험을 실시하였다. 시뮬레이션과 실험을 통해 영전압과 점호각을 동시에 조절하는 방식과 점호각만 제어하는 방식의 성능비교분석을 하였다.

• 전력전자학회논문지
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• 제24권6호
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• pp.406-410
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• 2019

Three-level (3L) DC-DC converters are appropriate for high-input-voltage applications. Although the voltage stress of TL converter switches can be reduced to half of the input voltage, the primary side has a large circulating current, which degrades efficiency. In this study, a dual half-bridge cascaded TL converter is presented to reduce this circulating current and thus decrease the conduction loss of the primary circuit. Moreover, the proposed converter can reduce the voltage stress of rectifier diodes, thereby reducing their conduction loss. Therefore, efficiency can be improved by reducing the conduction loss of the primary circuit and rectifier diodes.

• 전력전자학회논문지
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• 제25권4호
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• pp.269-278
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• 2020

In this paper, two types of DC/DC converters in a hydrogen fuel cell hybrid railway vehicle system, which serve to charge high-voltage battery and supply power to an inverter for driving a driving motor, were compared and analyzed. A two-level interleaving boost converter and a three-level boost converter were compared and analyzed, and a theoretical design method was proposed to have an efficiency characteristic of over 95%. In addition, a digital controller design method considering the digital phase delay component of DSP (TMS320F28335) is presented. Finally, the validity of the theoretical design of the converter with 20kW power was verified through static and dynamic experiments respectively.

• 전력전자학회논문지
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• 제12권3호
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• pp.205-212
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• 2007

본 논문에서는 토오크 맥동을 줄이고 동특성 및 효율을 개선하기 위해 새로운 4-레벨 콘버터 이용한 DITC SRM 구동방식을 제안하였다. 4-레벨 콘버터는 콘덴서의 전압을 이용하여 여자 및 감자 시 높은 전압을 인가하여 여자특성을 개선할 수 있는 장점을 가진다. 본 논문에서는 DITC의 동특성 개선을 위해 사용된 4-레벨 콘버터의 동작특성과 부스트 전압에 따른 효율 개선에 대해 해석하였다. 이를 통해 제안된 SRM을 위한 4-레벨 콘버터의 DITC 제어기법을 시뮬레이션과 실험을 통해 검증하였다.

• Journal of Power Electronics
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• 제8권3호
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• pp.248-258
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• 2008

The Voltage Source Converter (VSC) is replacing the conventional line commutated current source converters in High Voltage DC (HVDC) transmission systems. The control of a two-level voltage source converter and its design dealt with HVDC systems and various factors such as reactive power, power factor, and harmonics distortion are discussed in detail. Simulation results are given for the two-level converter and designed control is used for bidirectional power flow. The harmonics minimization is taken by extending the 6-pulse VSC to multipulse voltage source converters. The control is also tested and simulated for a 12-pulse voltage source converter to minimize the harmonic distortion in AC currents.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권12호
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• pp.682-690
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• 2002

The conventional three-level high frequency phase-shifted dc/dc converter has a disadvantage that a circulating current flows through transformer and switching devices during the freewheeling interval.. Due to this circulating current and RMS current stress, conduction losses of transformer and switching devices increases. To alleviate these problems, we propose an improved three-level Zero Voltage and Zero Current Switching (ZVZCS) dc/dc converter using a tapped inductor, a snubber capacitor and two snubber diodes attached at the secondary side of transformer. The proposed ZVZCS converter is verified on a 7㎾, 30KHz experimental prototype.