• 전력전자학회논문지
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• 제24권6호
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• pp.459-462
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• 2019

This work presents methods for reducing overshoot voltages across the drain-source of silicon carbide (SiC) MOSFETs in grid-connected hybrid active neutral-point-clamped (ANPC) inverters. Compared with 3-level NPC-type inverter, the hybrid ANPC inverter can realize the high efficiency. However, SiC MOSFETs conduct its switching operation at high frequencies, which cause high overshoot voltages in such devices. These overshoot voltages should be reduced because they may damage switching devices and result in electromagnetic interference (EMI). Two major strategies are used to reduce the overshoot voltages, namely, adjusting the gate resistor and using a snubber capacitor. In this paper, advantages and disadvantages of these methods will be discussed. The effectiveness of these strategies is verified by experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.409-412
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• 2006

EEFL can be driven by square wave driving method. A square wave is applied directly to both ends of EEFL by cascaded multi-stage full-bridge inverter. The various current shapes of lamp are achieved by various inductors between lamp and inverter. In this paper, it is newly investigated that the area of current directly influences the luminance. Furthermore, the 3-level square wave is considered to drive EEFL with self-discharge characteristics. The highest luminance efficiency is achieved by properly controlling the rate of self-discharge usage.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 추계학술대회
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• pp.105-106
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• 2017

본 논문은 10kW급 태양광 3 레벨 NPC 인버터 설계에 대해 서술하였다. 3 레벨 인버터는 2 레벨 인버터보다 정격 전압과 출력전류의 고조파 감소가 가능하기 때문에 효율이 높다는 장점이 있다. 설계된 태양광 3 레벨 인버터는 제어보드, 게이트보드, 3 레벨 IGBT 등으로 구성된다. 게이트 드라이버 보드는 소자들의 최소 절연거리와 신호전달의 용이성을 고려하여 설계되었다. 3 레벨 NPC 인버터의 동작을 PSIM을 통해 시뮬레이션 하였으며, 실험을 통하여 제작된 태양광 3 레벨 인버터가 실제 조건에서도 정상적으로 동작함을 검증하였다.

• 전기학회논문지
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• 제67권2호
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• pp.233-238
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• 2018

This paper proposes a seamless MPPT operation mode transfer method of photovoltaic system. The photovoltaic system consists of a DC-DC boost converter, a DC-Link, and a 3-level neutral point clamp (NPC) type inverter. The PV voltage fluctuates due to the output characteristics of the solar pane1 depending on the irradiation amount and the temperature. The photovoltaic system requires seamless MPPT mode transfer method that the discontinuity does not occur in order to supply the stable power to system without affecting the fluctuation of the PV voltage. MPPT operation is divided into two modes by the voltage reference. Under the condition that the PV voltage is below 650V, the DC-DC boost converter performs MPPT through duty control based on perturb & observe (P&O) method, and the inverter conducts DC-link voltage and grid current controls in synchronous reference frame. On the other hand, when the PV voltage exceeds above 650V, inverter performs MPPT in accordance with the variation of DC-link voltage control while the converter stops operating. Two MPPT operation modes is smoothly transferred through the proposed method that DC-link voltage or grid current commands are appropriately adjusted from the certain criteria. The feasibility of the MPPT operation mode transfer method is verified using a 10kW solar photovoltaic system, experimental results have good performances that the fluctuation of PV current is reduced to 100%.

• 전기학회논문지
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• 제56권3호
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• pp.457-464
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• 2007

Micro-Grid comprising Micro-Sources supplying several $kW{\sim}MW$ power to local customers is environmentally friendly and reliable. This paper deals with the development of simulation models of Micro-Grid on the PSCAD/EMTDC platform for analyzing various aspects of the interaction of the Micro-Grid. The developed switching level model adopts the space vector PWM. Both switching level and power frequency Micro-Source models are developed, which shows that power frequency modeling is sufficient for analyzing the phenomena of interest. Control characteristics of the Micro-Sources with the parameter and load power variation are analyzed for power quality enhancement. The simulation results show that the developed models are effective for studying Micro-Grid.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.41-42
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• 2015

본 논문에서는 보조회로 및 양방향 컨버터를 추가한 H-bridge 모듈 3개를 직렬 결합하여 7레벨과 27레벨의 선택적 출력전압 생성이 가능한 멀티레벨 인버터 구조를 제안한다. 제안된 회로의 입력전압원 크기는 서로 동일하며, 최초 7레벨의 출력전압을 생성하다가 양질의 출력전압을 필요로 할 경우 27레벨의 출력전압을 생성할 수 있으며, 7레벨 및 27레벨 출력전압에 대한 동작 특성을 해석하고 시뮬레이션을 통해 타당성을 검증한다.

• 한국전기전자재료학회논문지
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• 제29권9호
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• pp.523-526
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• 2016

This paper was researched about 1,200 V level floating island IGBT (insulated gate bipolar transistor). Presently, 1,200 V level IGBT is used in Inverter for distributed power generation. We analyzed and compared electrical charateristics of the proposed floating island IGBT and conventional IGBT. For analyzing and comparison, we used T-CAD tool and simulated the electrical charateristics of the devices. And we extracted optimal design and process parameter of the devices. As a result of experiments, we obtained 1,456 V and 1,459 V of breakdown voltages, respectively. And we obatined 4.06 V and 4.09 V of threshold voltages, respectively. On the other hand, on-state voltage drop of floating island IGBT was 3.75 V. but on-state vlotage drop of the conventional IGBT was 4.65 V. Therefore, we almost knew that the proposed floating island IGBT was superior than the conventional IGBT in terms of power dissipation.

• 전력전자학회논문지
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• 제27권3호
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• pp.221-227
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• 2022

The reliability improvement of PV systems is an important factor in reducing the cost of PV energy because it is closely related to the annual energy production as well as the maintenance cost of PV systems. The reliability of PV inverters plays a key role in the reliability of PV systems because it is regarded as one of the most reliable critical parts of PV systems. The lifetime evaluation of PV inverters considering the mission profile in the design phase plays an important role in reliability design to ensure the required lifetime of PV inverters. In this paper, the lifetime of representative single-phase T-type and I-type NPC inverters are comparatively evaluated by considering the mission profile of a PV system recorded at Iza, Spain. Furthermore, the effect of the pulse width modulation methods on the lifetime is also discussed. The lifetime evaluation of PV inverters is performed at the component-level first and then the system level by considering all power devices.

• 한국산학기술학회논문지
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• 제12권10호
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• pp.4561-4568
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• 2011

본 논문에서는 비엔나 정류기의 전압제어를 위한 반송파 비교 PWM 방법에 대하여 논한다. 일반적으로 산업용 및 통신용 등 여러 응용분야에서 2레벨 정류기가 주로 사용되어 왔다. 하지만 2레벨 정류기는 효율을 높이고, THD를 낮추는데 한계가 있기 때문에 3레벨 정류기에 대한 연구가 진행 되어 왔다. 3레벨 정류기의 대표적인 회로가 비엔나 정류기이다. 기존의 비엔나 정류기는 대부분 전압 명령으로부터 인가 공간전압 벡터를 선택하고, 공간전압 벡터 인가시간을 직접 계산하여, 그 시간동안 전압 명령을 인가하는 공간 전압 변조 방식이 사용된다. 하지만 이 방법은 전압 명령 생성 및 전압 벡터의 인가시간 계산이 매우 복잡하여, 구현이 어려운 단점이 있다. 이 단점을 보완하기 위해 기존의 3레벨 인버터에 사용되던 반송파 비교 PWM 방법을 비엔나 정류기에 적용할 수 있도록 수정하여, 비엔나 정류기를 위한 간단한 전압제어를 위한 반송파 비교 PWM방식을 도출하고 시뮬레이션 및 실험을 통해 검증 한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 추계학술대회 논문집
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• pp.107-108
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• 2013

본 논문에서는 3-레벨 NPC(Neutral Point Clamped) 인버터에서 사용되는 SVPWM(Space Vector Pluse Width Modulation)기법들 중 옵셋전압을 이용한 대칭 SVPWM과 효율을 높이기 위한 전압 지령 벡터를 계산한 $120^{\circ}$ DPWM(Discontinuous PWM)과 $60^{\circ}(+30^{\circ})$ DPWM을 비교 분석하였다. 각 SVPWM간의 효율 및 THD를 비교 분석 하였고 이를 통해 시뮬레이션으로 스위칭 방식에 따라 비교하여 효율 및 THD 결과를 도출하였다.