• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.360-364
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• 1995

A zero voltage switching (ZVS) three level resonant pole inverter is presented for high power GTO inverters. The concept of auxiliary resonant commutated pole(ARCP) for two level inverter is extended to the three level inverter. The proposed auxiliary commutation circuit consists of one resonant inductor and two bi-directional switches, which provides ZVS condition to the main devices without increasing device voltage or current stresses. The auxiliary device operates with zero current switching(ZCS) which enables use of the low cost thyristors. The proposed circuit can handle higher voltage and higher power(1-10MVA) comparing to the two level one. Operation and analysis of the proposed circuit are illustrated. Experimental results with 10 KW, 4 kHz prototype are presented to verify the principle of operation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.791-794
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• 2004

This paper made an induction heating inverter. The inverter is the $20\~40[kHz]$ a resonant inverter which uses a high frequency. We use this inverter and use induction heating. A phasor shift ordered a gate signal to adjust an inverter's output. We verified an output waveform according to the situation of a gate signal through the simulation. We made the inverter really and got the result.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.203-206
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• 2000

This paper presents a torque ripple reduction technique of direct torque control(DTC) for high power induction motors driven by 3-level inverters with the inverter switching frequency limited around 0.5-1kHz level. It is noted that conventional DTC algorithms to reduce torque ripple are devised for applications with relatively high switching frequency above 2-3kHz. A new DTC algorithms especially for low switching frequency inverter system illustrates relatively reduced torque ripple are devised for applications with relatively high switching frequency above 2-3kHz. Anew DTC algorithm especially for low switching frequency inverter system illustrates relatively reduced torque ripple characteristics Simulation and experimental results show the effectiveness of the proposed control algorithm

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.475-478
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• 2001

In performing the three-level SVPWM, it is nearly impossible to control the neutral-point potential exactly to the half of the dc-link voltage at all times. Therefore the inverter would produce an erroneous output voltage by this voltage unbalance. So the voltage unbalance has to be compensated in doing PWM, when the voltage unbalance occurs whether it is small or large, to make the inverter output voltage follow the reference voltage exactly the same. In this paper, a new compensating method for the neutral-point potential variation in a three-level inverter space vector PWM (SVPWM) is presented. By using the proposed method, the output voltage of the inverter can be made same as the reference voltage and thus the current and torque ripple of the inverter driven motor can be greatly improved even if the voltage unbalance is quite large. The proposed method is verified experimentally with a 3-level IGBT inverter.

• 전력전자학회논문지
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• 제27권6호
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• pp.535-540
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• 2022

DC-link capacitors are reliability-critical components in a photovoltaic (PV) inverter. Typically, the lifetime of a DC-link capacitor is evaluated by considering the voltage and hot-spot temperature of the capacitor under the specific operating condition of the PV inverter. However, the output of the PV inverter is determined by solar irradiation and ambient temperature, which vary with the seasons; accordingly, the hot-spot temperature of the capacitor also changes. Therefore, the mission profile of the PV system should be considered to effectively evaluate the reliability of the DC-link capacitor. In this study, the reliability of the DC-link capacitor of a three-level NPC inverter is comparatively analyzed with and without considering the mission profiles of the PV system, where two mission profiles recorded in Arizona and Iza are considered. The accumulated damage of the DC-link capacitor is calculated based on the lifetime model by analyzing its thermal loading. Afterward, a reliability evaluation of the DC-link capacitor is performed at the component level and then at the system level by considering all capacitors by means of Monte Carlo analysis. Results reveal the importance of performing a mission-profile-based reliability evaluation during the design of high-reliability PV inverters to achieve the target reliability performance.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권3호
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• pp.64-69
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• 2001

Energy recovery in the regenerative region is very important when SRM is used in traction drive, This is to reduce en-ergy loss during mechanical braking and/or to have a high efficiency drive during braking To control excitation voltage in motor operation and regenerative voltage in the generator operation in the SRM multi-level voltage control is effective The paper sug-gests multi-level inverter which is useful for motoring and regenerative operation in SRM

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.742-745
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• 2005

This paper describes a simple pseudo-random carrier modulation technique for the acoustic noise reduction of the three phase multi-level inverter based motor drives. The proposed method generates a new pseudo-random carrier by randomly synthesizing a carrier with fixed frequency and a carrier with opposition phase. To confirm the validity of the proposed method, a 130v three-phase multi-level inverter was Implemented and tested. The experimental results show that the output line voltage and acoustic noise harmonics spectra of an inverter have broadening effect of harmonics, as only simple synthesis of fixed frequency carries.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.448-451
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• 2000

This paper proposed a snubber circuit for flying capacitor multilevel inverter and converter. The proposed snubber circuit makes use of Undeland snubber as basic snubber as basic snubber unit and has such an advantage of Undeland snubber used in the two-level inverter. Comparing conventional RCD/RLD snubber for multilevel in verter and converter the proposed snubber keeps such a good features as fewer number of components improved efficiency of system due to low loss snubber and reduction of voltage stress of main switching devices due to low overvoltage. Furthermore the proposed concept of constructing a snubber circuit for flying capacitor 3-level inverter and converter can apply to any level of them. In this paper the proposed snubber applies to three-level flying capacitor inverter and demonstrates its feature by computer simulation and experimental result.

• 전력전자학회논문지
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• 제13권1호
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• pp.9-14
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• 2008

멀티레벨 인버터 시스템에 낮은 스위칭 주파수가 사용되면, 이들 멀티레벨 인버터 시스템은 큰 값의 저 주파수 고조파 성분을 발생한다. 일반적으로 이러한 문제를 해결하기 위해 LC필터가 인버터 시스템의 출력단에 사용되었다. 그러나 LC필터를 사용한 경우 제동저항의 사용에 의한 전압강하가 발생하고, 제동저항의 전력손실로 인해 시스템의 효율이 감소하는 문제를 야기하게 된다. 본 논문에서는 낮은 스위칭 주파수를 갖는 3상 NPC 3레벨 인버터를 위한 출력 필터 설계방법을 제안하였다. 그리고 제안된 필터 시스템의 효율을 분석하였고, 제안된 시스템의 효과는 시뮬레이션과 실험결과를 통하여 입증하였다.

• 전력전자학회논문지
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• 제14권6호
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• pp.472-480
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• 2009

본 논문은 3상 NPC형 3레벨 인버터의 과변조 SVPWM 기법과 변조비에 대한 출력전압의 고조파를 분석하였다. 3상 NPC형 3레벨 인버터는 SVPWM을 적용하여 선형영역을 0.907까지 확장하였고 과변조 영역에서는 푸리에 급수에 의한 추종전압의 보상기법을 적용하여 6 스텝영역까지 운전할 수 있도록 하였다. PWM 형태인 출력전압의 고조파 특성분석에는 PD방식의 멀티 캐리어 기법에 대하여 이중 푸리에 급수를 적용하여 해석하였다. 시뮬레이션은 PSIM을 사용하여 구현하였고 3레벨 인버터의 영역도의 각 영역에 대해서 고조파의 특성을 확인하였다. NPC형 3레벨 인버터의 고조파 분포는 선형영역에서는 캐리어 주파수의 측대 고조파가 분포되고, 과변조 영역으로 넘어가면서 기본파에 의한 고조파 성분이 점차 증가하고 캐리어 주파주의 사이드 밴드의 고조파 성분은 감소함을 확인하였다. 본 논문에서의 고조파 해석을 검증하기 위하여 동일한 조건에서 시뮬레이션과 실험을 수행하였다.