• 전력전자학회논문지
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• 제23권3호
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• pp.168-173
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• 2018

In this paper, an auxiliary power supply (APS) for railroad cars is proposed. The APS can reduce the number of devices required to supply power through structural modification and operates at a high switching frequency by application of a SiC device. The voltage stress on the device in the proposed circuit can be reduced to less than half of the input voltage of the system; thus, a device with low breakdown voltage can be designed. By adapting a SiC device instead of an IGBT device, the proposed circuit can reduce switching and conduction losses and operate at a high switching frequency, thereby reducing output voltage and inductor current ripples in the proposed circuit. The theoretical analysis results of the proposed APS are verified with a 40 kW computer-based simulation and a 2 kW experiment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.336-338
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• 2002

We improved quench properties of a superconducting fault current limiter (SFCL) based on YBCO thin films by their serial and parallel combinations. The SFCL consisted of 6 switching elements fabricated of 4 inch-diameter YBCO thin films. Simple serial connection resulted in imbalanced power dissipation between switching elements even at the quench current difference of 0.6A. On the other hand, $2{\times}2\;and\;3{\times}2$ stack combinations produced simultaneous quenches. The $3{\times}2$ stack combination showed better simultaneous quench behavior than the $2{\times}2$ stacks. This is suggested to be because the currents between switching elements in parallel connection of the $3{\times}2$ stacks were more effectively redistributed than the $2{\times}2$ stacks.

• 전력전자학회논문지
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• 제9권2호
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• pp.178-186
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• 2004

본 연구에서는 3상 RCD(Random Pulse Centered Displacement) PWM기법에 비하여 구현이 용이하고 스위칭 주파수의 정수배 스펙트럼의 광대역화와 선형화의 효과가 우수한, 2상 RCD-PWM을 제안하였으며, 그 파워 스펙트럼을 비교하고 있다 종전의 3상 RCD-PWM과 제안된 2상 RCD-PWM을 구현하기 위하여, 16비트 고성능 마이크로 컨트롤러 SAB-Cl67이 사용되었다 SAB-C167에 의하여 각 변조 구간에서의 듀티비를 구한 후, 선형 랜덤 발생기를 이용하여 균일한 확률 분포로 각 상의 펄스의 위치를 재배치하였다. 제안된 2상 RCD-PWM에 의한 모터전압과 전류 그리고 직류링크 전류의 파워 스펙트럼 및 모터의 가청 스위칭 소음 효과를 종전의 3상 RCD-PWM과 비교 검토하였다

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.491-494
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• 2003

This paper presents a new conceptual electromagnetic induction eddy current-based stainless steel plate spiral type heater for heat exchanger or Dual Packs Heater in hot water producer, boiler steamer and super heated steamer, which is more suitable and acceptable for new generation consumer power applications. In addition, all active clamped edge resonant PWM high frequency inverter using trench gate IGBTs power module can operate under a principle oi zero voltage soft communication with PWM is developed and demonstrated for a high efficient Induction heated hot water producer and boiler in the consumer power applications. This consumer induction heater power appliance using active clamp soft switching PWM high frequency inverter is evaluated and discussed on the basis of the simulation and experimental results.

• 전력전자학회논문지
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• 제20권4호
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• pp.337-343
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• 2015

The multi-level inverters are highly efficient for high-power and medium-voltage AC driving applications, such as high-speed railway systems and renewable energy resources, because such inverters generate lower total harmonic distortion (THD) and electromagnetic interface (EMI). Lower switching stress occurs on switching devices compared with conventional two-level inverters. Depending on the multi-level inverter topology, the required components and number of switching devices are different, influencing the overall efficiency. Comparative studies of multi-level inverters based on loss analysis and output characteristic are necessary to apply multi-level inverters in high-power AC conversion systems. This paper proposes a theoretical loss analysis method based on piecewise linearization of characteristic curves of power semiconductor devices as well as loss analysis and output performance comparison of five-level neutral-point clamped, flying capacitor inverters, and high-level cascaded H-bridge multi-level inverters.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.413-414
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• 2014

This paper proposed an optimized design of a dual active bridge converter for a low-voltage charger. The dual active bridge converter among various bi-directional DC/DC converters is a high-efficiency isolated bi-directional converter. In the general design, when the battery voltage is high, the ZVS region is reduced. In contrast, when the battery voltage is low, the efficiency is low due to high conduction loss. In order to increase the ZVS region and the power conversion efficiency, depending on the battery voltage, variable switching frequency method is applied. At the same duty, the same power is obtained regardless of the battery voltage using the variable switching frequency method. The proposed method was applied to a 5kW prototype converter, and the experimental results were analyzed and verified.

• Journal of Power Electronics
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• 제18권6호
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• pp.1912-1919
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• 2018

The output capacitance of power semiconductor devices is important in determining the switching losses and in the operation of some resonant converter topologies. Thus, it is important to be able to accurately determine the output capacitance of a particular device operating at elevated power levels so that the contribution of the output capacitance discharge to switch-on losses can be determined under these conditions. Power semiconductor switch manufacturers usually measure device output capacitance using small-signal methods that may be insufficient for power switching applications. This paper shows how first principle methods are applied in a novel way to obtain more relevant large signal output capacitances of Gallium-Nitride (GaN) FETs using the drain-source voltage transient during device switch-off numerically. A non-linear capacitance for an increase in voltage is determined with good correlation. Simulations are verified using experimental results from two different devices. It is shown that the large signal output capacitance as a function of the drain-source voltage is higher than the small signal values published in the data sheets for each of the devices. It can also be seen that the loss contribution of the output capacitance discharging in the channel during switch-on correlates well with other methods proposed in the literature, which confirms that the proposed method has merit.

• 항공우주시스템공학회지
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• 제15권1호
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• pp.32-39
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• 2021

전기추진 항공기는 기존 가스터빈 엔진에 의한 환경 및 소음 문제를 해결하기 위해 최근 항공분야에서 활발히 연구가 진행되고 있다. 특히 전기 동력추진 시스템의 핵심 구성품인 추력 모터와 이를 구동하기 위한 인버터에 대한 연구가 활발히 진행되고 있다. 이에 본 논문에서는 무게와 부피에 민감한 항공기 특성에 맞는 비출력이 높은 모터를 선정하고, 전력 소자에 따른 인버터 전력 손실을 시뮬레이션 하였다. 시뮬레이션은 전력전자 분석 툴인 PSIM을 이용하여 선정된 모터와 전력 소자를 모델링하여 스위칭 주파수에 따른 인버터 전력 손실을 분석 하였다.

• 전력전자학회논문지
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• 제13권5호
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• pp.369-375
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• 2008

본 논문에서는 Z-소스 인버터를 사용하여 단상 계통 연계형 태양광 시스템을 제어하는 기법을 제시하였다. 인버터 스위칭소자의 전압 스트레스를 고려하여 광전지 출력전압에 대한 계통 연계형 Z-소스 인버터의 동작영역을 분석하였다. 스위칭 손실을 감소시키면서 shoot-through 시간을 효율적으로 제어하는 스위칭 패턴을 사용하였다. 시뮬레이션 및 32-비트 DSP를 사용한 실험을 통하여 계통연계형 Z-소스 인버터의 제어 시스템의 성능을 평가하였다.

• Journal of Power Electronics
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• 제12권1호
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• pp.128-135
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• 2012

In this paper, different switching tables proposed for the Direct Torque Controlled (DTC) of a six-phase induction machine are simulated and implemented. A six-phase induction motor has 64 space voltage vectors which result in increased complexity in the selecting of inverters switching. The unsuitable selection of a switching table leads to large harmonics especially at low speed and it also reduces drive efficiency. A six-phase induction machine has large zero sequence harmonic currents of the order $6{\kappa}{\pm}1$. These harmonic currents are varied in various techniques. Decreasing this loss is essential in a six-phase induction machine. The main purpose of this paper is to improve the ST-DTC of six-phase induction machines to reduce the voltage and current harmonics and the torque pulsation. Selecting a suitable method for minimizing these harmonics is very important.