• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.500-504
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• 1997

Current source inverter drives of auto sequentially commutated type are very popular in high power applications, because of simple power circuit configuration with four quadrant operation. But the six-step current output create harmonic problems and the input power factor of such a drive is not always good. In this respect pulse width modulated drives using gate turn off thyristors ( GTO ) are finding application, especially in traction drives. However the switching and snubber loses of a GTO do not permit the inverter switching frequency go beyond a few hundred hertz.This will again introduce low frequency harmonic problems. Multi level inverters of the 3-level and 5-level can be considered as an alternative to overcome the low switching frequency harmonic problem of the 2-level GTO inverters. But with multi level inverters the complexity of the power circuit increases. In this paper a combination of multi level ( 2-level and 3-level ) inverters and multi phase induction motor ( 3-phase and 6-phase) configurations are presented for high power VSI drives for traction applications with reduced inverter switching frequency requirements coupled with reduced voltage rating for the power switch.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.442-446
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• 1998

With the advent of the high-speed microprocessor and DSP, the possibility of executing a control strategy in digital domain has become a reality. By the use of the DSP and microprocessor controller, many high power converters such as especially inverter and motor drive system may be enhanced resulting in the improved robustness to EMI, the ability to communicate the operating conditions and the ease of adjusting the control parameters. But, the digital controller using DSP or microprocessor is not applied in the high frequency switching power supplies, especially full bridge dc/dc converter. So, this paper presents the method and realization of designing a digital-to-phase shift PWM circuit for full digital controlled phase-shifted full bridge dc/dc converter with zero voltage switching. The operating principles, simulation and experimental results will be presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.255-257
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• 1994

The V/F slip frequency constant control methods are used for driving induction motor with load commutated current source inverter, that is. constant V/F and slip frequency driving is used to load commutate the inverter below the critical frequency, while constant voltage and variable frequency and slip frequency driving are used in above the critical region. In order to applicate the load commutated current source inverter to the general use, speed control range of induction noter is selected to two times at rated frequency. Therefore, economical application is possible because of the maximum reduction of the condenser of the inverter output port. The use of the proposed force commutated circuit improves the false operation of force commutated circuit and inverter commutation failure which are produced by the influence of the lower-order harmonics of the conventional load commutated current source inverter at starting.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.584-588
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• 2001

A conventional power supply to drive a microwave oven has ferro-resonant transformer and high voltage Capacitor(HVC). Though it is simple, transformer is bulky, heavy and has low-efficiency. To improve this defect a high frequency inverter type power supply has been investigated and developed in recent years. But, because of additional control circuit and switching device, inverter-type power supply is more expensive than conventional one. In this study, A new pulse power supply for Microwave Oven using novel HVC embedded high frequency transformer is proposed for down-sizing, cost reduction, and efficiency emprovement of Inverter type power supply. Also, equivalent circuit model is derived by impedance measurements. And the operation of proposed pulse power supply is verified by simulations and experimental results.

• 조명전기설비학회논문지
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• 제14권4호
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• pp.31-38
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• 2000

본 논문에서는 동기속도 이상의 풍속 영역에서 계풍연계된 DFTG(Doubly-Fed Induction Generaior) 시스템올 이용하여 발전기의 속도, 출력, 역률 제어에 대한 연구를 하였다. 이를 위하여 회전자 권선을 통하여 회전자 여자 주파수와 전압을 인가하였고,DBG의 전력소류와 등가회로의 정상상태 식을 해석하였다. 발전기의 속도와 고점차 일정출력제어는 회전자 여자주파수에 의해 이루어지고, 발전기의 정상적인 동작은 회전자 여자전류가 정격값올 넘어서는 안된다. 따라서 회전자 여자주파수에 의한 일정 출력운전상태에서 회전자 여자전류를 정격값이 되도록 회집자 여자전압을 제어여, 고정자 역률이 최적이 되도 DFIG를 운전하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1297-1300
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• 2008

A conventional linear accelerator system requires a flat-topped pulse with less than ${\pm}$ 0.5% ripple to meet the beam energy spread requirements and to improve pulse efficiency of RF systems. A pulse transformer is one of main determinants on the output pulse voltage shape. The pulse transformer was investigated and analyzed with the pulse response characteristics using a simplified equivalent circuit model. The damping factor ${\sigma}$ must be >0.86 to limit the overshoot to less than 0.5% during the flat-top phase. The low leakage inductance and distributed capacitance are often limiting factors to obtain a fast rise time. These parameters are largely controlled by the physical geometry and winding configuration of the transformer. A rise time can be improved by reducing the number of turns, but it produces larger pulse droop and requires a larger core size. By tradeoffs among these parameters, the high-voltage pulse transformer with a pulse width of 10 ${\mu}s$, a rise time of 0.84 ${\mu}s$, and a pulse droop of 2.9% has been designed and fabricated to drive a klystron which has an output voltage of 284 kV, 30-MW peak and 60-kW average RF output power. This paper describes design optimization of a high-voltage pulse transformer for high-power pulsed applications. The experimental results were analyzed and compared with the design. The design and optimal tuning parameter of the system was identified using the model simulation.

• 한국정보통신학회논문지
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• 제17권7호
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• pp.1660-1671
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• 2013

본 논문에서는 빛 에너지 하베스팅 자가발전 시스템을 위한 두 가지 구조의 전력관리 회로를 제안한다. 첫 번째는, 솔라셀이 부하가 동작할 수 있는 충분한 전압을 출력하는 경우, 전력관리회로를 통해 직접 솔라셀의 에너지를 부하로 공급하는 구조이다. 두 번째는 초소형 솔라셀이나 집적화된 솔라셀에서처럼 출력전압이 0.5V 이하로 매우 작아서 부하를 직접 구동할 수 없는 경우, 전압부스터를 사용하여 충분한 전압까지 승압한 후, 이를 전력관리회로를 통해 부하로 공급하는 구조이다. 이 두 가지 구조의 전력관리 회로는 $0.18{\mu}m$ CMOS 공정으로 설계 및 제작되었으며, 측정을 통해 성능을 비교 분석하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.430-433
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• 2003

IGBTS are widely used for the industrial inverters in the mid power range at low voltage (440V$\~$660V) application. Advantageous features of the device are simple gate drive and high speed switching capability. Due to these advantages the application of IGBTS is enlarging into the high power application. However, to increase the power handling capacity at lower input voltage level, the current rating in each bridge arm must be enlarged. Therefore the parallel operation of IGBT devices is essentially needed. This paper describes the feasible parallel structures of the power circuit for the mid & the high power inverters and introduces the important design condition for the parallel operation of IGBT devices. To verify feasibility of the IGBT parallel operation, the feature of several IGBT devices (EUPEC, SEMIKRON's IGBT) are investigated and the power stacks are implemented and tested with these devices. The experimental results show the good characteristics for the parallel operation of IGBTS.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.115-120
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• 2003

In a motor driving, the current rate is directly related to the rate of a switching device and in cost reduction, the parallel switching operation is the alternatives because it has the smaller current rate through current division. There are many investigations for the parallel switching operations to equaling the current division. However it remains many problems for practical usage. The reason is that the switching characteristics are mainly relied on the different saturation voltage of each device etc. and these factors are not altered by circuit designer. In order to compensate this problem, a proper resistance is experimently inserted to the switching device. But this method can not be the optimal solution. Therefore this paper proposes a new parallel operation which uses a parallel phase winding to remove the traditional effect of switching device such as saturation voltage according to the division of current. Also the reliable and stable driving is improved through experiments and the detailed principles.

• 한국항행학회논문지
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• 제17권1호
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• pp.132-141
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• 2013

본 논문에서는 공기제동의 문제점을 보완하기 위한 유지보수와 환경문제, 효율성, 경제성 등을 개선하기 위하여 정지에서 고속영역까지의 전 영역에서 전기제동을 사용하는 방법이 제시되었다. 전기적으로 완전제동을 위한 2가지 방법으로 인버터 출력전압의 증대에 의한 방법과 전동기와 인버터 사이에 직렬저항을 삽입하는 방법을 통하여 경제적이며 실제 적용이 가능한 제어방법인 직렬저항을 삽입하는 방법을 적용하기로 하였다. 직렬저항에 의한 전력손실을 감소시키기 위한 직렬저항을 단락 하는 방법을 사용하여 효율을 개선하고 전 영역에서의 제동력확보는 실험환경 내에서 우수한 인버터의 단자전압을 상승시키는 방법과 동일한 특성을 보였다.