• 한국산업융합학회 논문집
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• 제20권2호
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• pp.115-124
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• 2017

This paper aims to develop an SMPS topology for handling a high range of input voltages based on a DC-DC flyback converter circuit. For this purpose, 2 capacitors of the same specifications were serially connected on the input terminal side, with a flyback converter of the same circuit configuration serially connected to each of them, so as to achieve high input voltage and an effect of dividing input voltage. The serially connected flyback converters have the transformer turn ratio of 1:1, so that each coil is used for the winding of a single transformer, which is a characteristic of doubly-fed configuration and enables the correction of input capacitor voltage imbalance. In addition, a pulse transformer was designed and fabricated in a way that can achieve the isolation and noise robustness of the PWM output signal of the PWM controller that applies gate voltage to individual flyback converter switches. PSIM simulation was carried out to verify such a structure and confirm its feasibility, and a 100W class stack was fabricated and used to verify the feasibility of the proposed high voltage SMPS topology.

• Journal of Electrical Engineering and Technology
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• 제4권2호
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• pp.211-218
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• 2009

This paper presents a voltage and frequency controller (VFC) for a 4-wire stand-alone wind energy conversion system (WECS) employing an asynchronous generator. The proposed VF con-troller consists of a three leg IGBT (Insulated Gate Bipolar Junction Transistor) based voltage source converter and a battery at its DC bus. The neutral terminal for the consumer loads is created using a T-connected transformer, which consists of only two single phase transformers. The control algorithm of the VF controller is developed for the bidirectional flow capability of the active power and reactive power control by which it controls the WECS voltage and frequency under different dynamic conditions, such as varying consumer loads and varying wind speeds. The WECS is modeled and simulated in MATLAB using Simulink and PSB toolboxes. Extensive results are presented to demonstrate the capability of the VF controller as a harmonic eliminator, a load balancer, a neutral current compensator as well as a voltage and frequency controller.

• 조명전기설비학회논문지
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• 제22권4호
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• pp.35-45
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• 2008

본 논문에서는 대용량 출력에 적합한 Three-Level 컨버터에 대하여 논하였다. 전력 변환 시스템에서 에너지의 저장, 변환, 전기적 절연 및 필터 등을 위한 자성체의 적절한 설계는 매우 중요하다. 제안된 Three-Level 컨버터는 출력단 인덕터와 변압기의 결합을 통하여 자성체의 수를 저감하였다. 본 연구에서는 Three-Level 컨버터에서 자기회로 해석을 기반으로한 릴럭턴스 모델을 제안하고자 한다. 또한, 단일 코어 변압기 결선에 의한 2차측 정류방식에 대하여 논하고자 한다. 본 연구에서는 IGBT를 사용하여 입력 540[V], 출력 48[V], 3[kW]급 시스템을 제작했으며 40[kHz]에서 실험하였다.

• 전기학회논문지
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• 제58권1호
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• pp.35-41
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• 2009

This paper proposes a stand alone type single-phase fuel cells micro-source with a voltage sag compensator for compensating the ac output voltage variations (sag or swell) of micro-source. The proposed micro-source is consist of a PEM(polymer electrolyte membrane) fuel cells simulator, a full bridge de converter, a 60Hz PWM(pulse width modulation) VSI(voltage source inverter), and a voltage sag compensator. Voltage sag compensator is similar to the configuration of hybrid series active power filter, and it is directly connected to micro-source through the injection transformer. Compensation algorithm of a voltage sag compensator adopts a single phase p-q theory. Effectiveness of the proposed the system is verified by the PSIM(power electronics simulation tool) simulation in the steady state and transient state which the proposed system is able to simultaneously compensate the harmonic current and source voltage sag or swell.

• 전기학회논문지
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• 제58권8호
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• pp.1544-1550
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• 2009

In this paper, a new single phase voltage sag/swell compensator using direct power conversion is proposed. A new compensator consists of input/output filter, series transformer and direct ac-ac converter, which is a single-phase back-to-back PWM converter without dc-link capacitors. Advantages of the proposed compensator include: simple power circuit by eliminating dc link electrolytic capacitors and thereby, improved reliability and increased life time of the entire compensator; simple PWM strategy or compensating voltage sag/swell at the same time and reduced switching losses in the ac-ac converter. Further, the proposed scheme is able to adopt simple switch commutation method without requiring complex four-step commutation method that is commonly employed in the direct power conversion. Simulation and experimental results are shown to demonstrate the advantages of the new compensator and PWM strategy. A 220V, 3kVA single-phase compensator based on the digital signal processor controller is built and tested.

• 전력전자학회논문지
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• 제3권2호
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• pp.148-155
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• 1998

역률개선을 위한 변압기 자기에너지 궤환 기법을 이용한 새로운 단일 전력단, 단일 스위치 방식의 AC/DC 컨버터를 제안한다. 제안한 컨버터의 동작원리 및 해석을 수행하였다. 제안한 컨버터는 선전류 고조파 왜곡이 작으며 고역률 및 정확한 전압 조정이 가능하다. 실험모델은 단일 역률에 가까운 역률을 보이며 IEC 555-2를 충분히 만족시킨다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.94-97
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• 1998

The conceptual design of integrated three phase superconducting fault current limiter (SFCL) is presented. And through simulation of power system where this SFCL is installed, the characteristics of this SFCL is analyzed. It is like three-phase transformer. So it has the same characteristics with inductive single phase SFCL. But it has more merits than single phase SFCL. Differently to single phase SFCL, integrated three phase SFCL induces impedance at all phase by any single phase fault to protect the power system more safely.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1671-1673
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• 2003

Faraday효과를 기본으로 하는 광CT(Optical Current Transformer)는 기존의 CT의 결점을 개선하여 경제적 효과의 증대, 신호제어 시스템의 신속성향상, Digital 계전시스템의 호환성에 크게 기여한다는 점 등 많은 면에서 장점을 가지고 있다. 본 연구에서는 광섬유센서 기술을 응용하고, Faraday 효과의 편광면 회전량을 수광부에서 김출하여 대전류 측정을 위한 광 CT의 동작특성에 대한 실험을 하고자 한다. 실험에 사용찬 광원은 633[nm] He-Ne Laser와 1310[nm] Laser Diode 두 가지로 동일한 시스템으로 구성하여 비교한다. 센싱부의 광섬유는 길이 10[m]의 633[nm] 1310[nm]용 single-mode bare fiber를 전류가 흐르는 케이블에 감아 센싱부를 구성하고, 전류변화에 따른 두 출력값을 측정, 비교하고자 한다.

• 전기학회논문지P
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• 제57권3호
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• pp.302-310
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• 2008

In order to evaluate the nominal rating of breakers in distribution system due to the increased capacity and operating conditions of power transformers in 154 kV substation, the fault currents in distribution system were calculated by the conventional method and simulations of PSCAD/EMTDC program. Consequently, under the condition of the parallel operation of transformers, the fault currents exceed the nominal current of the breakers in some areas. Without NGR at the secondary neutral of the transformer, the current of single line-to-ground fault was bigger than that of 3-phase fault. Therefore, the results clearly show that the measures to limit the fault currents in distribution system are needed when the increased capacity of power transformers is introduced into 154 kV substation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.744-746
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• 2002

In this paper the method to limit inrush currents for unloaded transformers is proposed by controlling the opening instant in order to predetermine the residual flux. For the purpose of verifying the performance of the proposed method the test circuit with a single phase transformer is established and the effect of the controlled method is studied. With the basis of the obtained results the controlled method for three phase transformers with a wye-delta winding is also proposed. The analysis studies using EMTP(Electro-Magnetic Transient Program) are carried out in order to reveal its effectiveness.