• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1605-1606
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• 2015

전기철도차량은 매 순간마다 이동하는 대용량 단상부하로, 전력계통 측면에서 부하의 특성이나, 계통구성의 형태 및 제반현상이 일반 3상 전력계통과 상이한 특성을 지닌다. 이와 같이 3상 전력계통으로 부터 단상 교류로 변환하여 전기차를 운행하는 경우에는 3상 전원측 PCC(Point of Common Coupling)에 불평형을 일으켜, 역상전류를 발생시킨다. 현재는 이를 최소화하기 위해서 종래부터 사용 되어온 스코트 결선 변압기를 사용하고 있다. 하지만 특성상 두 개의 단상 시스템에 걸리는 부하량 및 역율이 동일하지 않을 경우 여전히 3상 전압불평형이 발생된다. 이에 대한 근본적인 대책으로는 급전시스템 재구성 또는 전력 설비 증설 및 보상장치의 적용을 들 수 있으나, 최근에는 전력전자 기술의 발달로 IGBT(Insulated Gate Bipolar Transistor) 소자를 이용한 BTB(Back To Back) 방식의 컨버터를 활용한 사례가 연구되고 있다. 본 논문에서는 전력계통과 전기철도의 연계 목적으로 3상-단상 BTB 모듈형 멀티레벨 컨버터 (Modular Multi-level Conveter, MMC)를 이용한 전기철도 급전 시스템의 기본구조를 제안하고, Mathworks사의 MATLAB Simulink tool를 이용하여 시뮬레이션을 통해 MMC시스템을 검토하고자 한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.1
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• pp.65-72
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• 2004

This paper proposes the novel boost input type resonant AC/DC converter. Since the proposed converter is single stage topology, it controls both of the input power factor and the output voltage at the same time, and resultingly obtains the high power factor of 99% with average current mode pulse width modulation. Especially, to accomplish the zero voltage switching, the resonance between the leakage inductance and external capacitor is used. For the theoretical consideration of the proposed converter, the six operation modes divided by means of current path are discussed, and the resonance characteristics in steady state are analyzed. To verify the validity of the proposed converter, a 200[W]($120[V_AC],\; 출력\; 48[V_DC],\; 4[A]$prototype converter was built and its experimental results were presented in this paper.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.305-311
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• 2017

In this paper, the LLC resonant converter battery charger, using adaptive turn ratio scheme, is proposed to achieve high efficiency and wide range output voltage. The LLC converter high frequency transformer has an adaptively changed turn ratio by the auxiliary control circuitry. As a result, the optimal converter design with a large magnetizing inductance is easily achieved to minimize the conduction and the turn-off losses while providing widely regulated voltage gain capability to properly charge the Li-ion battery. The proposed converter operational principle and the optimal design considerations are illustrated in detail. Finally, several simulation results verify the proposed LLC resonant converter's effectiveness.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.233-236
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• 2001

Parallel operation scheme to several transformers is adopted because of the load increase, economic problem, or load shedding. For the transformer's parallel operation, loads proportional to each transformer's capacity must be allotted, and circulation currents must be limited as much as without causing any problem in a real operation. But, both transformers in parallel operation can be tripped when either faults at lower voltage side of a transformer or faults in a bus occurs. Therefore, parallel operation scheme to distribution transformers in Korea is not adopted in a normal state but only when loaded or load-shedded. These are due to the insufficiency of the construction in communication network and AVR scheme. Besides that, those are because bus bar protection scheme to lower voltage side of a transformer is not applied. In spite of enormous initial investment costs, advanced countries take so much account of power system reliability and stable supply that they adopt the parallel operation scheme in a normal state. One of the problems in parallel operation is the overheat of transformers due to the excessive circulation currents. This paper presents the scheme that controls voltages between both transformers using circulation currents that occurs in parallel operation.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.2
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• pp.43-50
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• 2004

Percentage differential characteristic relaying(PDR) has been recognized as the principal basis for power transformer protection. Second harmonic restraint PDR has been widely used for magnetizing inrush in practice. Nowadays, relaying signals can contain 2nd harmonic component to a large extent even in a normal state, and 2nd harmonic ratio indicates a tendency of relative reduction because of the advancement of material. Further, as the power system voltage becomes higher and more underground cables are used, larger 2nd harmonic component in the differential current under internal fault is observed. And then, conventional 2nd harmonic restraint PDR exposes some doubt in reliability. It is, therefore, necessary to develop a new algorithm for performance improvement of conventional protective relaying. This paper proposes an advanced protective relaying algorithm by using voltage-current trend and flux-differential current slope characteristic. To evaluate the performance of the proposed algorithm, we have made comparative studies of PDR, fuzzy relaying and DWT relaying. The paper is constructed power system model including power transformer, utilizing the WatATP, and data collection is made through simulation of various internal faults and inrush. As the results of test, the new proposed algorithm was proven to be faster and more reliable.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.2
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• pp.174-182
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• 2007

Among the alternative energy sources, the solar energy is recognized as an important energy source and its application is increasing. Especially in future, the hybrid solar energy generation system with battery will be widely used as an independent distributed power generation system. In this paper, a solar power hybrid home generation system using a contactless power supply (CPS) that can transfer an electric power without any mechanical contact by using magnetic coupling instead of the power transfer by directly supplying the DC power to the home electric system is proposed. The proposed system consists of a ZVS boost converter, a half bridge LLC resonant converter and contact-less transformer.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.345-346
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• 2015

본 논문은 30kW, 95GHz 자이로트론을 구동하기 위한 50kV, 100kW 출력의 Cathode Power Supply(CPS) 설계에 대해 기술한다. 자이로트론 구동 시스템의 신뢰성과 효율성 향상을 위해 고효율 공진형 컨버터 토폴로지를 이용한 3개의 컨버터 모듈을 기반으로 출력단이 직렬로 구성된 모듈의 3상 운전을 통해 낮은 출력 전압 리플과 함께 아크 발생 시 부하 단으로 전달되는 에너지를 최소화 할 수 있도록 CPS를 설계한다. 또한 고전압 전원장치의 절연에 대한 신뢰성 확보와 전력밀도 향상을 위한 변압기 및 정류부의 효율적인 절연 설계 및 구현에 대하여 기술한다. 설계된 CPS의 실험결과를 통해 30kW, 95GHz 자이로 트론을 구동하기 위한 전원장치 설계의 타당성과 우수성을 검증한다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.2
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• pp.178-184
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• 2016

The motor power of the industry to use the electric energy is gradually increased. The electric motor generates a voltage drop in the starting current during startup. The starting current is started it is difficult to have an adverse effect on neighboring power systems with large motor starting when the voltage drop across the power grid. In addition to that the motor torque according to the load depending on the size of the rotation speed is changed to a motor start-up speed is important. However, the distance to the emergency generator transformers or motors from the motor capacity is smaller but short and difficult to maneuver the theory and practice of the operating characteristics of the starting characteristics of the motor used a lot of large industrial plants were measured and analyzed. Therefore, this study investigated the motor starting Analysis and interpretation for the relationship with the large motor starting torque and speed during motor starting.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.97-103
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• 2006

This paper designs mono block type with rotating high power radiography x-ray generator and studies 16kW X-ray generator possible to adapt hospital mobile radiography and industrial X-ray equipment and design. This equipment uses rotating anode type x-ray tube at high voltage generator to generate x-ray and adds rotor operating circuit to operate rotor of x-ray tube. The size of high voltage transformer and high voltage generator is minimized by high voltage high frequency inverter has 100kHz switching frequency. Also this paper shows result of x-ray tube voltage and tube current correspond to variable load.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.3
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• pp.207-217
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• 2010

Recently, the use of DC power increased due to the increased use of digital load. Power factor of input current decrease and input current harmonics increase, and conversion loss which is occurred in the AC / DC converter is a problem to provide the proper DC voltage to the device equipped with an internal AC / DC converter. Hybrid system supplies the AC power and DC power to AC load (motor load and the transformer load) and DC loads (computers, TV, LED fluorescent light) at the same time it supplies the renewable energy and utility energy taken power from Utility to user for improving the efficiency and renewable energy improvements in ease of use. This paper studies DC characteristics of traditional AC load for Hybrid distributions.