• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1647-1649
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• 1998

This paper describes the power frequency voltage and its countermeasure when a 765 kV transmission line is directly connected to a 345 kV line and operated at 345 kV voltage. The summary of this result is as follows : The western route of 765 kV transmission line doesn't need any countermeasure to reduce the power frequency voltage at the receiving end. The eastern route of 765 kV transmission needs 100 Mvar(3 phase) capacity of shunt reactor at the receiving end to reduce the power frequency voltage. The use of shunt reactors in the 765 kV transmission lines has unexpected problems, one of which is induction of high voltages on a de-energized circuit of two parallel lines. This paper examined the problem of resonance on two parallel transmission circuits in one routes.

• 조명전기설비학회논문지
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• 제29권2호
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• pp.82-90
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• 2015

This paper proposes an efficient bi-directional DC/DC converter topology using multi-phase interleaved method for power storage system. The proposed converter topology is used for a power storage system using a vanadium redox flow battery(VRFB) and is configured to enable bidirectional power flow for charging and discharging of VRFB. Proposed DC/DC converter of the 4 leg method is reduced to 1/4 times the rating of the reactor and the power semiconductor device so can be reduce the system size. Also, proposed topology is obtained the effect of four times the switching frequency as compared to the conventional converter in each leg with a 90 degree phase shift 4 leg method. This can suppress the reduction of the life of the secondary battery because it is possible to reduce the current ripple in accordance with the charging and discharging of VRFB and may increase the efficiency of the entire system. In this paper, it proposed bidirectional high-efficiency DC/DC converter topology Using multi-phase interleaved method and proved the validity through simulations and experiments.

• 정신신체의학
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• 제25권1호
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• pp.63-72
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• 2017

연구목적 본 연구는 주의력결핍 과잉행동장애(attention-deficit/hyperactivity disorder, ADHD) 환자들을 대상으로 다양한 실행기능과 정량화 뇌파간의 상관성을 알아보고자 하였다. 방법 31명의 소아청소년 ADHD 환자를 대상으로 정량화 뇌파를 측정하였다. 종합주의력검사(Comprehensive Attention Test, CAT), 스트룹 색-단어 추론 검사(Color-Word Inference Test, CWIT), 선추적 검사(Trail Making Test, TMT), 카드분류검사(Card Sorting Test, CST)가 시행되었고 한국어판 주의력결핍 과잉행동장애 평정척도(Korean version of the ADHD Rating Scale, K-ARS)가 측정되었다. 결과 CAT 검사 점수와 알파, 베타 파워가 양적 상관이 있는 반면, 델타 파워와는 부적 상관이 있었다. CWIT 검사에서는 감소된 델타 파워와 증가된 베타 파워가 높은 수행수준과 관련 있었다. 높은 TMT 검사 점수는 증가된 알파 대역 파워와 관련이 있었으며, CST 검사에서 델타 파워는 높은 수행수준과 부적 상관이 있는 반면 알파, 하이 감마파의 파워와는 양적 상관을 보였다. K-ARS 점수는 알파 파워와 부적 상관을 보였다. 결론 정량화 뇌파는 ADHD 환자들의 실행기능과 상관성을 보이며 신경생리학적 지표로서의 유용성이 시사된다.

• 조명전기설비학회논문지
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• 제13권3호
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• pp.124-128
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• 1999

본 연구는 고주파 직렬공진 인버어터를 이용한 20[kHz],10[kHz]급 고효율 유도가열장치에 관한 것이다. 치가열체인 부하변동에 대해서는 인버어터의 직류 입력 전압을 가변시키고 인버어터 스윗칭을 공진 주파수를 추종해 동작시킴으로써 무료전력을 최소화 할 수 있는 회로 구성을 제시하였다. 그리고 시뮬레이션과 실험을 통해 유도가열장치의 인버어터 역률이 약0.96으로 양호함을 알 수 있었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.59-60
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• 2014

In this paper, development of laser diode driver with 2.5kW rating is presented. The driver is configured with interleaved PFC converter, high frequency full bridge DC-DC converter, two laser diode drivers and ${\mu}$-processor based controller. The system has two laser diode drivers for providing high current and low current. High current driver delivers normal output power of diode; low current driver is for providing critical current of diode for long lifetime. Computer simulation and experiment was performed for verification, as the results, developed driver performs well.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.43-45
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• 1998

ADD has developed a special BLDCM(brushless d.c. motor) that has small size and high power density. The model of BLDCM is like that of advanced nation. Design, production and test carried out with ADD and HICO. Now the performance of BLDCM is achieved 65% of design data. Also we are concerned with adhesion of magnet in rotor for high speed.

• 전력전자학회논문지
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• 제25권5호
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• pp.404-411
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• 2020

Inductive power transfer (IPT) systems for electric vehicles generally require zero phase angle (ZPA) frequency tracking control to achieve high efficiency. Current sensors are used for ZPA frequency tracking control. However, the use of current sensors causes several problems, such as switching noise, degrading control performance, and control complexity. To solve these problems, this study proposes ZPA frequency tracking control without current sensors. Such control enables ZPA frequency tracking without real-time control and achieves stable zero voltage switching operation closed to ZPA frequency within all coupling coefficient and load ranges. The validity of the proposed control algorithm is verified on LCCL-S topology with a 3.3 kW rating IPT experimental test bed. Simulation verification is also performed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.359-360
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• 2015

10kV IGCT has been recently developed and has the potential to push wind turbine systems to higher power and voltage rating. Converters employing IGCTs need snubber and OVP circuit to limit the rate of rise of current and peak over voltage across IGCT during turn on and off state respectively. The conventional RCD snubber which is used in such power converter dissipates a significant amount of power. In order to reduce the amount of energy lost by conventional RCD snubber, this paper proposes an isolated inductor snubber circuit that not only meets all of the IGCTs characteristics during on and off-state but also significantly saves the power loss. Loss analysis of conventional di/dt snubber and OVP circuit is performed for the 3-level NPC type back-to-back VSC supplied from grid voltage of 6.9kV. In comparison with the conventional snubber, isolated inductor snubber has a fewer number of components and improved efficiency leading to a reliable and efficient wind turbine systems.

• 한국기계가공학회지
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• 제13권5호
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• pp.21-27
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• 2014

Currently, wind power has become a major research field in the area of sustainable development. As one important component of a wind turbine transmission system, most instances of downtime due to a gearbox failure are caused by bearing failures. Gearboxes for wind turbines must have the highest levels of reliability over a period of approximately 20 years, withstanding high dynamic loads. At the same time, a lightweight design and cost minimization efforts are required. These demands can only be met with a well-thought-out design, high-quality materials, a high production quality and proper maintenance. In order to design a reliable and lightweight gearbox, it is necessary to analyze methods pertaining to the bearing rating lifetimes of the standard and of different companies, also including calculation methods for modification factors. This can determine the influence of the bearing lifetime.

• Journal of Power Electronics
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• 제14권1호
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• pp.30-39
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• 2014

This paper studies a new three-level pulse-width modulation (PWM) resonant converter for high input voltage and high load current applications. In order to use high frequency power MOSFETs for high input voltage applications, a three-level DC converter with two clamped diodes and a flying capacitor is adopted in the proposed circuit. For high load current applications, the secondary sides of the proposed converter are connected in parallel to reduce the size of the magnetic core and copper windings and to decrease the current rating of the rectifier diodes. In order to share the load current and reduce the switch counts, three resonant converters with the same active switches are adopted in the proposed circuit. Two transformers with a series connection in the primary side and a parallel connection in the secondary side are adopted in each converter to balance the secondary side currents. To overcome the drawback of a wide range of switching frequencies in conventional series resonant converters, the duty cycle control is adopted in the proposed circuit to achieve zero current switching (ZCS) turn-off for the rectifier diodes and zero voltage switching (ZVS) turn-on for the active switches. Finally, experimental results are provided to verify the effectiveness of the proposed converter.