• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.26 no.7
• /
• pp.865-874
• /
• 2016

This research is concerned with the experimental investigation on the vibrations of a flexible two-link system for verifying the theoretical result from simplified equations of motion for the system along with the kinematical synthesis are proposed to simulate the elastic vibrations of a previous study. The structure consists of flexible two-links; The link 2 is attached to the end of the link 1. The link 1 is made of composite fiber reinforced polymer and the link 2 is an aluminum beam. In order to verify the theoretical result, a flexible two-link system operated by the AC and RC servo motors was constructed. Experimental results show that the dynamic modeling approach and the kinematical synthesis proposed in this paper are effective.

• Proceedings of the KIPE Conference
• /
• 2006.06a
• /
• pp.285-287
• /
• 2006

플라이휠 에너지 저장장치는 회전하는 물체에 에너지를 저장하고 이 에너지를 필요 시 기계적인 에너지를 변환하여 전기적 축전지이다. 플라이휠은 무정전전원장치의 직류측의 단자에서 전원을 받아 충전되며, 무정전전원장치의 입력 AC전압이 차단되어 UPS DC bus전압이 설정 값 이하로 떨어지면 저장 되어 있는 에너지를 전력변환 모듈에 의해 DC로 변환하여 UPS에 공급한다. 또한 전압 Sag, 전압의 불평형, 순간정전 및 고조파에 의한 정전에 대비하여 축전지와 플라이휠 에너지 저장장치를 조합하여 운용할 경우 축전지와 UPS의 DC BUS가 전기적으로 절연이 되어 개별 축전지 구성과 동일한 동작이 되도록 구성으로 축전지의 방전 횟수를 감소함으로써 축전지의 수명도 연장 할 수 있습니다.

• Journal of Electrical Engineering and Technology
• /
• v.5 no.3
• /
• pp.435-442
• /
• 2010

This paper proposes an 18-step back-to-back (BTB) voltage source converter using four sets of 3-Level converter modules with auxiliary circuits to increase the number of steps. The proposed BTB voltage source converter has the independent control capability of active power and reactive power at the interconnected ac system. The operational feasibility of the proposed BTB converter was verified through many simulations with PSCAD/EMTDC software. The feasibility of hardware implementation was verified through experimental results with a scaled hardware prototype. The proposed BTB converter could be widely applied for interconnecting the renewable energy source to the power grid.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.5B no.4
• /
• pp.337-342
• /
• 2005

Direct torque control (DTC) was originally developed for induction machine drives, and, more recently has been applied to permanent magnet brushless AC (BLAC) drives. In this paper, the performance of DTC controlled brushless DC (BLDC) drives is compared with that of PWM current controlled BLDC drives, both with and without current shaping. Both simulation and experimental results are presented, as well as the analysis of the resulting torque waveforms. It is shown that, in addition to exhibiting a fast torque response, a DTC controlled BLDC drive has a significantly lower low-frequency torque ripple than the PWM current controlled BLDC drive without current shaping, and that it is easier to implement than PWM current control with current shaping.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.49 no.6
• /
• pp.272-279
• /
• 2000

This paper describes a controller design and dynamic performance analysis of UPFC based on 3-level inverters. Major attention is focused on the controller design for both shunt and series inverters, including regulator design for the dc link voltage sharing across the dc capacitors. An energy-based approach was investigated for effectively designing the controller. A detailed UPFC model has been developed with EMTP using 24-pulse 3-level inverters to verify this approach. Simulation results about dynamic performance of UPFC confirm effects for increasing transmission capacity and damping low-frequency oscillation. The developed simulation model would be very effective to analyze the dynamic performance of UPFC.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.2B no.3
• /
• pp.109-114
• /
• 2002

This paper analysis the transient performance of the modified excitation system using 4-quadrant chopper for a synchronous machine connected to HVDC system. Conventionally, capacitors are used to supply reactive power requirement at a strong converter bus. And the installation of a synchronous machine is essential in an isolated weak network to re-start after a shutdown of HVDC and to increase the system strength. However, a conventional static excitation system has some problems which are harmonic instability and the system stress due to overvoltage. To reduce these problems, the new excitation system, which has 4-quadrant chopper, is proposed. As the proposed system provides the capability to allow reverse current and isolate between AC network and excitation power, problems of overvoltage and harmonic instability can be solved. The investigation is performed and confirmed by the time domain digital simulation using PSCAD/EMTDC program.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.5B no.4
• /
• pp.358-365
• /
• 2005

In induction machine drive without a speed sensor, the estimation of the motor flux and speed often becomes deteriorated at low speeds with low back EMF. Our analysis shows that, in addition to the state resistance variation, the estimated value of field orientation angle is often corrupted by accumulative errors from the integration of voltage variables at motor terminals that have low signal/noise ratio at low frequencies. A repetitive loop path of integration in the feedback can amplify this type of error, thus speeding up the degradation process. The control system runs into information starvation due to the loss of correct field orientation. The machine's spiral vectors are controlled only in a reduced dimension in this situation. A novel control scheme is developed to improve the control performance of motor's current, torque and speed at low frequencies. The scheme gains a full-dimensional vector control and is less sensitive to the combined effect of the error sources at the low frequencies. Experimental tests demonstrate promising performances are achievable even below 0.5 Hz.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.926-928
• /
• 1999

Treeing inhibitors of barbituric acid derivatives effects on the electrical properties of crosslinked low density polyethylene under radiation environments were investigated. The electrical parameters for tree inception voltage, AC breakdown strength, volume resistivity, capacitance and dissipation factor at 1MHz and thermoluminescence, gel content measurements were discussed as a function of irradiated dosages. From the results, barbituric acid among the treeing inhibitors was shown the best treeing and radiation resistance.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.50.1-50.1
• /
• 2011

전력수요가 적을 때 잉여전력을 저장하고 전력수요가 많은 시간대나 전기료가 비싼 시간대에 저장된 전력을 사용함으로서 전력의 활용 효율을 높이고, 전력공급 시스템을 안정화하기 위해 에너지저장시스템의 연구가 최근에 활발히 진행되고 있다. 또한 공장, 산업용빌딩이나 병원 등 고르고 안정적인 전력의 수요는 늘어나고 있으며, 화석 연료 고갈 문제로 인한 신재생에너지 발전의 중요성도 대두되고 있다. 본 논문에서는 무정전 전원장치, 태양광발전시스템, 에너지 저장 시스템을 모두 통합하였다. 제안한 시스템은 3상 인버터, 부스트 컨버터, 양방향 컨버터, 사이리스터 스위치로 구성된다. 인버터는 계통과 연계되거나 UPS 동작 시 AC 전력을 만든다. 부스트 컨버터는 태양광 패널과 연결되어 MPPT 제어를 수행한다. 양방향 컨버터는 잉여전력을 배터리에 저장을 하고, 전력이 부족할 시에는 배터리의 전력을 방전한다. 사이리스터 스위치는 정전 시 계통과 부하를 끊어주는 역할을 한다. 본 논문에서는 15kW급 시스템으로 구현하여 검증하였다.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.36 no.1
• /
• pp.3-8
• /
• 1987

The conventional autosequentially commutated current-fed inverter (ASCI) is widely employed with the induction motor drives for speed control. Howener, this inverter has a limit of high power and high frequency indution motor drives. One of the limitations is to be found in the commutation capacitors in the main circuit of this inverter. A new current-fed gate turn-off thyristor (GTO) inverter is developed. This inverter is composed of the main GTO bridge configuration and the improved energy rebound circuit (ERC)without the commutation capacitor. This inverter works stable at high frequency from light load to heavy one. The improved ERC is used not only to rebound the load reactive power to the dc link, but also to return the power in the load to the ac source. The new GTO inverter circuit and the characteristics of the inverter induction motor drives are explained and analyzed.