• 전력전자학회논문지
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• 제10권4호
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• pp.323-330
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• 2005

본 논문에서는 고정자의 제 3고조파 전압 성분을 이용하여 브러시리스 직류 전동기의 회전자 위치를 간접 검출하는 방법을 제안하였다. 3고조파 성분은 회전자의 위치 정보를 가지고 있고 이 전압을 이용하여 전환 신호(Commutation signal)를 만들어 낼 수 있다. 따라서 전환 신호를 이용하여 구형파 전류 여자 브러시리스 직류 전동기를 센서리스로 운전하는 방식은 상지연 필터가 필요하지 않고 하드웨어적으로 전류의 전환 시점이 결정되므로 센서리스 드라이브용 프로세서의 부담을 줄일 수 있을 뿐만 아니라, 역기전력 파형과 상전류가 비교적 정확한 동기를 유지할 수 있으므로 넓은 속도 범위에서 안정적인 센서리스 운전이 가능한 방법이다.

• 조명전기설비학회논문지
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• 제27권3호
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• pp.65-78
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• 2013

To analyze influences under open fault conditions in switching devices, an integrated simulation and condition monitoring scheme for a permanent magnet synchronous generator (PMSG) based variable speed grid-connected wind turbine system are presented. Among various faults in power electronics components, the open fault in switching devices may arise when the switches are destructed by an accidental over current, or a fuse for short protection is blown out. Under such a faulty condition, the grid-side inverter as well as the generator-side converter does not operate normally, producing an increase of current harmonics, and a reduction in output and efficiency. As an effective way for a condition monitoring of generation system by online basis without requiring any diagnostic apparatus, the estimation schemes for generated voltage, flux linkage, and stator resistance are proposed and the validity of the proposed scheme is proved through comparative simulations.

• Journal of Power Electronics
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• 제17권3호
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• pp.695-703
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• 2017

In order to satisfy the urgent requirements for the overheating protection of induction motors, an approach that can be used to identify motor temperature has been proposed based on the rotor slots harmonic (RSH) in this paper. One method to accomplish this is to improve the calculation efficiency of the RSH by predicting the stator winding distribution harmonic order by analyzing the harmonics spectrum. Another approach is to increase the identification accuracy of the RSH by suppressing the influence of voltage flashes or current surges during temperature estimation based on model predictive control (MPC). First, an analytical expression of the stator inductance is extracted from a steady-state positive sequence motor equivalent circuit model developed from the rotor flux field orientation. Then a procedure that applies MPC for reducing the identification error of the rotor temperature caused by voltage sag or swell of the power system is given. Due to this work, the efficiency and accuracy of the RSH have been significantly improved and validated our experiments. This work can serves as a reference for the on-line temperature monitoring and overheating protection of an induction motor.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.618-620
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• 2003

Harmonics of sea surface temperature (SST) in the East Sea and their possible causes are examined by analyzing NOAA/AVHRR data, SSM/I wind speeds, NSCAT wind vectors, and NCEP heat flux data. Detailed spatial structures of amplitudes and phases of the seasonal cycles and their contributions to the total variance of SST have quantitatively. The Subpolar front serves as a boundary between regions of high annual amplitudes (${\geq}$10$^{\circ}$C) in the cold continental region and low amplitudes (${\leq}$10$^{\circ}$C) in the Tsushima Warm Current region. The low phase center of annual cycle is located over a seamount at 132.2$^{\circ}$E, 41.7$^{\circ}$N south of Vladivostok. Semi-annual amplitudes are significantly large leaching over 20% of the annual amplitudes in the Tatarskiy Strait and along the continental shelf off Russian coast in fall and spring, but its forcings are substantially annual. We have shown that fall cooling is attributed by direct and local wind forcing, while spring cooling is remotely forced by cold waters from sea ices in the Tatarskiy Strait.

• Journal of Power Electronics
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• 제18권6호
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• pp.1920-1929
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• 2018

In order to provide a source for nine phases suitable for 18-pulse ac to dc power, this paper proposes a new structure for a step-up asymmetrical delta-connected transformer for converting three-phase ac power to nine-phase ac power. The design allows for symmetry between the nine output voltages to improve the power quality of the supply current and to minimize the THD. The results show that this new structure proves the equality between the output voltages with $40^{\circ}-{\alpha}$ and $40^{\circ}+{\alpha}$ phase shifting and produces symmetrical output currents. This result in the elimination of harmonics in the network current and provides a simulated THD that is equal to 5.12 %. An experimental prototype of the step-up asymmetrical delta-autotransformer is developed in the laboratory and the obtained results give a network current with a THD that is equal to 5.35%. Furthermore, a finite element analysis with a 3D magnetic field model is made based on the dimensions of the 4kVA, 400 V laboratory prototype three-phase with three-limb delta-autotransformer with a six-stacked-core in each limb. The magnetic distribution flux, field intensity and magnetic energy are carried out under open-circuit operation or load-loss.

• 조명전기설비학회논문지
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• 제16권5호
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• pp.14-21
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• 2002

본 논문은 4상과5상 하이브리드형 스텝모터의 모델링, 특성해석 및 디텐트 토크에 대한 고조파 저감을 대상으로 연구하였다. 이를 위하여 기계적인 모델링을 도출하였으며 자계해석을 위해서 퍼미언스법을 이용하였다. 이러한 해석 결과 본 모델에 대한 디텐트 토크를 얻을 수 있었다. 또한 두 모델 구조에 대한 상차의 특성해석 비교를 통하여, 본 모델에 대한 디텐트 토크를 유도해 낼 수 있었다. 이때 5상 스텝모터는 4상 스텝모터에 비하여 디텐트 토크의 감소와 스텝응답이 개선됨을 알 수 있었다. 해석결과 퍼미언스분포의 크기는 평균토크의 발생에 영향을 미치며, 고조파성분의 크기가 토크 리플의 크기를 발생함을 알 수 있었다.

• 조명전기설비학회논문지
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• 제20권1호
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• pp.48-56
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• 2006

본 논문에서는 고정자의 3고조파 전압 성분을 이용하여 브러시리스 직류 전동기의 회전자 위치를 간접 검출하는 방법을 제안하였다. 3고조파 전압 성분은 회전자의 위치 정보를 가지고 있고 이 전압을 이용하여 정류 신호를 만들어 낼 수 있다. 따라서 정류 신호를 이용한 브러시리스 직류 전동기를 센서리스로 운전하는 방식은 역기전력 파형과 상전류가 비교적 정확한 동기를 유지할 수 있으므로 넓은 속도 범위에서 안정적인 센서리스 운전이 가능하다. 또한 정밀 속도 제어를 위해 PLL 회로를 적용함으로써 저속도에서도 높은 분해능을 얻을 수 있다. 따라서 기존에 속도 제어를 위해 필요했던 고가의 속도 센서인 레졸버와 엔코더 역할을 대체하여 전체적인 구동 회로의 가격을 낮출 수 있다.

• 조명전기설비학회논문지
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• 제16권2호
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• pp.9-17
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• 2002

본 연구에서는 250[W] MHD 램프용 전자식 안정기를 구성하고 안정기 효율 개선을 위한 설계법을 제안한다. 제안된 안정기는 PFC 및 half-bridge 공진 인버터로 구성되고 음향공명을 피하기 위해 구동주파수 25-35[kHz]에서 스펙트럼 확산법을 채택하였다. PFC 전단에 L-C 필터를 채택하여 고주파 전류가 입력 전원측으로 방출되는것을 억제하고 전해 커패시터에서 발생하는 고주파 충방전 전류를 인덕터를 사용하여 제한하였다. 공진부의 직류전압은 인버터 손실을 줄이기 위해 램프정격 전압의 침두치를 고려하여 결정하였다. 램프의 등가 저항과 공진회로의 특성곡선에서 인버터의 전달함수를 정의하고 램프의 전류를 제어하기 위한 제어기를 설계하였다. 실험으로 250[W] MHD 램프용 전자식 안정기를 제작하였고, 효율 96[%] 및 EMI 표준 EN50081-1을 만족하며 전도성 노이즈는 최대 57[dBuv]를 나타내었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.216-218
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• 2001

The transformer role is very important in power system operation and control; also its price is very expensive. Therefore many kinds of the efforts for transformer protection have been executed. So for as, current differential relay(87) has been mainly used for transformer protection. But current differential relaying method has several troubles as followings. Differential current can be occurred by transformers inrush current between winding1 and winding2 of transformer when transformer is initially energized. Also harmonic restrained element used in current differential relaying method is one of the causes of relays mal-operation because recently harmonics in power system gradually increase by power switching devices(SVC, FACTS, DSC, etc). Therefore many kinds of effort have been executed to solve the trouble of current differential relay and one of them is method using ratio of increment of flux linkages(RIFL) of the primary and secondary windings. This paper introduces a novel protective relay for power transformers using RIFL of the primary and secondary windings. Novel protective relay successfully discriminates between transformer internal faults and normal operation conditions including inrush and this paper includes real time test results using RTDS(Real Time Digital Simulator) for novel protective relay. A novel protective relay was designed using the TMS320C32 digital signal processor and consisted of DSP module. A/D converter module, DI/DO module, MMI interface module and LCD display module and developed by Xelpower co., Ltd.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 1996년도 봄 학술발표회 초록집
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• pp.22-22
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• 1996

;The Kwinana Shoreline Fumigation Experiment(KSFE) took place in Fremantle, WA, Australia between 23 January and 8 February, 1995. All measurement systems performed to expectation. The CSIRO DAR(Division of Atmospheric Research) LIDAR measured plume sections from near the Kwinana Power Station(KPS) stacks to up to about 5 km downstream. It also measured boundary layer aerosols and the structure of the boundary layer on some occasions. Both stages A and C of KPS were used as tracers at different times. Radiosonde and double theodolite sounding systems measured temperature, humidity, air pressure and wind structure at the coast(Woodman Point) and at the inland(ALCOA residue dump) site at intervals of roughly two hours. These were supplemented by mid afternoon soundings(radiosonde and single theodolite) by Department of Environmental Protection(DEP) at Swanbourne. The Flinders aircraft measured wind, turbulence and temperature structure of the atmospheric boundary layer, concentrations of $C0_2,\;0_3,\;S0_2\;and\;NO_x$ in the smoke plumes and surface radiation over both land and sea. CSIRO DCET(Division of Coal and Energy Technology) vehicle successfully interceptde many smoke plumes and using a range of tracers will be able to identify the various sources much of the time. Routine data from the DEP and Kwinana Industrial Council(KIC) air quality monitoring networks were also automatically logged. Murdoch University measured surface heat flux at Hope Valldy monitoring station and also at Wattleup monitoring station for the last five days. The heart of the LIDAR system is a Neodymium-doped Yttrium-aluminumgarnet(Nd:Y AG) laser operating at a fundamental wavelength of 1064 nm, with harmonics fo 532 nm and 355 nm. A small fraction of the laser beam is scattered back to the LIDAR, collected by a telescope and detedted by a photomultiplier tube. The intensity of the signal as a function of time is a measure of the particle concentration as a function of distance along the line of the laser shot. The results of nine days special field observations are summarized in detail.etail.