• 전기학회논문지P
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• 제66권1호
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• pp.21-26
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• 2017

Failure of high-voltage transmission line, which is responsible for large-scale power transmission, can be reason for system voltage instability. There are many methods to prevent voltage instability like adjustment of equipment, the generator voltage setting, and load shedding. Among them, the load shedding, have a problem of economic loss and cascading effect to power system. Therefore, the execution of load shedding, amount and timing is very important. Conventionally, the load shedding setting is decided by the preformed simulation. Now, it is possible to monitor the power system in real time by the appearance of PMU(Phasor Measurement Unit). By this reason, some of research is performed about decentralized load shedding. The characteristics of the load can impact to amount and timing of decentralized load shedding. Especially, it is necessary to consider the influence of the induction motor loads. This paper review recent topic about under voltage load shedding and compare with decentralized load shedding scheme with conventional load shedding scheme. And simulations show the effectiveness of proposed method in resolving the delayed voltage recovery in the Korean Power System.

• 한국조명전기설비학회지:조명전기설비
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• 제10권5호
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• pp.101-107
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• 1996

본 연구에서는 대규모 공장과 같은 수변전계통의 전압개선을 위한 전압보상설비의 특성을 해석하는 기법을 제시했다. 보상설비는 전력전자 기술을 이용한 SVC에 대해서 전기적인 과도특성 해석에 가장 정확안 S/W중 하나인 EMTP를 이용하여 TCR전류, 전압 및 점호특성 등을 분석하였다. 이러한 해석기법은 전압개선의 필요성이 높은 제철공장과 같은 대규모 공장의 수변전계통에서 외란에 대한 SVC의 전압개선 특성효과를 분석하는데 유용함을 보였다.

• Journal of Advanced Marine Engineering and Technology
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• 제23권3호
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• pp.346-351
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• 1999

This paper is a research for removing the hunting which came about during the parallel running of the alternators which four-pole six-phase have the converter with twelve diodes to rectify all the waves. Druing the parallel running the hunting came about under the period of 0.2-0.3{sec} not when it's load was the resistance but the capacity at the rpm band 1575[rpm] 1690[rpm] This hunting in our judgement was not come about from the general hunting causes which have been already known to but the special example. And so we checked that the hunting came about or not as per the changes of the rpm exciting current load current and converter and converter output voltage and the following facts were revealed. -The hunting occured during the constant voltage charging where r. p. m band is from 1575[rpm] to 1690[rpm] - The hunting did not came about during the constant power charging in which there was the large difference between the converter output voltage and the battery voltage. -The hunting did not came about in the low rpm band. We could see from the above facts that the existence of the hunting inducing point at the con-stant voltage charging band was the direct cause of the hunting. After trying every possible means to remove the hunting inducing point we could know that the modification of the synchronous generator is suitable for he purpos in view of the small engine room.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2011년도 후기공동학술대회 논문집
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• pp.73-73
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• 2011

In fact, asynchronous motors are used widely. Asynchronous motors which have large power (compared to the source supplies) is needed to start them in various methods. The theory of application reduced voltage to motor's stator or variable resistor fed rotor for the purpose of altering the motor's torque and power consumption characteristics is an idea that has existed for many years. These concepts have flourished mainly due to the need to limit torque and limited generator/power distribution capabilities. However, how can know exactly the time of switching steps with different types of motors as well as load characteristics is very difficult. This paper focuses on the design and development mathematical models of motor[1][2], load, ACB, asynchronous machine and then is implemented in SIMULINK in order to calculate this time, special on ships where power generation station is limited. The simulation results are both compared and discussed in detail so that it can apply to conclude the most suitable and applicable starting time for new system with various motors and load.

• 대한기계학회논문집
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• 제17권1호
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• pp.182-189
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• 1993

본 연구에서는 한곳에 적응효과가 중복되는 것을 피하고 해의 변화율이 상대 적으로 큰 곳에 대해 대등한 격자 적응효과를 주는 방법을 연구하였다. 전 유동장에 서 해의 변화율을 계산하여 하한값(threshold) 보다 큰 값을 갖는 cell에 대해 같은 크기의 가중함수(weight function) 값을 갖게 한다. 하한값(threshold)은 전체 cell 수에 대해 상위의 변화율을 갖는 cell의 백분율(percentage)로부터 구한다. 이 방법 은 하한값을 직접 대입해야 한다는 단점은 있으나 변황율이 상대적으로 큰 영역에 대 해 고른 격자 적응 효과를 줌으로 해서 격자 적응의 회수를 줄일 수 있으며 해의 발달 에 긍정적인 격자를 생성할 수 있다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.616-621
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• 2003

Fluid-elastic instability is believed to be a cause of the large-amplitude vibration and resulting rapid wear of heat exchanger tubes when the flow velocity exceeds a critical value. For sub-critical flow velocities, the random turbulence excitation is the main mechanism to be considered in predicting the long-term wear of steam generator tubes. Since flow-induced interactions of the tubes with tube supports in the sub-critical flow velocity can cause a localized tube wear, tube movement in the clearance between the tube and tube support as well as the normal contact force on the tubes by fluid should be maintained as low as possible. A simplified method is used for predicting fretting-wear damage of the double $90^{\circ}$U-bend tubes. The approach employed is based on the straight single-span tube analytical model proposed by Connors, the linear structural dynamic theory of Appendix N-1300 to ASME Section III and the Archard's equation for adhesive wear. Results from the presented method show a similar trend compared with the field data. This method can be utilized to predict the fretting-wear of the double $90^{\circ}$U-bend tubes in steam generators.

• 한국소음진동공학회논문집
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• 제24권5호
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• pp.363-373
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• 2014

In this study, computational multi-body dynamic analyses for the drivetrain system of a 5 MW class offshore wind turbine have been conducted using efficient equivalent modeling technique based on the design guideline of GL 2010. The present drivetrain system is originally modeled and its related system data is adopted from the NREL 5 MW wind turbine model. Efficient computational method for the drivetrain system dynamics is proposed based on an international guideline for the certification of wind turbine. Structural dynamic behaviors of drivetrain system with blade, hub, shaft, gearbox, supports, brake disk, coupling, and electric generator have been analyzed and the results for natural frequency and equivalent torsional stiffness of the drivetrain system are presented in detail. It is finally shown that the present multi-body dynamic analysis method gives good agreement with the previous results of the 5 MW class wind turbine system.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.143-151
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• 2001

During the past several years, the major interests of car manufacturers in development of automatic transmission were in durability and shift quality. However, a large number of researches for improving shift quality that are based on dynamic characteristics of shifting mechanism have been rarely adopted in the developing process because it is quite difficult to predict the shifting performance from the dynamics simulation. One of the important reasons for the difference between simulation results and experiments arises from the automatic transmission hydraulic system that consists of many valves with high order model and shows a lot different dynamics to temperature variation. In this work, hardware-in-the-loop simulation system for automatic transmission was developed f3r improving the accuracy of simulated result by combining the real-time simulation model with the real hydraulic system. The real-time simulation for automatic transmission model excluding hydraulic system is executed with TI's TMS320C31 DSP and the interfacing board which includes 12bit A/D, PWM signal generator and driver, serial driver ,etc is designed for acquiring the simulation data and signal interface with hydraulic system. We verified the proper operation and correctness of shifting result by comparing the off-line simulation result with that of HILS and experimental result which was performed on transmission dynamometer driven by electric motor.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.495-496
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• 2014

The suction method is the substructure installation using the water pressure difference generated by discharging water inside the pile by the pumping operation, after the intrusion by the self-weights of a large hollow steel pipe or a concrete structure. It is known as the low-noise and low-vibration method against the general pile driven method and eco-friendly, also. Most current design and safety assessment of the support structure and considering only the static load, however, the importance of dynamic behavior becomes magnified as the size of wind power generator increases. This study measures the natural frequency of the suction pile prototype about the penetration depth as a part of basic research and analyzed the interaction between the soil and the structure.

• 한국축산시설환경학회지
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• 제20권1호
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• pp.27-34
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• 2014

This study was conducted to survey and inspect the currently operating anaerobic digestion facilities for animal manure. Recently, the number of anaerobic digestion facility for livestock manure is on the rise thanks to growing interest in developing alternative energy. A anaerobic digestion system has been constructed in large scale farms or animal manure public resource center. Currently, most animal manure anaerobic digestion facilities in operation are producing biogas from the pig slurry which contains 97% water. Methane gas can be used to operate a engine generator which then produces electricity. Anaerobic digestate, a by-product of digestion, is mostly utilized as a liquid fertilizer after curing processing. Only in a few cases, it can be discharged after wastewater treatment process. The problem of anaerobic digestate treatment is the imbalance of C/N ratio. The content of N was too high to keep it into normal process.