• ETRI Journal
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• 제42권5호
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• pp.790-798
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• 2020

Herein, a low-ripple coarse-fine digital low-dropout regulator (D-LDO) without ringing in the transient state is proposed. Conventional D-LDO suffers from a ringing problem when settling the output voltage at a large load transition, which increases the settling time. The proposed D-LDO removes the ringing and reduces the settling time using an auxiliary power stage which adjusts its output current to a load current in the transient state. It also achieves a low output ripple voltage using a comparator with a complete comparison signal. The proposed D-LDO was fabricated using a 65-nm CMOS process with an area of 0.0056 μ㎡. The undershoot and overshoot were 47 mV and 23 mV, respectively, when the load current was changed from 10 mA to 100 mA within an edge time of 20 ns. The settling time decreased from 2.1 ㎲ to 130 ns and the ripple voltage was 3 mV with a quiescent current of 75 ㎂.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.282-283
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• 2006

A frequency relaying algorithm which is used system separation and load shedding to improve transient stability is proposed. The algorithm can trip the generator and shed load in the abnormal frequency condition. The computer simulations of load flow analysis is used to determine the amount of load to be shed in an under frequency condition. Furthermore dynamic brake energization in the simulation is performed for the control of overfrequency.

• Computers and Concrete
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• 제25권6호
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• pp.575-585
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• 2020

Based on a refined shear deformation finite strip, transient vibrations of graphene oxide powder (GOP) reinforced plates due to external pulse loads have been investigated. The plate has uniformly and linearly distributed GOPs inside material structure. Applied pulse loads have been selected as sinusoidal, linear and blast types. Such pulse loads result in transient vibrations of the GOP-reinforced plates which are not explored before. Finite strip method (FSM) has been performed for solving the equations of motion and then inverse Laplace transform technique has been employed to derive transient responses due to pulse loading. It is reported in this study that the transient responses of GOP-reinforced plates are dependent on GOP dispersions, GOP volume fraction, type of pulse loading, loading time and load locations.

• 전기학회논문지
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• 제64권7호
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• pp.971-977
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• 2015

The electric propulsion system requires more reliability and safety than the conventional propulsion system because any sudden changes of electric system would bring tremendous effects on the ship's safety and propulsion. So it is very important to consider the potential transient effects. This paper discusses one of the worst electric accident. That is, one or two of generators are out of service in normal seagoing condition. And the appropriate measures are simulated in order to prevent the frequency decline that can bring the other generator's tripping. In addition, the relation between the transient effects and the major factors(inertia of generator/motors, governor's drooping characteristic and response speed) are also identified using the ETAP software.

• 소음진동
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• 제5권2호
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• pp.247-256
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• 1995

In this paper, double exposure holographic interferometry using ruby pulse laser is formed in order to investigate the propagation of transient waves. The vibration characteristics according to the change of impact load direction, i.e., impacted in the shear direction and in the normal direction are analyzed. It was observed that the macroscopic trends of transient wave generation and propagation in the assembly of precipitator plates were almost similar regardless of the change of impact load direction. But the propagation and mixing of transient wave was advanced relatively slowly when impacted in the normal direction.

• 전산구조공학
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• 제10권3호
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• pp.145-155
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• 1997

본 연구에서는 ANSYS와 ABAQUS 상용 유한요소 코드를 이용하여 궤도차량의 정적.동적 해석을 충격하중과 주행하중에 대해서 수행하였다. 궤도차량이 충격하중을 받을 때 최대 동적 Von Mises응력은 상판의 빔보강재와 레이스링사이에서 발생하였으며 응력수준은 390-450MPa이다. 정하중에 대한 동하중수 1.6을 고려했을 경우 동적 해석과 동적하중계수가 포함된 정하중 해석은 유사한 결과를 보이고 있다. 과도응력은 주로 레이싱링 주위에서 발생하고 있다. 주행하중의 경우 최대응력은 로드휠 유기압 현가장치 #1번에서 450MPa정도이며, 정적해석과 비선형 해석의 결과가 유사하다.

• 전기학회논문지P
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• 제57권2호
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• pp.96-101
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• 2008

The field of load modeling has attracted the attention since it plays an important role for improving the accuracy of stability analysis and power flow estimation. Also, load modeling is an essential factor in the simulation and evaluation of power system performance. However, conventional load modeling techniques have some limitations with respect to accuracy for nonlinear and composite loads. Thus, precision load modeling technique and reasonable application method is needed for more accurate power system analysis. In this paper, we develop an intelligent load modeling method based. on neural network and application techniques for power system. The proposed method makes it possible to effectively estimate the load model for nonlinear models as well as linear models. Reasonable application method is also proposed for stability analysis. To demonstrate the validity of the proposed method, various experiments are performed and their results are presented.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1392-1397
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• 2003

This paper deals with a control technique of eliminating the transient vibration of a twin-drive geared mechanical system. This technique is based on a model-based control in order to establish the damping effect at the driven machine part. The control model is composed of reduced-order electrical and mechanical parts. This control model estimates a load speed converted to the motor shaft. The difference between the estimated load speed and the motor speed is calculated dynamically and it is added to the velocity command to suppress the transient vibration generated at the load. This control technique is applied to a twin-drive geared system with backlash. In the previous work, the performance of this control method is examined by simulations. In this paper, the effectiveness of this control technique is verified by experiments. The settling time of the residual vibration generated at the loading inertia can be shortened down to about 1/2 of the uncompensated vibration level.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.245-247
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• 2001

This paper presents a series of simulation results of transient stability on SCOPF operated power system whose transmission capabilities are limited by voltage stability. Three steps of voltage security guidelines, 5[%], 7[%], 10[%] are introduced to increase power transfer from generation centers to load center and observed the effects of voltage guidelines to transient stability for three kinds of load level(peak, medium, off-peak). As a result, dynamic characteristics weren't affected by the voltage security limits in model system, but became worse for the off-peak level than peak case, and sustain oscillations are observed for the all load level. This gives us some intitutions for the development and applications of security limits to use SCOPF program in open electric market.

• 전기학회논문지
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• 제58권1호
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• pp.93-99
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• 2009

In this paper, transient voltage response of Polmer Electrolyte Membrane Fuel Cell (PEMFC) stack is analyzed and voltage dynamic characteristic is modeled for optimal design of power conditioning system (PCS). According that the load is changed, the corresponding operating voltage of fuel cell stack is also varied with a certain deep and rising time due to the chemical and mechanical responses. This transient behavior can affect on the operation with respect of PI gain in controller, duty ratio, capacitor of capacitor and so on. So in this paper the detailed theoretical analysis of transient voltage dynamics is explained and the methodology of dynamic modeling is introduced. In addition, the validity and feasibility of the proposed dynamic model is verified by experimental results under various load conditions.