• Journal of Electrical Engineering and Technology
• /
• 제12권4호
• /
• pp.1357-1368
• /
• 2017

The lack of controllability over the wind causes fluctuations in the output power of the wind generators (WGs) located at the wind farms. Distribution Static Compensator (DSTATCOM) equipped with Battery Energy Storage System (BESS) can significantly smooth these fluctuations by injecting or absorbing appropriate amount of active power, thus, controlling the power flow of WGs. But because of the component aging and thermal drift, its harmonic filter parameters vary, resulting in performance degradation. In this paper, Quantitative Feedback Theory (QFT) is used as a robust control scheme in order to deactivate the effects of filter parameters variations on the wind power generation power smoothing performance. The proposed robust control strategy of the DSTATCOM is successfully applied to a microgrid, including WGs. The simulation results obviously show that the proposed control technique can effectively smooth the fluctuations in the wind turbines' (WT) output power caused by wind speed variations; taking into account the filter parameters variations (structural parameter uncertainties).

• 한국광학회지
• /
• 제8권2호
• /
• pp.116-121
• /
• 1997

주위온도에 따른 레이저다이오드의 광출력의 변화는 정전류로 구동하는 경우와 정전압으로 구동하는 경우에 서로 다르다. 레이저다이오드를 정전류로 구동하는 경우에는 온도증가에 따라 밀도반전이 감소하므로 광출력이 감소한다. 그러나 정전압으로 구동하는 경우에는 이러한 열효과에 의한 광출력의 감소이외에 내부저항과 임계전압의 감소에 의한 주입전류의 증가효과가 있어서 열효과를 일부 상쇄하므로 광출력의 변화가 정전류로 구동할 때보다 적다. 특히 정전압으로 레이저다이오드를 구동하는 경우에 이 두가지 효과에 의한 광출력의 변화폭이 비슷하여 서로 상쇄되는 동작점 부근에서는 온도에 따른 광출력의 변화가 아주 적어져 정전류로 구동하는 때보다 훨씬 광출력이 안정함을 실험적으로 확인하였다.

• 센서학회지
• /
• 제14권5호
• /
• pp.350-356
• /
• 2005

We have developed a dual-channel type automatic measurement system to evaluate AC-DC current transfer difference of the thermal current converter(TCC) which is primary standard of AC current. The output drift effect of the TCC is minimized by measuring simultaneously the output voltages of two TCCs using voltmeter. Furthermore, the offset voltage of the voltmeter is cancelled nearly out by taking the average values of two outputs of TCCs measured with the forward-reverse directions using dual channel scanner. The uncertainties of the automatic system were 7 to $86{\mu}A/A$ for 3 mA to 10 A at 40 Hz to 20 kHz, which were evaluated by the comparisons between adjacent range of TCCs and inter-comparison with national measurement institute of Germany(PTB). The capability for ac-dc transfer difference measurement was improved by one order compared with that for the manual ac-dc measurement system.

• 전자공학회논문지D
• /
• 제34D권8호
• /
• pp.41-51
• /
• 1997

The device simulator (BANDIS) which can analyze efficiently the electrical characteristics of the semiconductor devices under the three dimensional stationary conditions on the IBM PC was developed. Poisson, electon and hole continuity equations are discretized y te galerkin method using a tetrahedron as af finite element. The frontal solver which has exquisite data structures and advanced input/output functions is dused for the matrix solver which needs the highest cost in the three dimensional device simulation. The discretization method of the continuity equations used in BANDIS are compared with that of the scharfetter-gummel method used in the commercial three-dimensional device. To verify an accuracy and the efficiency of the discretization method, the simulation results of the PN junction diode and the BJT from BANDIS are compared with those of the commercial three-dimensiional device simulator such as DAVINCI. The maximum relative error within 2% and the average number of iterations needed for the convergence is decreased by more than 20%. The total simulation time of the BJT with 25542 nodes is decreased to about 60% compared with that of DAVINCI.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
• /
• pp.139-144
• /
• 2001

The objective of this study is to investigate the behavior of 1/12 scale upper-wall lower-frame reinforced concrete structure subjected to earthquake excitations. For this purpose, Taft N21E earthquake accelerogram was simulated by using 4m$\times$4m shaking table. When the input acceleration is compared to that of output, it was found that simulation of shaking table is satisfactory. From the test results with peak ground acceleration(PGA) 0.22g, which corresponds to 0.11g in prototype by the similitude law, it can be observed that the model responded in elastic behavior and that large interstory drift occurred at the lower part of the structure.

• 한국경영과학회:학술대회논문집
• /
• 한국경영과학회/대한산업공학회 2005년도 춘계공동학술대회 발표논문
• /
• pp.723-729
• /
• 2005

Traditional statistical process control(SPC) applied to discrete part industry in the form of control charts can look for and eliminate assignable causes by process monitoring. On the other hand, engineering process control(EPC) applied to the process industry in the form of feedback control can maintain the process output on the target by continual adjustment of input variable. This study presents controlling and monitoring rules adopted variable sampling interval(VSI) to change sampling intervals in a predetermined fashion on the predicted process levels for integrated EPC and SPC systems. Twelve rules classified by EPC schemes(MMSE, constrained PI, bounded or deadband adjustment policy) and type of sampling interval combined with EWMA chart of SPC are proposed under IMA(1,1) disturbance model and zero-order (responsive) dynamic system. The properties of twelve control rules under three patterns of process change(sudden shift, drift and random shift) are evaluated and discussed through simulation and control rules for integrated VSI EPC and SPC systems are recommended.

• 로봇학회논문지
• /
• 제5권4호
• /
• pp.279-285
• /
• 2010

This paper presents the use of 3 axis accelerometer for getting the gait information including the number of gaits, stride and walking distance. Travel distance is usually calculated from the double integration of the accelerometer output with respect to time; however, the accumulated errors due to the drift are inevitable. The orientation change of the accelerometer also causes error because the gravity is added to the measured acceleration. Unless three axis orientations are completely identified, the accelerometer alone does not provide correct acceleration for estimating the travel distance. We proposed a way of minimizing the error due to the change of the orientation. Pedestrian localization is implemented with the heading angle and the travel distance. Heading angle is estimated from the rate gyro and the magnetic compass measurements. The performance of the localization is presented with experimental data.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
• /
• pp.547-552
• /
• 1989

Single mode optical fiber interferometeric sensors using phase tracking homodyne detection are typically susceptible to environmentally induced temperature fluctuations and other types of disturbances. In this paper compensator is described, which is a simple and effective phase tracking feedback electronic circuit must be output signal stabilized to achieve maximln sensitivity and linearity of Mach-Zehnder fiber-optic interferomter in the presence of differential phase drift. The phase tracking range of the piezoelectric cylinder in the reference arm is .+-.3.7.pi.rad, and the probe mass about 1 gram in the sensing ann was used for measurements of the gravity acceleration.

• 마이크로전자및패키징학회지
• /
• 제21권2호
• /
• pp.23-29
• /
• 2014

Less power consumption, lower cost, smaller size and more functionality are the increasing demands for consumer electronic devices. The three dimensional(3-D) TSV packaging technology is the potential solution to meet this requirement because it can supply short vertical interconnects and high input/output(I/O) counts. Cu(Copper) has usually been chosen to fill the TSV because of its high conductivity, low cost and good compatibility with the multilayer interconnects process. However, the CTE mismatch and Cu ion drift under thermal stress can raise reliability issues. This study discribe the thermal stress reliability trend for successful implementation of 3-D packaging.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
• /
• pp.963-966
• /
• 1998

The KOMAC(KOrea Multi-purpose Accelerator Complex) linac is composed of RFQ(Radio Frequency Quadrupole), CCDTL(Coupled Cavity Drift Tube Linac) and SC(Superconducting)-linac. The required CW output power of RF system is about 25㎿ for 20㎿ proton beam power. Therefore high power RF sources are necessary for cost saving and reliability improvement. The number of klystrons for 0.5 ㎿ at 350MHz and 1 ㎿ at 700MHz are 1 and 31, respectively. In this paper, the design parameters of the klystron system including power supply and energy recovery system are presented.