• 전기학회논문지
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• 제60권8호
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• pp.1492-1501
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• 2011

A wide-area protection intelligent technique has been used to improve a reliability in power systems and to prevent a blackout. Nowadays, voltage and current phasor estimation has been executed by GPS-based synchronized PMU, which has become an important way of wide-area blackout protection for the prevention of expending faults in power systems. As this technique has the difficulties in collecting and sharing of information, there have been used a FNET method for the wide-area intelligent protection. This technique is very useful for the prediction of the inception fault and for the prevention of fault propagation with accurate monitoring frequency and frequency deviation. It consists of FDRs and IMS. It is well known that FNET can detect the dynamic behavior of system and obtain the real-time frequency information. Therefore, FDRs must adopt a optimal frequency estimation method that is robust to noise and fault. In this paper, we present comparative studies for the frequency estimation method using IRDWT(improved recursive discrete wavelet transform), for the frequency estimation method using FRDWT(fast recursive discrete wavelet transform). we used the Republic of Korea 345kV power system modeling data by EMTP-RV. The user-defined arbitrary waveforms were used in order to evaluate the performance of the proposed two kinds of RDWT. Also, the frequency variation data in various range, both large range and small range, were used for simulation. The simulation results showed that the proposed frequency estimation technique using FRDWT can be the optimal frequency measurement method applied to FDRs.

• Journal of Power Electronics
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• 제18권1호
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• pp.234-250
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• 2018

This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method.

• 전력전자학회논문지
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• 제3권3호
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• pp.206-213
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• 1998

본 논문에서는 유도전동기의 속응 토크제어를 위한 파라미터 변동의 적응보상기법을 제안하였다. 제어성능을 현저히 저하시키는 원인으로 작용하는 파라미터의 변동을 보상하기 위하여 본 논문에서는 모델기준 적응제어(MRAC)방식을 적용하여 회전자 저항값 변동을 추정 보상한다. 본 적응제어방식은 실측 순시무효전력과 추정 순시무효전력의 오차관계에서 실시간으로 회전자 저항값 변동을 추정 보상하는 방식이다. 본 방식은 전동기 파라미터를 사용하지 않고 실측 순시무효전력을 기준모델로 적용하기 때문에 전동기 등 등가모델에서 구한 기존의 다른 기준모델에 비해 강인한 시스템이 된다. 추정된 회전자 저항값을 이용하여 자속관측기를 구성하고 이를 직접베터 제어방식에 적용하였으며, 시뮬레이션 및 실험을 통하여 속응 토크제어가 원활히 수행됨을 입증하였다.

• 한국통신학회논문지
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• 제32권5A호
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• pp.503-509
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• 2007

저전력 움직임추정은 휴대용 정보단말의 실시간 비디오 코딩에 필수적이다. 본 논문에서는 전역탐색 블록정합 방식을 적용한 저전력 움직임추정 알고리즘과 이를 1차원 배열의 VLSI로 구현한 하드웨어 구조를 제안한다. 전역 탐색 블럭정합 방법의 전력소비의 주원인은 많은 연산량과 탐색영역의 프레임 데이터를 호출하는 횟수가 많다는 점이다. 본 논문에서는 두 개의 인접한 참조블럭의 움직임추정 연산을 동시에 병렬로 수행하여 탐색영역의 메모리 호출횟수를 감소시켰으며, 움직임추정시 결과에 영향을 미치지 않는 불필요한 연산을 제거하였다. 제안된 움직임추정 알고리즘을 1차원 PE (processing element) 배열구조의 VLSI로 구현하여 실험한 결과, 제안된 움직임추정기는 기존의 저전력 움직임추정기에 비해 9.3%의 소비전력 감소와 2배 정도의 속도향상이 있음을 확인하였다.

• 한국멀티미디어학회논문지
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• 제24권1호
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• pp.67-74
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• 2021

As IoT(Internet Of Things) devices like a smart sensor have constrained power sources, a power strategy is critical in WSN(Wireless Sensor Networks). Therefore, it is necessary to figure out the residual power of each sensor node for managing power strategies in WSN, which, however, requires additional data transmission, leading to more power consumption. In this paper, a residual power estimation method was proposed, which uses ignorantly small amount of power consumption in the resource-constrained wireless networks including WSN. A residual power prediction is possible with the least data transmission by using Machine Learning method with some training data in this proposal. The performance of the proposed scheme was evaluated by machine learning method, simulation, and analysis.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2012년 추계학술대회
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• pp.461-471
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• 2012

Most useful statistical techniques in six sigma DMAIC are hypothesis testing and interval estimation. So this paper reviews and derives sample size formula by considering significance level, power of detectability and effect difference. The quality practioners can effectively interpret the practical and statistical significance with the rational sample sizing.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1721-1726
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• 2004

Heat rate is a representative index to estimate the performance of turbine cycle in nuclear power plant. Accuracy of heat rate calculation is dependent on the accuracy of measurement for plant status variables. Uncertainty of heat rate can be modeled using uncertainty propagation model. We developed practical estimation model of heat rate uncertainty using the propagation and regression model. The uncertainty model is used in the performance analysis system developed for the operating nuclear power plant.

• Journal of Communications and Networks
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• 제16권3호
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• pp.301-304
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• 2014

This paper proposes accurate interference probability and bit error rate formulas for cognitive relay networks with underlay spectrum sharing and channel estimation error (CEE). Numerous results reveal that the CEE not only degrades the performance of secondary systems (SSs) but also increases interference power caused by SSs to primary systems (PSs), eventually unfavorable to both systems. A solution to further protect PSs from this effect through reducing the power of secondary transmitters is investigated and analyzed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.134-136
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• 1986

In this paper, a new power spectral estimation technique is presented. At first, by transforming the original data with the Karhunen-Loeve Transform(KLT), we can reduce the amount of the redundant information. Next, by modeling the transformed data by means of the autoregressive(AR) model and then applying the least-squares parameter estimation algorithm to this model, even more accurate spectrum estimates can be obtained. The KLT is the optimum transform for signal representation with respect to the mean-square error criterion. And the least-squares method is used to overcome the inherent shortcomings of popular burg algorithm.

• 한국정밀공학회지
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• 제17권2호
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• pp.114-120
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• 2000

Fossil power plant availability is significantly affected by gradual degradations of equipment as operation of the plant continues. It is quite important to determine whether or not to replace some equipment and when to replace the equipment. Performance calculation and analysis can provide the information. Robustness in the performance calculation can be increased by using verification ＆ validation of measured input data. We suggest new algorithm in which estimation relation for validated measurement can be obtained using correlation between measurements. Input estimation model is obtained using design data and acceptance measurement data of domestic 16 fossil power plant. The model consists of finding mostly correlated state variable in plant state and mapping relation based on the model and current state of power plant.