• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.347-349
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• 2005

This paper presents an efficient algorithm to estimate the maximum load level for heavily loaded power systems with the load-generation variation vector obtained by ELD (Economic Load Dispatch) and/or short term load forecasting while utilizing the elliptic pattern of the P-e curve. It is well known the power flow equation in the rectangular coordinate is fully quadratic. However, the coupling between e and f makes it difficult to take advantage of this quadratic characteristic. In this paper, a simple technique is proposed to reflect the e-f coupling effects on the estimation of maximum loadability with theoretical analysis. An efficient estimation algorithm has been developed with the use of the elliptic properties of the P-e curve. The proposed algorithm is tested on IEEE 14 bus system, New England 39 bus system and IEEE 118 bus system, which shows that the maximum load level can be efficiently estimated with remarkable improvement in accuracy.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.1
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• pp.22-30
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• 1999

This paper presents an efficient algorithm to estimate the maximum load level for heavily loaded power systems with the load-generation vector obtained by ELD (Economic Load Dispach) and/or short term load forecasting while utilizing the elliptic pattern of the P-e curve. It is well known the power flow equation in the rectangular corrdinate is jully quadratic. However, the coupling between e and f makes it difficult to take advantage of this quadratic characteristic. In this paper, the elliptic characteristics of P-e curve are illustrated and a simple technique is proposed to reflect the e-f coupling effects on the estimation of maximum loadability with theoretical analysis. An efficient estimation algorithm has been developed with the use of the elliptic properties of the P-e curve. The proposed algorithm is tested on IEEE 14 bus system, New England 39 bus system and IEEE 118 bus system, which shows that the maximum load level can be efficiently estimated with remarkable improvement in accuracy.

• Wind and Structures
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• v.5 no.6
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• pp.543-562
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• 2002

The main purpose of this study is to discuss the design wind loads for the structural frames of single-layer latticed domes with long spans. First, wind pressures are measured simultaneously at many points on dome models in a wind tunnel. Then, the dynamic response of several models is analyzed in the time domain, using the pressure data obtained from the wind tunnel experiment. The nodal displacements and the resultant member stresses are computed at each time step. The results indicate that the dome's dynamic response is generally dominated by such vibration modes that contribute to the static response significantly. Furthermore, the dynamic response is found to be almost quasi-static. Then, a series of quasi-static analyses, in which the inertia and damping terms are neglected, is made for a wide range of the dome's geometry. Based on the results, a discussion is made of the design wind load. It is found that a gust effect factor approach can be used for the load estimation. Finally, an empirical formula for the gust effect factor and a simple model of the pressure coefficient distribution are provided.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.107-117
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• 1998

In this paper, a deadbeat controller design technique is developed for the recently introduced PFC(Power Factor Correction) circuit named as a QBSRR(Quantum Boost Series Resonant Rectifier) to achieve the fast dynamic responses of the output voltage in the presense of any load variations. And, in order to monitor the load information without employing the current sensor, the load estimation method is also derived. By using the information of the load estimation method, the proposed controller gain is automatically adjusted to have the system always keep the very fast dynamic responses. To verify these superior performances, the simulation and the experiment are carried out.

• Journal of IKEEE
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• v.22 no.2
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• pp.324-329
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• 2018

As the environment of power systems changes, the demand and necessity for new electrical energy market are increasing. Especially, efforts to increase the efficiency of electric energy use by using demand response programs are being studied constantly in advanced countries and it is operated as a real market. This paper presents a study on the baseline load estimation required in the new power market, such as demand response, P2P electricity trading etc. The proposed method estimates the baeline load through analysis of the load pattern and verifies the effectiveness of the proposed method using actual data.

• Journal of the Korean Geotechnical Society
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• v.25 no.8
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• pp.57-64
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• 2009

In this study, a method using equivalent transformation for estimation of the axial load capacity of tapered piles is proposed. While preexistent methods for estimating the axial load capacity of tapered piles have been based on the effect of soil state and taper angle, a new design method is proposed considering cone resistance $q_c$ and equivalent transformation in sand. Through tapered pile simplified by using equivalent transformation, a new method fur quick and easy estimation of the axial load capacity of tapered pile is proposed for practical use. In order to verify the proposed method, calibration chamber test and field test were conducted. In calibration chamber test, comparison of estimated axial load capacity with measured one showed that the standard deviation and COV (Coefficient Of Variation) of estimated $Q_t$ is $0.05{\sim}0.121$, $0.04{\sim}0.05$ respectively. For field test, axial load capacity by proposed method shows 2.5% under-estimation in comparison with measured value. As a result, it is found that proposed method produces satisfactory predictions for tapered piles.

• Journal of Electrical Engineering and Technology
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• v.7 no.3
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• pp.304-311
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• 2012

So far, the importance for an accurate load model has been constantly raised and its necessity would be further more emphasized. Currently used load model for analysis of power system in Korea was developed 10 years ago, which is aggregated by applying the statistically estimated load compositions to load models based on individual appliances. As modern appliances have diversified and rapidly changed, the existing load model is no longer compatible with current loads in the Korean power system. Therefore, a measurement based load model is more suitable for modern power system analysis because it can accurately include the load characteristics by directly measuring target load. This paper proposes a ZIP model employing a Kalman-filter as the estimation algorithm for the model parameters. The Kamlan-filter based parameter identification offers an advantage of fast parameter determination by removing iterative calculation. To verify the proposed load model, the four-second-interval real data from the Korea Energy Management System (K-EMS) is used.

• Journal of Drive and Control
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• v.12 no.1
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• pp.15-20
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• 2015

For testing a newly designed ship's steering gear, a steering gear test bench with a steering gear to be tested and a load generation part should be prepared. The load given to the steering gear has to be pertinent to the load generated in a targeted ship. In this study, the authors suggest a process of estimating the load given to steering gears in ships. At first, a test for measuring the load in the steering gear of a real ship was conducted. Then, a process was developed to compute rudder driving torque and force by using basic equations including some empirical equations on ship's steering. The test results and the computation results on the load in the steering gear were compared, As a result, the process suggested in this study for estimating load in ship's steering gears was verified.

• Journal of Communications and Networks
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• v.17 no.4
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• pp.370-383
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• 2015

Effective link quality estimation is a vital issue for reliable routing in wireless networks. This paper studies the performance of expected transmission count (ETX) under different traffic loads. Although ETX shows good performance under light load, its performance gets significantly worse when the traffic load is high. A broadcast packet storm due to new route discoveries severely affects the link ETX values under high traffic load, which makes it difficult to find a good path. This paper presents the design and implementation of a variation of ETX called high load - ETX (HETX), which reduces the impact of route request broadcast packets to link metric values under high load. We also propose a reliable routing protocol using link quality metrics, which is called link quality distance vector (LQDV). We conducted the evaluation of the performance of three metrics - HETX, ETX and minimum hop-count. The simulation results show that HETX improves the average route throughput by up to 25% over ETX under high traffic load. Minimum hop-count has poor performance compared with both HETX and ETX at all of the different traffic loads. Under light load, HETX and ETX show the same performance.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.241-247
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• 2014

This paper propose a variable parameter estimations of five-phase squirrel-cage induction motor(IM) for speed control system. In order to high performance control of AC motor using a field oriented control(FOC) and direct torque control(DTC) algorithm, there are required precise motor parameters for slip calculation, flux observer, controller gain, rotor position, speed estimation, and so on. We are suggest a analyzed estimation results of the motor parameters that developing five-phase squirrel-cage IM have a stator of concentrated winding for experimental of variable input power frequency. There are results of stator winding test, no-load test, locked-rotor test, variable actual load test, and estimated parameters of equivalent circuits using manufactured experimental apparatus by IEEE Standard Test Procedure for Polyphase Induction Motors and Generators 112-2004.