• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.7
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• pp.1161-1168
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• 2016

Battery energy storage system(BESS) attract the attention of the power system operators with its fast response to a disturbance in spite of its limited energy capacity. This paper proposes the operating method of BESS for following the Automatic Generation Control(AGC) frequency control which is centrally distributed by a system operator. As BESS needs to just meet the control requirement from the system operator, it should be able to properly manage the state of charge(SOC) of BESS to be available to control signal. For doing these, the proposed method distributes the control requirement to available batteries in proportion to its SOC. In addition, unavailable batteries are controlled to recover the SOC to an appropriate range, and the recovering power is supplied by available batteries meeting the control requirement. Moreover, the proposed method manages the efficiency of power conversion system (PCS) by limiting the number of PCS to be assigned for the low control requirement. Finally, the case studies are carried out to verify the effectiveness of proposed strategy.

• ETRI Journal
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• v.33 no.4
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• pp.611-620
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• 2011

Since card-type one-time password (OTP) generators became available, power and area consumption has been one of the main issues of hardware OTPs. Because relatively smaller batteries and smaller chip areas are available for this type of OTP compared to existing token-type OTPs, it is necessary to implement power-efficient and compact dedicated OTP hardware modules. In this paper, we design and implement a low-power small-area hardware OTP generator based on the Advanced Encryption Standard (AES). First, we implement a prototype AES hardware module using a 350 nm process to verify the effectiveness of our optimization techniques for the SubBytes transform and data storage. Next, we apply the optimized AES to a real-world OTP hardware module which is implemented using a 180 nm process. Our experimental results show the power consumption of our OTP module using the new AES implementation is only 49.4% and 15.0% of those of an HOTP and software-based OTP, respectively.

• Journal of Communications and Networks
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• v.13 no.5
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• pp.456-462
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• 2011

This paper investigates the outage behavior of peak interference power limited cognitive radio (CR) networks with multiple transmit antennas. In CR-multi-input single-output (MISO) channel, the total transmit power is distributed over the transmitantennas. First, we use the orthogonal space-time codes (STC) to achieve the transmit diversity at CR-receiver (rx) and investigate the effect of the power distribution on the interference power received at the primary-receiver (P-rx). Then, we investigate the transmit antenna selection (TAS) scheme in which the CR system selects the best transmit antenna and allocates all the power to the selected best antenna. Two transmit antenna selection strategies are proposed depending on if feedback channel is available or not. We derive the closed form expressions of outage probability and outage capacity of all schemes with arbitrary number of transmit-antennas. We show that the proposed schemes significantly improve the outage capacity over the single antenna systems in Rayleigh fading environment. We also show that TAS based scheme outperforms the STC based scheme when peak interference power constraint is imposed on the P-rx only if a feedback channel from CR-rx to CR-transmitter is available.

• 전기의세계
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• v.27 no.1
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• pp.49-55
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• 1978

This paper describes a computer method for power system planning. Power system planning was usually studied through individual programs. Because of the laborious work involved in data preparation, the increase of task for power system planning and the time required for the detailed analysis of results, the available time for assessment and decision making has been sacrificed. In order to improve the above situation, the use of data base techniques an the simplified evaluation of the presented programs were newly developed. This program has been used successfully for the routine of power system planning in Korea Electric Company. In addition, this paper describes some results of analysis and evaluation of power system planning in KECO.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.129-132
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• 2000

In this paper, a 1.8㎓ low noise amplifier was designed and simulated using 0.2$\mu\textrm{m}$ Si CMOS process. Noise characteristics and s parameters were extracted for the 300$\mu\textrm{m}$ gate width and 0.25$\mu\textrm{m}$ gate length NMOS transistors. For high available power gain, each stage was designed cascode type. It revealed available power gain of 23.5dB, noise figure of 2.0dB, power consumption of 15㎽ at 2.5V. It was shown that designed low noise amplifier had good RF performance. Designed Si CMOS LNA is expected to be used for RF front-end in transceiver.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.345-347
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• 2008

Available transfer capability(ATC) is an important indicator of the usable amount of transmission capacity accessible by several parties for commercial trading in power transaction activities. This paper deals with an application of optimization technique for available transfer capability(ATC) calculation and analyzes the results of ATC by using several variables of optimal power flow. The method proposed is applied to the modified IEEE 14 buses model system.

• Structural Engineering and Mechanics
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• v.64 no.1
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• pp.93-107
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• 2017

The article presents the vibration and acoustic responses of un-baffled doubly curved laminated composite panel structure under the excitation of a harmonic point load. The structural responses are obtained using a simulation model via ANSYS including the effect various geometries (cylindrical, elliptical, spherical and hyperboloid). Initially, the model has been established by solving adequate number of available examples to show the convergence and comparison behaviour of the natural frequencies. Further, the acoustic responses are obtained using an indirect boundary element approach for the coupled fluid-structure analysis in LMS Virtual.lab by importing the natural frequency values. Subsequently, the values for the sound power level are computed using the present numerical model and compared with that of the available published results and in-house experimentally obtained data. Further, the acoustic responses (mean-square velocity, radiation efficiency and sound power level) of the doubly curved layered structures are evaluated using the current simulation model via several numerical experimentations for different structural parameters and corresponding discussions are provided in detail.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.74-79
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• 2006

General formula are presented for the maximum power available from the tidal head in a closed basin and from the tidal currents in a channel connecting two large bodies of water. In the latter case, the available energy cannot be estimated from the kinetic energy flux in the undisturbed state, but can be obtained from knowledge of the tidal head between the ends of the channel and the maximum volume flux in the undisturbed state. The results are supported by detailed calculations for Johnstone Strait, British Columbia, using a two-dimensional finite element model. The model also allows an extension to the case of multiple channels. More work is needed to allow for partial tidal fences which do not occupy the whole cross-section of a channel.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.8
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• pp.446-453
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• 2004

This paper focuses on the evaluation of FACTS control on available transfer capability(ATC) enhancement. Technical merit of FACTS technology on ATC boosting are analyzed. More effective control means for line flow and bus voltage are required for appling FACTS. In this paper, the power flow calculation method for deriving FACTS control parameters based on current injection model(CIM) and newton method. Integrated scheme for ATC calculation considering dynamic characteristic of power system is suggested. Study is based on the IEEE 57-bus system demonstrate the effectiveness of FACTS control on ATC enhancement.

• ETRI Journal
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• v.44 no.4
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• pp.531-542
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• 2022

With the increasing demand for unlicensed spectrum, several regulators have been opening up the 6-GHz band for unlicensed use while ensuring compliance with the technical requirement to avoid harmful interference in the existing primary services (PSs). In this paper, we present two methodologies, a channel-based method and a frequency-based method, which are applicable to a frequency coordination system that calculates the permissible transmit power in the channels or frequencies available to a secondary service (SS). In addition, we have demonstrated that the available transmit power of an SS can be maximized by adjusting the power allocation of the assigned resource units under the condition that the channel of the SS is partially overlapped with that of the PS. Based on the analysis results, it is suggested that it would be better to utilize the two methods selectively according to the operating channel conditions of the PS and the SS.