• Journal of the Korean Solar Energy Society
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• v.27 no.2
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• pp.37-44
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• 2007

As photovoltaic(PV) power generation system becomes more common, it will be necessary to investigate islanding detection method for PV systems. Islanding of PV systems can cause a variety of problems and must be prevented. However, if the real and reactive power of the load and PV system are closely matched, islanding detection by Passive methods becomes difficult. Also, most active methods lose effectiveness when there are several PV systems feeding the same island. The active frequency drift positive feedback method(AFDPF) enables islanding detection by forcing the frequency of the voltage in the island to drift up or down. In this paper the research for the minimum value of chopping fraction gain applied digital phase-locked-loop (DPLL) to AFDPF considering output power quality and islanding prevention performance are performed by simulation and experiment according to IEEE Std 929-2000 islanding test.

• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.158-165
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• 2016

Many researches for improving detection performance in the reverberation environment have been conducted in active sonar systems. Especially the type of active pulse makes an impact on the detection performance in the reverberation environment. Thus, this paper describes the detection performance of PTFM (Pulse Trains of Frequency Modulated waveform), Costas, and Geometric Comb pulses which are known for their outstanding performance against the reverberation. Sea trial data of those pulses was analyzed and it was figured out that the range resolution of PTFM pulse was deteriorated by its sub-pulses. Costas pulse showed performance degradations of the doppler resolution by multipath signals. Geometric Comb pulse showed the best doppler resolution.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.4
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• pp.341-347
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• 2001

Harmonics and fundamental reactive current of nonlinear loads in serious unbalanced power condition, are compensated by current synchronous detection(CSD) theory which is also acceptable for single phase power system. But, the CSD theory is not suitable any more, in case of controlled independently harmonics and reactive component. Therefore, a new algorithm, the expanded current synchronous detection(ECSD) theory for a three phase active power filter based on decomposition of fundamental reactive, distorted components, is proposed in this paper. The proposed ECSD theory is experimented and tested comparison with a few power theories under asymmetrical condition in power system.

• Journal of Communications and Networks
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• v.15 no.3
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• pp.283-291
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• 2013

In this paper, we propose new multiuser detectors (MUDs) based on compressed sensing approaches for the large-scale multiple antenna systems equipped with dozens of low-power antennas. We consider the scenarios where the number of receiver antennas is smaller than the total number of users, but the number of active users is relatively small. This prior information motivates sparsity-embracing MUDs such as sparsity-embracing linear/nonlinear MUDs where the detection of active users and their symbol detection are employed. In addition, sparsity-embracing MUDs with maximum a posteriori probability criterion (MAP-MUDs) are presented. They jointly detect active users and their symbols by exploiting the probability of user activity, and it can be solved efficiently by introducing convex relaxing senses. Furthermore, it is shown that sparsity-embracing MUDs exploiting common users' activity across multiple symbols, i.e., frame-by-frame, can be considered to improve performance. Also, in multiple multiple-input and multiple-output networks with aggressive frequency reuse, we propose the interference cancellation strategy for the proposed sparsity-embracing MUDs. That first cancels out the interference induced by adjacent networks and then recovers the desired users' information by exploiting the low user activity. In simulation studies for binary phase shift keying modulation, numerical evidences establish the effectiveness of our proposed MUDs exploiting low user activity, as compared with the conventional MUD.

• Journal of IKEEE
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• v.25 no.4
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• pp.703-709
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• 2021

As drone technology advances, the risks of drones are increasing, then technology to detect drones is becoming important. In this thesis, it was verified that miniaturized and lightweighted active array antenna could be used for radar system to detect drones in reality. The transmit-receive module was designed in the form of tile-type to simplify interconnections between devices. The waveform generation module and the down conversion module were miniaturized to include in one body too. As a result of verifing the detection performance through test, it was confirmed that the detection range was over 3.7Km.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.633-638
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• 2003

In this paper, we propose a humanoid active audition system which detects the direction of sound and performs speech recognition using just three microphones. Compared with previous researches, this system which has simpler algorithm, fewer microphones and better amplifier shows better performance. In order to verify our system's performance, we install the proposed active audition system to the home service robot, called Hombot II, which has been developed at the KIST (Korea Institute of Science and Technology), thus we confirm excellent performance by experimental results

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1294-1301
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• 2005

In this paper, we investigate the problems of existing solutions for intrusion detection and propose an agent network based on stationary and mobile agents on agent system to solve them. The proposed agent network can detect intrusions, collect their information and execute active responses against intruders by introducing various stationary and mobile agents. It will show a new approach of active responses against more intelligent and distributed intrusions.

• Journal of Power Electronics
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• v.2 no.1
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• pp.1-10
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• 2002

An advanced active power filter for the compensation of instantaneous harmonic current components in nonlinear current load is presented in this paper. A novel signal processing technique using an adaptive neural network algorithm is applied for the detection of harmonic components generated by three-phase nonlinear current loads and this method can efficiently determine the instantaneous harmonic components in real time. The control strategy of the switching signals to compensate current harmonics of the three-phase inverter is also discussed and its switching signals are generated with the space voltage vector modulation scheme. The validity of this active filtering processing system to compensate current harmonics is substantiated on the basis of simulation results.

• Journal of the Korea Safety Management & Science
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• v.13 no.2
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• pp.147-155
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• 2011

For an effective energy management in intelligent buildings it is necessary to gather information about position/absence of people and the level of population. In this paper the smart occupancy detection system based on the active RFID is developed to satisfy such a demand. The performance of the developed system is tested and verified through various experiments. Furthermore the feasibility test of the active RFID tag is performed to verify whether it can be used as a location-based occupancy sensor. The developed core technology can be also applied to other fields such as security, healthcare, smart home, etc.

• Smart Structures and Systems
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• v.2 no.2
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• pp.171-188
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• 2006

This paper deals with damage detection using active Lamb waves. The wavelet transform and empirical mode decomposition methods are discussed for measuring the Lamb wave's arrival time of the group velocity. An experimental system to diagnose the damage in the composite plate is developed. A method to optimize this system is also given for practical applications of active Lamb waves, which involve optimal arrangement of the piezoelectric elements to produce single mode Lamb waves. In the paper, the single mode Lamb wave means that there exists no overlapping among different Lamb wave modes and the original Lamb wave signal with the boundary reflection signals. Based on this optimized PZT arrangement method, five damage localizations on different plates are completed and the results using wavelet transform and empirical mode decomposition methods are compared.