• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.6
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• pp.749-756
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• 2015

In this paper, we propose a unique systolic structure and communication algorithm that maintains a solid link between nodes using synchronous digital communication and enables low power communication. This system was designed by using CC2500 RF transceiver, CC2590 RF front end and C8051F330 low power microcontroller. The measurement of power consumption in the network link shows below $400{\mu}W$ in data transfer rate 320bps. The system constitutes the base unit of low power wireless network that was composed of each seven link nodes having eight sensor nodes. Results of the experiments show that link nodes using a 4Ah battery could operate over 3 years without replacement.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1447-1453
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• 2014

This paper proposes the new method based on the availability of three points measurement and convexity of photovoltaic (PV) curve characteristic at the maximum power point (MPP). In general, the MPP tracking (MPPT) function is the important part of all PV systems due to their power-voltage (P-V) characteristics related with weather conditions. Then, the analog-to-digital converter (ADC) and low pass filter (LPF) are required to measure the voltage and current for MPPT by the digital controller, which is used to implement the PV power conditioning system (PCS). The measurement and quantization error due to rounding or truncation in ADC and the delay of LPF might degrade the reliability of MPPT. To overcome this limitation, the proposed method is proposed while improving the performances in both steady-state and dynamic responses based on the detailed investigation of its properties for availability and convexity. The performances of proposed method are evaluated with the several case studies by the PSCAD/EMTDC$^{(R)}$ simulation. Then, the experimental results are given to verify its feasibility in real-time.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.45-53
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• 2013

In this paper, we analyze the typical phase voltage and line current waveform characteristics of the distribution system with 3 phase small synchronous generation source in case with load and non-load group, in order to investigate the power quality for end load connected of generation source. As demonstrated by our experimental results, the distortion and power quality of phase voltage and line current waveform were relatively good for low voltage 3 phase model grids connected of 3 phase small synchronous generation source in case with non-load group. However, distortion and power quality of voltage and current waveform was poor for low voltage 3 phase model grids connected to 3 phase small synchronous generation source in the load group with some phase voltage and frequency difference. From the above results, we conclude that the phase voltage and frequency of 3 phase generation source must be identical to that of distribution system source to maximize the power quality. Also, special attention is required in case of having load group or non-load group to 3 phase generation source.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.7
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• pp.364-369
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• 2002

In this paper, 3-D magnetostatic finite element simulation of a rotux type Low-Tc superconducing (LTS) superconducting power supply, finite element method, cryogenic system, superconducting foil by generated magnetic flux from the rotating pole. The magnetic flux density on the superconducting foil caused by two exciters is therefore sufficiently greater than its critical magnetic flux density and it is an essential point in LTS power supply design. To establish the sufficient flux path of this machine, ferromagnetic materials is used in this power supply. When ferromagnetic materials is used at extremely low temperature, its characteristic of magnetization differs to that at room temperature. For this reason, special consideration is needed in the magnetic analysis of cryogenic systems. When the excitation current is 10A, the normal spot appears on superconducting foil. The results of this analysis are calculated and compared with the experimental results. The linkage flux due to the excitation current of 10, 20, 30, 40 and 50A are respectively $1.30{\times}10-4$, $2.67{\times}10-4$, $5.08{\times}10-4$ and $6.15{\times}10-4Wb$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4C
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• pp.401-407
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• 2010

In this paper, we consider a low-complex companding technique for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems. For the technique, we propose a novel companding function to compensate the problem of the conventional companding functions which are difficult to design complying with system requirements and deteriorate the bit error rate (BER) performance significantly. The proposed scalable companding function can provide an arbitrary value of the maximum PAPR with which the BER performance changes gracefully. In addition, the proposed companding function can be designed readily according to the PAPR and BER performance required by the system and is observed to provide better BER performance than the conventional clipping and $\mu$-low companding schemes under the similar PAPR condition.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.458-461
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• 2009

In 3-phase 4 wire system, appearance of the $3^{rd}$ harmonic current by increasing non-liner load is the one of causes overheating neutral wire of power line, and apparatus. So it is necessary to protect power-factor decreasing by the $3^{rd}$ harmonic, and electric power apparatus, and line safely, in this study, power system accidents caused by the $3^{rd}$ harmonic were investigated, then harmonic components analysis and unbalanced load analysis got accomplished. As result, we proposed the method to protect the power line and apparatus from over-current of neutral line by using the most economic 4-pole low voltage circuit breaker.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.8
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• pp.1465-1470
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• 2006

This paper presents a design of low power CMOS LNA(Low Noise Amplifier) for 2.4 GHz ZigBee applications that is a promising international standard for short area wireless communications. The proposed circuit has been designed using TSMC $0.18{\mu}m$ CMOS process technology and two stage cascade topology by current reuse technique. Two stage cascade amplifiers use the same bias current in the current reused stage which leads to the reduction of the power dissipation. LNA design procedures and the simulation results using ADS(Advanced Design System) are presented in this paper. Simulation results show that the LNA has a extremely low power dissipation of 1.38mW with a supply voltage of 1.0V. This is the lowest value among LNAs ever reported. The LNA also has a maximum gain of 13.38dB, input return loss of -20.37dB, output return loss of -22.48dB and minimum noise figure of 1.13dB.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.553-555
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• 1996

This paper concerns with a method to improve the current and power waveforms of the variable speed $3{\Phi}$ AC motor system driven by the single-pulse PWM, and the current waveforms and $3{\Phi}$ power waveforms are analyzed by FFT under various running conditions. By the performance analysis through the experiments, the following results have been obtained. AC source of pseudo sine waveform can be obtained from the modulated alternating square voltage by means of the well designed LC filter. It is confirmed that current waveforms and $3{\Phi}$ power waveforms can be improved by utilizing the high order low pass LC filter than that of lower order. Especially, current waveforms and $3{\Phi}$ power waveforms tan be much improved at low frequency domain. $3{\Phi}$ power waveforms have a smatter ripple and bigger power by utilizing the high order low pass LC filter than that of lower order. Also, the running condition of $3{\Phi}$ AC motor is good at low frequency domain.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1061-1063
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• 2001

This paper proposes a new power conditioning system for the SMES composed of a thyristor PWM converter with a resonant commutation circuit. The operation of the proposed system and the dynamic interaction between SMES and the power system is analyzed by a theoretical approach with equivalent circuits and verified by computer simulations with EMTP, considering a typical 154kV power system. The proposed system can provide a solution for the power factor regulation and harmonic level reduction in the ac terminal with low-cost system configuration.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.6
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• pp.293-299
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• 2001

This paper proposes a new power conditioning system for the SMES composed of a thyristor PWM converter with a resonant commutation circuit. The operation of the proposed system and the dynamic interaction between SMES and the power system is analyzed by a theoretical approach with equivalent circuits and verified by computer simulations with EMTP, considering a typical 154kV power system. The proposed system can provide a solution for the power factor regulation and harmonic level reduction in the ac terminal with low-cost system configuration.