• Journal of Industrial Technology
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• v.27 no.B
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• pp.21-27
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• 2007

The power line channel has time-variant characteristics caused by various kind of electrical devices. This characteristics are synchronized with the main voltage by their own characteristics. The main factors of disturbance are the variation of the channel impedance and noises. In other papers, the synchronous noise modeling has been achieved. But the modeling is not satisfied simultaneously with the time domain and the frequency domain and there are not any discussion about short-term variations of the channel impedance which cause to the signal fading. Therefore, this paper researched to solve problems about the signal fading by analyzing the short-term variation of the channel impedance, and proposed the synchronous noise modeling which is satisfied simultaneously in the time domain and the frequency domain.

• Journal of electromagnetic engineering and science
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• v.15 no.1
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• pp.26-30
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• 2015

In this paper, a simple equivalent circuit model for a defected ground structure (DGS) microstrip line with stepped impedance slot-lines in the ground plane is presented. In addition, an analytic expression for the resonance frequency of the proposed structure is derived. In equivalent circuit modeling, the capacitance and the inductance of the resonance circuit are evaluated from the dimensions of the etched pattern in the ground plane. The resonance frequencies calculated from the proposed method are compared with those obtained with an electromagnetic (EM) simulation.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.585-592
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• 2003

The parallel operation system of UPS is used to increase reliability of power source at critical load. But parallel UPS system has a few defects, impedance is different from each other and circulating current occurs between UPSs, due to line impedance and parameter variation, though controlled by the same synchronization signal. According to such characteristic of parallel UPS, balanced load-sharing control is the most important technique in parallel UPS operation. In this paper, a novel power deviation compensation algorithm is proposed. it is composed of voltage controller to compensate power deviation that be calculated by using active and reactive current deviation between Inverters on synchronous d-q reference frame.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.293-299
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• 2012

Electrical impedance tomography is an imaging modality for determining the electrical properties inside a domain. Small currents are injected and the resulting voltages are measured through the electrodes. The internal electrical properties are reconstructed based on these voltage and current data. In this paper, a novel on-line Landweber algorithm was developed to fast estimate the resistivity distribution in the inverse calculation. Additionally, to enhance the reconstruction performance, a step-length was computed from the eigenvalue of the weighting matrix. The numerical experiments have been performed to evaluate the reconstruction performance of the proposed method.

• International Journal of Internet, Broadcasting and Communication
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• v.10 no.3
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• pp.109-114
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• 2018

In order to improve performance for the size of the BLPD, the CCL is used for the realization as the delay line. As realizing lower coupling coefficient and lower characteristic impedance, the CCL has good performance of the phase delay. The CCL is applied as the compact BLPD with optimized coupling factor and matched impedance because the lower coupling coefficient and lower characteristic impedance are increased the size and the loss, respectively. Designed BLPD using the CCL has the size of $0.13{\lambda}_g{\times}0.13{\lambda}_g$ and the size-reduction ratio of fabricated BLPD using the CCL has 58.5% ($21.08{\times}21.40mm^2$). Also, fabricated BLPD is measured the insertion loss of 3.16dB at the center frequency of 1.78GHz and the 20dB bandwidth is 9.58%. Differenced magnitude and phase between threw port and coupled port are measured 0.1dB and $89.9^{\circ}$, respectively. These performances are almost same compared with the conventional BLPD. Suggested application of the CCL can be used various devices and circuits for the size-reduction.

• Journal of Advanced Navigation Technology
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• v.20 no.4
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• pp.361-366
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• 2016

This paper presents an arbitrary impedance transformer with unequal split, based on S- to admittance parameter conversion. When compared even/ odd- mode analysis, the parameter conversion design method constitutes a simple design method to include phase delay information and arbitrary port impedances and asymmetrical configurations. To validate this design method, we designed a 50 to $12.5{\Omega}$ impedance transformer with a 3:1 unequal power split, at an operating frequency of 1 GHz. To implement the proposed impedance transformer, the low impedance transmission lines of calculated result are fabricated by the transmission line connected shunt open stub. Good experimental performances were obtained, in full agreement with simulated results.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1274-1279
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• 2004

This paper proposes technique to detect ground fault in railway high voltage distribution lines. Overcurrent relay technique is widely used for detecting one line ground fault that occurs most frequently in railway high voltage distribution lines. However, ground fault in distribution line is usually high impedance fault with arc. Because the fault current magnitude measured in substation is very small, the conventional overcurrent relay can't detect the high impedance ground fault. Therefore this paper proposes the advanced technique using wavelet transform. It extracts D1 component from fault signals and detects fault comparing magnitude of D1 component in each phase. To evaluate this proposed technique, we model distribution system using PSCAD/EMTDC and extract various fault data. In conclusion this technique can detect ground fault including high impedance fault regardless of fault distance, fault impedance etc.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.897-899
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• 1997

The analysis of distribution line faults is essential to the proper protections of the power system. A high impedance fault does not make enough current to cause conventional protective devices. It is well known that undesirable operating conditions and certain types of faults on electric distribution feeders cannot be detected by using conventional protection system. This paper describes an algorithm using back-propagation neural network for pattern recognition and detection of high impedance faults. Fractal dimensions are estimated for distinction between random noise and chaotic behavior in the power system. The fractal dimension of the line current is also used as a indication of the high impedance fault.

• International Journal of Railway
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• v.3 no.2
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• pp.46-53
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• 2010

Electric railroad systems consist of rolling stock, track, signal and catenary system. In the catenary system, one of the most important factors is the impedance according to the design and characteristic. Before the catenary system is designed, the impedance should be precedently researched. The railroad catenary system is complex system which is composed by five conductors. The five conductors classify up and down feeders, up and down contact wire group, rail group. Therefore, we should compose the catenary system of the equivalent five-conductors model. In this paper, we suggest a geometrical model and a equivalent conductor model by using geometric mean radius of five conductors in the catenary system. Also, we calculate demanded parameter values in the model. By using those, line constants of five conductors are analyzed by applying the equivalent method called as the condensed joint matrix.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.3
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• pp.367-376
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• 2012

This paper describes a Adaptive Impedance Tuning Circuit which can be adaptively tuned between circuit's characteristic impedance and the arbitrary load impedance. The Adaptive Impedance Tuning Circuit is consisted of such parts as mismatch sensor, impedance tuner and tuning algorithm. Each parts's design methods proposed in other papers are compared with their advantages and disadvantages. And we propose simple design method for Adaptive Impedance Tuning Circuit using a ${\lambda}/4$ transmission line and ${\pi}$-network. Calculation formulas and selection algorithm from calculated values of a complex load impedance are proposed and simulation using induced calculation formulas and selection algorithm is performed. Simulation results show good agreement with theoretical predictions.