• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.533-539
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• 2018

In this paper, the transformer type superconducting fault current limiter (SFCL) with additionally coupled circuit was suggested and its peak fault current limiting characteristics due to the fault condition to affect the fault current were analyzed through the fault current limiting tests. The suggested transformer type SFCL is basically identical to the previous transformer type SFCL except for the additional coupled circuit. The additional coupled circuit, which consists of the magnetically coupled winding to the primary and the secondary windings together with another superconducting element and is connected in parallel with the secondary winding of the transformer type SFCL, is contributed to the peak fault current limiting operation for the larger transient fault current directly after the fault occurrence. To confirm the fault current limiting operation of the suggested SFCL, the fault current limiting tests of the suggested SFCL were performed and its effective peak fault current limiting characteristics were analyzed through the analysis on the electrical equivalent circuit.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.877-882
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• 2005

The definition of multi-coupled operation is that coupled two trainsets is able to be operated one trainset identically. That is to say, the one driver, coupled two trainsets can operate the traction and braking system, control vehicle doors, phanto-graph, HVAC and passenger room lighting system etc, such as one trainset controlling. This study will provide high speed train design engineer with introducing multi-coupled operation system electrically and presentation automatic complex coupler mechanism, and then this paper will be applied to design next generation high speed train system such as Jun-la/Ho-nam line

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.330-331
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• 2011

The interleaving method is usually used to reduce the ripple of output current of filter inductor in parallel operation of PWM DC/DC converter. Although the current ripple of filter inductor decreases, each current ripple of filter inductor is not decreased. In this study, the operation of interleaved buck converter with coupled inductor is analyzed in each operation mode. It is verified through experiment. The possibility of application to grid connected inverter with parallel operation is identified.

• Journal of Power Electronics
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• v.14 no.5
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• pp.827-833
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• 2014

This study proposes a coupled inductor method for the parallel operation of a power conditioning system (PCS). When primary and secondary currents flow in the same direction in a coupled inductor, total flux and inductance are cancelled; when currents flow in opposite directions, each flux becomes an individual inductor. These characteristics are applied in the parallel operation of a PCS. To connect at a grid code, abnormal current, which is barred under the grid connection code, is blocked by using a coupled inductor. A design based on the capacity and current duration time of a PCS is verified through hardware implementation. Experiment results show the effectiveness of variance reduction.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1428-1432
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• 2007

One of the most important targets of transportation is to transport human and commodities to the destination safely. Railway has low risk, compared with land, ocean and flight route and it assures high security as well as high speed driving, since it runs on regular track. However, train accident may result in tragic accident due to small carelessness, so special event recorder is preferably used in order for clarity of responsibility in case of accident, maintenance of signal device and defect analysis. JRU(Juridical Recorder Unit) for ATC/ATS/ATP can be more advanced event recorder. Event recorder of KTX-I which is running now is installed one by one on each leading car and last car, and operation plan of event recorder in case of single trainset is suggested. But regarding train operation of multi-coupled trainset operation such as KTX-II, more detailed study is required for event recorder revitalization and record data process method. Therefore, this research aims at operation plan used in existing event recorder, and suggests effective operation and management plan of event recorder in multi-coupled trainset such as new High Speed Train.

• Journal of Power Electronics
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• v.18 no.3
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• pp.879-891
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• 2018

A bidirectional dc-dc converter is used in battery energy storage systems owing to the growing requirements of a charging and discharging mode of battery. The magnetic coupling of output or input inductors in parallel-connected multi modules of a bidirectional dc-dc converter is often utilized to reduce the peak-to-peak ripple size of the inductor current. This study proposes a novel design guideline to achieve minimal ripple size of the inductor current under bidirectional power flow. The newly proposed design guideline of optimized coupling factor is applicable to the buck and boost operation modes of a bidirectional dc-dc converter. Therefore, the coupling factor value of the coupled inductor does not have to be optimized separately for buck and boost operation modes. This new observation is explained using the theoretical model of coupled inductor and confirmed through simulation and experimental test.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.1
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• pp.43-50
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• 2009

The characteristics at the intermediate operation point of the turbopump-gas generator(TP-GG) coupled test were investigated by analytical method. The pump outlet pressure, gas generator mixture ratio, gas generator pressure, and temperature were examined considering risk minimization of test. The engine system shows different behavior from the TP-GG coupled test at the intermediate operation point since the combustion pressure feeds back to the flow rate in the lines. The advanced valve changes in the combustor line helps less risky mode transition.

• Journal of Power Electronics
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• v.18 no.1
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• pp.11-22
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• 2018

This paper presents a single switch, high step-up, non-isolated dc-dc converter suitable for renewable energy applications. The proposed converter is composed of a coupled inductor, a passive clamp circuit, a switched capacitor and voltage lift circuits. The passive clamp recovers the leakage inductance energy of the coupled inductor and limits the voltage spike on the switch. The configuration of the passive clamp and switched capacitor circuit increases the voltage gain. A wide continuous conduction mode (CCM) operation range, a low turn ratio for the coupled inductor, low voltage stress on the switch, switch turn on under almost zero current switching (ZCS), low voltage stress on the diodes, leakage inductance energy recovery, high efficiency and a high voltage gain without a large duty cycle are the benefits of this converter. The steady state operation of the converter in the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is discussed and analyzed. A 200W prototype converter with a 28V input and a 380V output voltage is implemented and tested to verify the theoretical analysis.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.6
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• pp.437-445
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• 2021

This paper proposes an operating frequency design method that limits the voltage applied to aload-side converter during the initial operation of a loosely coupled resonant dual-active bridge (LCR-DAB) converter and an initial operating strategy that applies it. The LCR-DAB converter uses two wireless power transfer coils instead of the high-frequency transformer of the general DAB converter. The wireless power coil has a physical distance of several tens of millimeter or more between the two coils; thus, the LCR-DAB converter is a bidirectional isolated power conversion system that can easily achieve high insulation performance. However, for the initial operation of the LCR-DAB, if the power-side converter is operated at the resonance frequency while the load-side converter is not operating, then a very high voltage due to resonance is applied to the load-side converter, thereby causing damage to the converter. Therefore, a method that can stably charge the DC link voltage of the secondary-side converter during the initial operation is needed. This paper proposes a method to initially charge the secondary-side DC link by operating the primary-side converter at a frequency with limited voltage gain rather than at a steady-state operating frequency. The validity of the proposed frequency design method and initial operating sequence is verified through simulation and experimentation of the 1 KW LCR-DAB converter.

• ETRI Journal
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• v.27 no.5
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• pp.643-646
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• 2005

This letter proposes a band-pass filter (BPF) with two transmission zeros based on a combination of parallel coupling and end coupling of half-wave transmission lines. The fabricated BPF exhibited a narrow bandwidth and two transmission zeros near the pass-band due to the end-coupled and shielding waveguide. At the center operation frequency of 60 GHz, the 20 dB bandwidth of the BPF is 1.0 GHz, which is almost 2% of the center operation frequency, and the insertion loss is 3.12 dB. Two transmission zeros reach approximately 40 dB at 58.5 and 62.5 GHz. The simulation results almost agree with the measured results.