• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.7
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• pp.587-595
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• 2006

A system operating algorithm was developed for the effective operation of a multi-type air-conditioning system. The system operating algorithm includes control algorithms for a safety mode, an initial operating mode, a stabilization mode, a fault diagnosis mode, an efficiency mode, and a tracking mode. Various tests were performed to show the effectiveness of these algorithms. Tests showed good results for the operation of a multi-type air-conditioning system. Therefore, these algorithms developed for this study may be used for the effective control of a multi-type air-conditioning system.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1142-1152
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• 2019

This paper presents a control method for reducing the current distortion in an indirect matrix converter (IMC) operating in boost mode under unbalanced input conditions. IMCs operating in boost mode are useful in distributed generation (DG) systems. They are connected with renewable energy systems (RESs) and the grid to transmit the power generated by the RES. However, under unbalanced voltage conditions of the RES, which is connected with the input stage of the IMC operating in boost mode, the input-output currents are distorted. In particular, the output current distortions cause a ripple of the power, which is transferred to the grid. This aggravates the reliability and stability of the DG system. Therefore, in this paper, a control method using positive/negative sequence voltages and currents is proposed for reducing the current distortion of both side in IMCs operating in boost mode. Simulation and experimental results have been presented to validate effectiveness of the proposed control method.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.3
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• pp.311-317
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• 1997

DTG(dynamically tuned gyroscope) is a sensor detecting disturbance in angle velocity control loop of EOTS(electro optical tracking system), which is used for the stabilization of gimbal. DTG is classified into rate mode or rate integrated mode according to operating mode. In this paper, basic principles and characteristics of DTG, depending on to operating mode, are compared and the model of rate integrated mode DTG is proposed. Also, the validity of the presented model is verified by computer simulations and experiments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.4
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• pp.444-450
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• 2013

This paper presents the criteria for setting the dynamic operating mode of BESS(Battery Energy Storage System) in the bulk power systems. ESS has been expected to improve the degraded dynamic performance of the power system with high penetration of the renewable resources. While ESS is controlled in steady state or dynamic operating mode for its better effectiveness depending on the operating conditions of power systems, the criteria for setting the dynamic operating mode for the transient period needs to be robust enough to cover all the different conditions. The proposed criteria consider the varying conditions and the operating practices of the bulk power systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.5
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• pp.314-320
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• 2008

The cooling load in winter is significant in buildings and hotels because of the usage of office equipments and the improved wall insulation. Hence, a multi~heat pump is required to cover heating and cooling simultaneously for each indoor unit. In this study, the operating characteristics and performance of a simultaneous heating and cooling heat pump in the cooling-main operating mode were investigated experimentally. The system adopted a variable speed compressor using R410A with four indoor units and one outdoor unit. In the cooling-main mode, the heating capacity decreased due to reduction of flow rate to the indoor unit under heating mode operation. The EEV opening was adjusted to increase flow rate to the indoor unit under heating mode operation. The total capacity and COP in the cooling-main mode increased by 20.5% and 29.2%, respectively, compared with those in the cooling-only mode.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.7
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• pp.1-7
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• 2010

The device performances of accumulation-mode Pi-gate pMOSFETs with different fin widths have been characterized at high operating temperatures. The device fin height is 10nm and fin widths are 30nm, 40nm, and 50nm. The variation of the drain current, threshold voltage, subthreshold swing, effective mobility, and leakage current have been investigated as a function of operating temperatures. The drain current at high temperature is slightly larger than at room temperature. The variation of the threshold voltage as a function of the operating temperature is smaller than that of the inversion-mode MOSFETs. The effective mobility is decreased with the increase of operating temperature. It is observed that the effective mobility is enhanced as the fin width decreases.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.11
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• pp.1410-1416
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• 1999

This paper aims at investigating the operating-mode characteristics of two-module Thyristor Controlled Series Compensator (TCSC) as an equivalent of the multi-module TCSC in a simple three-phase power transmission system. The load flow program is developed to analyze the steady-state characteristics of two-module TCSC system and to find the thyristor firing angles for the required real power flow. The stability calculation program is developed with Poincare mapping theory. Simulation studies of the TCSC power transmission system using EMTP are performed to evaluate the transient characteristics of two-module TCSC as a real power flow controller and to rpove the results of the load flow calculation and the stability analysis. In the process of the study, the operating-mode characteristics of two-module TCSC are evaluated and compared to those of single-module TCSC.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.206-209
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• 2004

We investigated response characteristics of liquid crystal display(LCD) with different operating mode of nematic liquid crystals (NLCs) such as $45^{\circ}$twist nematic (TN), $67.3^{\circ}$TN and ECB(electrical controlled birefringence) on a rubbed polyimide (PI) surface. The three kinds of LCD operating mode obtain stable EO performance. Low transmittances of the $45^{\circ}$TN and $67.3^{\circ}$TN cell on the rubbed PI surface were achieved by using low cell gap d. The fast response time of ECB cell among the three kinds of LCD operating mode was measured.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.416-421
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• 2009

Recently, the new Korean Tilting Train Express(TTX) which maintains a speed on the curve railway line is developed. Electric railways, including the TTX, have electrical problems that could bring about serious accidents. For such reasons, the electric railway's electrical problems, electrical harmonic and others, have been studied briskly. Thus, TTX's electrical problems also need leading studies because the new Korean TTX will operate earnestly in 2012. The results could be used hereafter diagnosis of it's components and train conditions. In the paper, electrical signals in TTX operation were measured to analyze electrical harmonic. In addition, after the electrical signals were measured to operating mode (coasting mode, acceleration mode and regenerative breaking mode) respectively in test section(Ho-nam line, Chung-buk line, Jung-ang line and Tae-baek line). The electrical harmonics considered operating modes triparted were analysed and evaluated.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.245-250
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• 2017

Worldwide environmental regulations have been enhanced for emission reduction of greenhouse gases and air pollutants; accordingly, some measures were prepared. Furthermore, the need for effective and reasonable energy-saving methods is growing in accordance with that for environmental pollution minimization. In the case of marine engineering, techniques for the development of eco-friendly vessels have been actively studied, including reduction of exhaust gas emissions, development of alternative fuel, and development of a new propulsion system. In this study, we presented the basic concepts and analyzed the speed, current, voltage, and output power characteristics of each operating mode, i.e., operating mode of battery, generator, and full power.