• Proceedings of the KSR Conference
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• 2007.11a
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• pp.792-800
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• 2007

The annual power cost for Seoul metro operations is about 65.5 billion won, of which rail motors account for 60% among total power consumptions. It is expected that the power consumption would increase because of global warming, future high electric equipments demands, etc. To reduce these consumptions, it is necessary to analyze the transportation demands of passengers, arrange the power-saving driving environments, respond flexible vehicles service, and improve how to drive vehicles. These method to reduce power consumption for rail motors can lead to improve the Seoul metro management. In this research, the improvement plan is derived by collecting and analyzing the data for total 33 power consumptions factors, screening top 10 factors by priority and impact, establishing each hypothesis to execute correlation and recursion analyses. As a result of 4 items research among top 10 affected factors, the power consumption for rail motors in 2006 is effectively reduced; the power usage is down with 13,870 kwh, from 531,539 kwh to 517,669 kwh, and the cost is down with 1,026 million won, from 39, 334 million won to 38,308 million won.

• Journal of KIISE:Information Networking
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• v.32 no.2
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• pp.180-189
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• 2005

This paper describes a transmission power control method for power saving in 802.11b wireless LANs. We have first explored how much effects reducing transmission power has on communication performance. Then we propose a power control algorithm, whose approach is similar to that of TCP congestion control, determining an appropriate transmission power level by monitoring the retransmission rate. We have implemented an utility software on a Linux-based system and made several experiments to validate the proposed method. The results show that it is possible to save energy consumption by controlling transmission power without sacrificing communication performance.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.15-22
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• 2019

In these days, importance of the power electronic devices and modules keeps increasing due to electric vehicles and energy saving requirements. However, current silicon-based power devices showed several limitations. Therefore, wide band gap (WBG) semiconductors such as SiC, GaN, and $Ga_2O_3$ have been developed to replace the silicon power devices. WBG devices show superior performances in terms of device operation in harsh environments such as higher temperatures, voltages and switching speed than silicon-based technology. In power devices, the reliability of the devices and module package is the critically important to guarantee the normal operation and lifetime of the devices. In this paper, we reviewed the recent trends of the power devices based on WBG semiconductors as well as expected future technology. We also presented an overview of the recent package module and fabrication technologies such as direct bonded copper and active metal brazing technology. In addition, the recent heat management technologies of the power modules, which should be improved due to the increased power density in high temperature environments, are described.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.5
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• pp.563-569
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• 2015

For some low-frequency applications such as power-related circuits, NEM relays have been known to show better performance than MOSFETs. For example, in a step-down charge pump circuit, the NEM relays showed much smaller layout area and better energy efficiency than MOSFETs. However, severe process variations of NEM relays hinder them from being widely used in various low-frequency applications. To mitigate the process-variation problems of NEM relays, in this paper, a new NEM-relay charge pump circuit with the self-adjustment is proposed. By self-adjusting a pulse amplitude voltage according to process variations, the power consumption can be saved by 4.6%, compared to the conventional scheme without the self-adjustment. This power saving can also be helpful in improving the power efficiency of the proposed scheme. From the circuit simulation of NEM-relay charge pump circuit, the efficiency of the proposed scheme is improved better by 4.1% than the conventional.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.136.1-136.1
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• 2011

This paper proposes the method to implement the railroad switching point heating system using the hybrid of the photovoltaic and wind power. The goal of the implementation of the railroad switching point heating system is to prevent freezing of the snow in the winter. The heating system of railway used to supply electricity through photovoltaic and wind power to prevent freezing. Hot wires of the railroad switching point heating system are used about 2kW of electric energy at the day. The electric energy of 2kW used the length of the hot wires about 3m. As the ON and/or OFF mode considering the tracks temperature and the ambient temperature, so the way the use of power-saving effect. In addition, the system can be used the railroad switching point heating system in winter and railway signal and street lights around the track in summer. In experiment, we acquired the power data according to time at the day of photovoltaic and wind power. We confirmed the temperature rise using the heating cable for 3m of $85^{\circ}C$, 30W/m. The temperature rise of the heating cable changes the temperature of $5^{\circ}C$ after 10 minutes and $11^{\circ}C$ after 10 minutes. We have confirmed the possibility of the railroad switching point heating system using the hybrid of the photovoltaic and wind power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6C
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• pp.603-613
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• 2006

Low-power design is one of the most important challenges encountered in maximizing battery life in portable devices as well as saving energy during system operation. In this paper we propose a low-power DCT (Discrete Cosine Transform) architecture using a modified Computation Sharing Multiplication (CSHM). The overall rate of Power consumption is reduced during DCT: the proposed architecture does not perform arithmetic operations on unnecessary bits during the Computation Sharing Multiplication calculations. Experimental results show that it is possible to reduce power dissipation up to about $7\sim8%$ without compromising the final DCT results. The proposed low-power DCT architecture can be applied to consumer electronics as well as portable multimedia systems requiring high throughput and low-power.

• Journal of the Korean Data and Information Science Society
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• v.22 no.4
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• pp.735-740
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• 2011

In recent, electronic devices were able to develop and focus for ultra-compact size, intelligence, multifunction and broadband. Their SMPS is realized to ultra-compact size, light weight, high efficiency, high reliability, low noises. The power module which can be used to supply DC output from a commercial power supply (85 to 265 VAC). A switching power supply can be made easily by adding simply external circuit, such as microcontroller, a relay, etc. It would be apply to mostly electronic devices, and fit the global project "Saving energy". But we need to statistical analysis for a quality and performance about a load and an output voltage in product.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9B
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• pp.1322-1329
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• 2010

As body sensor network (BSN) research becomes mature, the need for managing power consumption of sensor nodes has become evident since most of the applications are designed for continuous monitoring. Real time Electrocardiograph (ECG) analysis on sensor nodes is proposed as an optimal choice for saving power consumption by reducing data transmission overhead. Smart sensor nodes with the ability to categorize lately detected ECG cycles communicate with base station only when ECG cycles are classified as abnormal. In this paper, ECG classification algorithms are described, which categorize detected ECG cycles as normal or abnormal, or even more specific cardiac diseases. Our Euclidean distance (ED) based classification method is validated to be most power efficient and very accurate in determining normal or abnormal ECG cycles. A close comparison of power efficiency and classification accuracy between our ED classification algorithm and generalized linear model (GLM) based classification algorithm is provided. Through experiments we show that, CPU cycle power consumption of ED based classification algorithm can be reduced by 31.21% and overall power consumption can be reduced by 13.63% at most when compared with GLM based method. The accuracy of detecting NSR, APC, PVC, SVT, VT, and VF using GLM based method range from 55% to 99% meanwhile, we show that the accuracy of detecting normal and abnormal ECG cycles using our ED based method is higher than 86%.

• Journal of Navigation and Port Research
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• v.32 no.10
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• pp.765-770
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• 2008

This paper presents the power control for the hybrid electric propulsion system. In this paper, the hybrid propulsion system consists cf the generator and battery as power supply system in ship. The hybrid control system is designed with energy saving algorithm for decreasing the power consumption of power supply system. This paper suggests the method to increase efficiency of hybrid electric propulsion system by developing battery charging system. The performance of power control system is analyzed with the experiment equipment for hybrid propulsion system, and the results showed a good property.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.1
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• pp.93-99
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• 2021

The government has proposed a mission to enhance intelligent power networks, decrease coal-fired generation, expand distributed energy resources, and promote energy prosumer into the distribution network in Korea. Installation cost of facility expansion to guaranteed interconnection with small distributed energy resources increases dramatically on KEPCO's distribution sector. And it is hard to withdraw in time. In addition, there are explicit research is required to meet the reliability on grid corresponding to the increase of distributed power. Infrastructure support for accommodating energy prosumer is also needed. Therefore, KEPCO is pushing transition to DSO by expanding distribution management scope and changing its roles. In addition, KEPCO is proactively preparing for integrated operation between distribution network and existing distributed power which is accommodated passively. KEPCO is also trying to accept multiple network users, e.g. building platforms, to manage a data and promote new markets. In the long term, transition to DSO will achieve saving investment costs for accommodating distributed sources and maintaining stable electrical quality. And it will be possible to create new business model using the platform to secure revenue.