• 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 Power Electronics
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• v.3 no.1
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• pp.49-54
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• 2003

A novel control scheme of using a single electronic drive to synchronize two synchronous motors is investigated analytically. The developed control strategy extends the conventional vector control technology, Specifically, it utilizes the property that the motion of two motors can be independently controlled by the q-axis currents provided the desired q-axis currents can be achieved by adjusting physical armature currents. The latter part is indeed guaranteed by adding a position offset to one of the motors. This work has a potential of cost saving in practice where the cost of drive is a major concern.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.260-265
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• 2001

This paper describes total flow control of an ice slurry system for pump energy saving. Similar turbo machinery has a characteristic that input power ratio is proportional to the three time of revolution speed ratio. To reduce the energy cost of brine pump in ice slurry storage systems, inverter is adapted instead of 3-way valve to control the speed of brine pump motor. One type of cooling load profile was used as driving load of the system, generated by a boiler and warm water storage tank. As results of the laboratory test, energy consumption and cost of the pump were reduced by 11.4%.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.202-207
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• 2014

Recently, the study of energy saving technology of ships begins in earnest, as energy saving policies are performed all around the world. SEMS (Ship Energy Management System) is one of the techniques to increase energy efficiency by applying to a independent system like a ship and offshore. SEMS is composed of Cooling Pump Control System (CPCS), Renewable Energy Emergency Power Control System (REEPCS), Load Control System (LCS), and Heating, Ventilation, and Air Conditioning System (HVACS). SEMS is enable to increase energy efficiency and achieve integrated management through the interlocking of each system. Especially, it is possible to improve the flexibility of the selection of the generator capacity in conjunction with a rechargeable battery and renewable energy. In this paper, SEMS applied rechargeable battery is proposed and simulated. By applying the rechargeable battery, it was confirmed that SEMS applied rechargeable battery can be operated at optimum efficiency of the generator.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1643-1653
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• 2014

This paper presents the design and implementation of a wind-solar hybrid power system for LED street lighting and an isolated power system. The proposed system consists of photovoltaic modules, a wind generator, a storage system (battery), LED lighting, and the controller, which can manage the power and system operation. This controller has the functions of maximum power point tracking (MPPT) for the wind and solar power, effective charging/discharging for the storage system, LED dimming control for saving energy, and remote data logging for monitoring the performance and maintenance. The proposed system was analyzed in regard to the operation status of the hybrid input power and the battery voltage using a PSIM simulation. In addition, the characteristics of the proposed system's output were analyzed through experimental verification. A prototype was also developed which uses 300[W] of wind power, 200[W] of solar power, 60[W] LED lighting, and a 24[V]/80[Ah] battery. The control system principles and design scheme of the hardware and software are presented.

• Transactions of The Korea Fluid Power Systems Society
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• v.7 no.3
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• pp.1-6
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• 2010

This paper deals with the issue of simple adaptive position control for a pump-controlled cylinder system. A fixed displacement pump is utilized instead of servo valve and its speed is controlled by AC motor. The whole control system is composed of a pair of interconnected subsystems, that is, a feedback control system and a feedforward control system. From experiments it is shown that position control using simple adaptive control can accomplish significant reduction in position tracking error comparing to a conventional PID control.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.11
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• pp.1900-1906
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• 2016

Recent energy efficiency policy of green growth for stable power supply is required. Urban transit vehicles is limited to reduce the use of power without reducing the number of runs. Accordingly, when urban rail vehicles is braking, the occurrence of regenerative power is systemically maximized for the purpose of saving energy. As a result when it is braking, the generated power efficiently is used and looking for a way to reduce the electrical energy. In this paper, the brake control system of the Subway Line 3 is analyzed the effect to meet the required regenerative braking produced electricity through minimizing air braking force of service braking.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.86-87
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• 2009

LED backlight for LCD TV is a great alternative to CCFL backlight due to its low power consumption and flexible arrangement. Various LED backlight configurations are being used to control the backlight locally in order to achieve both power efficiency and high contrast. However, the relatively small spatial resolution of the backlight system results in showing artifacts of backlight control that is acknowledgeable to human vision. Moreover, such artifacts get worse between temporal frames. In this paper we present a method of decreasing such temporal artifacts with a Human Visual System(HVS) approach to minimize distortion caused by local backlight dimming.

• Journal of the Korean Society of Industry Convergence
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• v.9 no.1
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• pp.79-86
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• 2006

In this study, we research and develope Intelligent Remote management controller. According to the load condition, we will apply various control techniques and plan high efficient Demand control. After development, According to the Demand Control, An electricity enterprisers will expect enlargement of equipment coefficient, elevation of back up load factor and reduction effect of equipment investment. On Customer side, They will expect reduction of electric fee, saving energy and variety of service choice.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.7
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• pp.380-388
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• 2006

In this paper, a novel control algorithm to minimize the power loss of the induction generator for wind power generation system is presented. The proposed method is based on the flux level reduction, where the flux level is computed from the machine model for the optimum d-axis current of the generator. For the vector-controlled induction generator, the d-axis current controls the excitation level in order to minimize the generator loss while the q-axis current controls the generator torque, by which the speed of the induction generator is controlled according to the variation of the wind speed in order to produce the maximum output power. Wind turbine simulator has been implemented in laboratory to validate the theoretical development. The experimental results show that the loss minimization process is more effective at low wind speed and that the percent of power loss saving can approach to 25%. Experimental results are shown to verify the validity of the proposed scheme.