• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.2
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• pp.224-229
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• 2014

This paper presents the novel voltage control method in power distribution system with distributed generators. The voltage in distribution systems is regulated by Under Load Tap Changer(ULTC) of substation and pole transformer of primary feeders. Recently, Step Voltage Regulator(SVR) is getting located at distribution feeders to regulate effectively voltage of primary feeders. But the effectiveness of SVR decreases due to independent operation between SVR and ULTC, and also the existing Line Drop Compensator(LDC) method considering the distributed generators may be not able to regulate the proper voltage in a permissible range. Thus, this paper presents a optimal voltage control algorithm of SVR by using the secondary voltage data of main transformer in substation.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.772-774
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• 2005

Interstate electric power system, as an alternative for energy cooperation under regional economic bloc, has been hotly debated before progressing the restructure in electric power industry and rapidly expanded in many regions after 1990s. Especially, since northeast asia has strong supplementation in resource, load shape, fuel mix etc., electric power system interconnection in this region may bring considerable economic benefits. Moreover, since Korean electric power system has a great difficulty in a geographical condition to interrupt electricity transaction with other countries, it has been expanded as an independent system to supply all demand domestically. As a result, Korean electric power system makes considerable payment for maintaining system security and reliability and expands costly facilities to supply a temporary summer peak demand. Under this inefficiency, if there are electricity transactions with Russia via the North Korea route then economic electric power system operation may be achieved using seasonal and hourly differences in electricity price and/or load pattern among these countries. In this paper, we estimate price cap of transacted electricity via interstate electric power system in northeast asia. For this study, we perform quantitative economic analysis on various system interconnection scenarios.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.2
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• pp.94-99
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• 2018

Depending on how the energy storage system(ESS) is used in a system that can construct a microgrid by using an independent power source such as campus, surplus power can be generated that can not be charged to the ESS. For example, assuming that heat is supplied by a fuel cell in the case of a system in which thermal self-sustaining is prioritized, the fuel cell capacity required differs depending on the heat load. The amount of surplus power that can not be stored in the ESS will appear differently depending on the load operation of the fuel cell for each cycle. This power is hydrogenated through a water electrolytic device to present the amount of hydrogen energy that can be operated for each cycle. Therefore, this paper propose the possibility of utilizing University campus as a hydrogen station.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.3
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• pp.128-132
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• 2006

Interstate electric power system, as an alternative for energy cooperation under regional economic bloc, has been hotly debated before progressing the restructure in electric power industry and rapidly expanded in many regions after 1990s. Especially, since northeast asia has strong supplementation in resource, load shape, fuel mix etc., electric power system interconnection in this region may bring considerable economic benefits. Moreover, since Korean electric power system has a great difficulty in a geographical condition to interrupt electricity transaction with other countries, it has been expanded as an independent system to supply all demand domestically. As a result, Korean electric power system makes considerable payment for maintaining system security and reliability and expands costly facilities to supply a temporary summer peak demand. Under this inefficiency, if there are electricity transactions with Russia via the North Korea route then economic electric power system operation nay be achieved using seasonal and hourly differences in electricity price and/or load pattern among these countries. In this paper, we estimate price cap of transacted electricity via interstate electric power system in northeast asia. For this study, we perform quantitative economic analysis on various system interconnection scenarios.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.8
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• pp.932-940
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• 1999

This paper discusses the development of an interactive and graphic software for the education and training of power system operation and control, especially for students and beginners. This software has a lot of functions for users to simulate the power system operation and control with ease. These functions included in this software are followings. First, this software includes a Graphic User Interface (GUI) - which contains interactive simulation scheme, Windows dialog box, graphic representations, and graphic icons - so that users can handle the software in user-friendly environments. Second, it uses a graphic editor so that users can easily edit the one-line diagram of the power system. Third, it prepares a database system so that users can manage the power system data for simulation easily. Fourth, the application modules included in the software are the Economic Dispatch (ED) and the Automatic Load-Frequency Control (ALFC). These application modules are designed as independent modules. Using the ED module, users can understand the basic concepts of the ED with ease. And using the ALFC module, they can easily acquire the basic understanding of the response of the ALFC between the two-area systems. The proposed software is tested on both the 16 bus and the two-area sample system. The test has confirmed the functions of the developed software. It is anticipated that the software will be useful for the education and training of power system operation and control for the power engineering study at university or for the training of the beginner at power industry.

• Journal of Biomedical Engineering Research
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• v.24 no.1
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• pp.45-53
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• 2003

Based on the 4-compartmental pharmacokinetic model developed in PART1, target-controlled infusion(TCI) pump system was designed and evaluated. The TCI system consists of digital board including microcontroller and digital signal process(DSP), analog board, motor-driven actuator, user friendly interface, power management and controller. It provides two modes according to the drugs: plasma target concentration and effect target concentration. Anaesthetist controls the depth of anaesthesia for patients by adjusting the required concentration to maintain both plasma and effect site in drug concentration. The data estimated in DSP include infusion rate, initial load dose, and rotation number of motor encoder. During TCI operation, plasma concentration. effect site concentration, awaken concentration, context-sensitive decrement time and system error information are displayed in real time. Li-ion battery guarantees above 2 hours without power line failure. For high reliability of the system, two microprocessors were used to perform independent functions for both pharmacokinetic algorithm and motor control strategy.

• 전기의세계
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• v.30 no.6
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• pp.375-385
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• 1981

New algorithms are derived for nonlinear programming problems which are characterized by their large variables and equality and inequality constraints. The algorithms are based upon the introduction of the Dependent-Variable-Elimination method, Independent-Variable-Reduction method, Optimally-Ordered-Triangular-Factorization method, Equality-Inequality-Sequential-Satisfaction method, etc. For a case study problem relating to the optimal determination of load flow in a 10-bus, 13-line sample power system, several approaches are undertaken, such as SUMT, Lagrange's Multiplier method, sequential applications of linear and quadratic programming method. For applying the linear programming method, the conventional simplex algorithm is modified to the large-system-oriented one by the introduction of the Two-Phase method and Variable-Upper-Bounding method, thus resulting in remarkable savings in memory requirements and computing time. The case study shows the validity and effectivity of the algorithms presented herein.

• Journal of Drive and Control
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• v.14 no.3
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• pp.1-7
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• 2017

Energy consumption of conventional hydraulic excavators controlled by MCV is considerable when negative load is applied because the meter orifice and meter-out orifice are machined in one spool. Therefore, IMV is introduced to save energy use of hydraulic excavators, but existing hydraulic excavators have various advantages so it is difficult to make a clear comparison. In this study, we compare the use of an existing MCV excavator that has many advantages such as negative control, and IMV for boom up and down operation, and if IMV is used to save energy, we will examine the cause. If possible, for comparability under the same conditions, both systems use pressure balance valves to minimize power consumption when not using power in the actuator. The orifice area at each notch of each valve is calculated, and energy saving is verified by comparing the two systems through simulation.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.1
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• pp.57-63
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• 2012

In this paper, a switch sizing method is proposed in order to prevent the cross-regulation in the TM type SIDO DC-DC buck converter. In TM type SIDO DC-DC buck converter, a DCM operation is required. In the DCM operation, the inductor peak current is larger than that in the CCM. Because of the larger inductor peak current and the added switch resistance, the voltage drop is increased, resulting in possible cross-regulation. To solve this problem, the switch resistance must be considered in sizing the switch. To simplify the calculation of the resistance, the inductor current was replaced by the average load current. Using the proposed method, TM type SIDO DC-DC buck converter for camera module was designed to provide two independent supply voltage(2.8 V and 1.8 V). The designed circuit was fabricated in a standard $0.35{\mu}m$ CMOS process. At a switching frequency of 1 MHz and a load current of 200 mA, a power effciency of 80.7% was achieved.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.3
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• pp.29-34
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• 2003

This paper describes the effects of sewage amount, temperature, and years in operation on the infiltration rate of a sewage disposal system. The self-purifying sewage disposal system, which is typically used in rural areas, consists of reeds and fine gravel. Water plants are planted on the gravel bed which provides the habitat for microbes. The basic process is that the gravel bed filters incoming sewage. Thus this system requires the smooth flow of sewage through the gravel. However, the efficiency of the disposal system will be lowered if the gravel bed is clogged with sewage sludge. A three year study shows that infiltration rate slows down significantly until the 7th day, depending on the sewage amount and the temperature. After the 7th day, the infiltration rate remains almost constant. In addition, the infiltration rate decreases as the temperature falls. It also decreases as the number of years in operation increase. But there is no significant change in the infiltration rate after the 7th day, independent of the temperature, the sewage amount, and years in operation. In order to take advantage of high infiltration rate, which improves the efficiency of the disposal system in its early stages, having two gravel beds and using them alternatively will be efficient. This operation method is called intermittent load and makes the disposal system last longer. The water plant roots above the gravel bed make the effective filtration possible because they delay accumulation of the sewage sludge and stabilize the filtration ability.