• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.5
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• pp.328-335
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• 2018

An energy management method of DC microgrids using voltage compensation term is proposed in this study. Droop control is often implemented to operate the DC microgrid. However, the droop control necessarily generates voltage variation. Energy flow is also difficult to control because the droop control mainly focuses on proportional load sharing. To solve these problems, the voltage compensation term based on the low-bandwidth communication is used to determine the operating band of the converter. Energy management and voltage variation minimization can be achieved by judging the operating band according to the magnitude of voltage compensation term. The validity of the proposed method is verified by simulation and experiments.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.2
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• pp.183-187
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• 2011

As larger the commercial vessel is, and rougher the marine environment becomes nowadays, drag embedment type anchor (DEA) of more stable performance and higher holding power is requested to be applied on the vessel. But, the performance of DEA has not become well known to academy and industries so far, that the basic study of DEA performance and holding force for the development of new DEA of higher performance is insufficient that required. In this paper, three types of same holding category DEA model (HALL, AC-14, POOL-N, scale 1/10), which are generally applied on the commercial vessel nowadays, were tested by being horizontally dragged on the test tank, on which sand was being floored with sufficient depth, and measured the holding force of each anchor simultaneously using load cell and D/A converter. With the test results, the embedding motion was analyzed to have three different stages and the holding force of each anchor was analyzed with respect to the anchor geometry, such as shape and weight of each type of anchors, and final embedding depth.

• Journal of electromagnetic engineering and science
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• v.11 no.3
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• pp.143-151
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• 2011

This paper presents a survey of recent wireless power transfer systems. The issue of wireless power transfer is to achieve a highly efficient system with small positioning errors of the facilities setting. Several theories have been presented to obtain precise system design. This paper presents a summary of design theory for short range power transfer systems and detailed formulations based on a circuit model and an array of infinitesimal dipoles. In addition to these theories, this paper introduces a coil array scheme for improving the efficiency for off axis coils. In the microwave range, tightly coupled resonators provide a highly efficient power transfer system. This paper present san-overlay resonator array consisting of half wavelength microstrip line resonators on the substrate with electromagnetically coupled parasitic elements placed above the bottom resonators. The tight couplings between the waveguide and the load resonator give strong power transmission and achieve a highly efficient system, and enables a contact-less power transfer railroad. Its basic theory and a demonstration of a toy vehicle operating with this system are presented. In the last topic of this paper, harmonic suppression from the rectenna is discussed with respect to acircular microstrip antenna with slits and stubs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.7
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• pp.1553-1557
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• 2004

A real-time processing system for embedded hardware genetic algorithm is suggested. In order to operate basic module of genetic algorithm in parallel, such as selection, crossover, mutation and evaluation, dual processors based architecture is implemented. The system consists of two Xscale processors and two FPGA with evolvable hardware, which enables to process genetic algorithm efficiently by distributing the computational load of hardware genetic algorithm to each processors equally. The hardware genetic algorithm runs on Linux OS and the resulted chromosome is executed on evolvable hardware in FPGA. Furthermore, the suggested architecture can be extended easily for a couple of connected processors in serial, making it accelerate to compute a real-time hardware genetic algorithm. To investigate the effect of proposed approach, performance comparisons is experimented for an typical computation of genetic algorithm.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.5
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• pp.366-372
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• 2018

Three-port dual-active bridge (DAB) converter in a DC microgrid was studied due to its high power density and cost-effectiveness. The other advantages of DAB include galvanic isolation and bidirectional power conversion capability using simple control modulation. The three-port DAB converter consists of a three winding transformer and three bridges. The transformer has three phases, which means that the ports are coupled. Thus, the three-port DAB converter causes unwanted power flows when the load connected to each port changes. The basic operational principles of the three-port DAB converter are presented in this study. The decoupling control strategy of the independent port power transfer is presented with a mathematical power model to overcome the unexpected power flow problem. The validity of the proposed analysis and control strategy is verified with PSIM simulation and experiments using a 1-kW prototype power converter.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.7
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• pp.317-326
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• 2002

In this paper, a methodology for optimal PI supplementary controller using the modified genetic algorithm has been proposed to the oscillation damping in HDVC transmission system. These study processes are summarized as the formulation for load flow calculation in HVDC transmission system with SVC, the investigations on the basic control in HVDC system, the mathematical modeling for dynamic characteristics analyses, and the optimal design of MGA based PI controller generation the supplementary control signal of SVC. Its properties were verified through a series of computer simulations including dynamic stability. It means that the application of MGA-PI controller in HVDC transmission system can contribute the propriety to the improvement of the stability in HVDC transmission system and the design of MGA-OI controller has been proved indispensible when applied to HVDC transmission system.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.5
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• pp.257-263
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• 2000

One of the basic assumptions in the static gait design for a walking robot is that the weight of leg should be negligible compared to that of body, so that the total gravity center is not affected by swing of a leg. Based on the ideal assumption of zero leg-weight, conventional static gait has been simply designed for the gravity center of body to be inside the support polygon, consisting of each support leg's tip position. In case that the weight of leg is relatively heavy, however, while the gravity center of body is kept inside the support polygon, the total gravity center of walking robot can be out of the polygon due to weight of a swinging leg, which causes instability in walking. Thus, it is necessary in the static gait design of a real robot a compensation scheme for the fluctuation in the gravity center. In this paper, a body impedance control is proposed to obtain the total gravity center based on foot forces measured from load cells of a real walking robot and to adjust its position to track the pre-designed trajectory of the corresponding ideal robot's body center. Therefore, the walking stability is secured even in case that the weight of leg has serious influence on the total gravity center of robot.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.459-464
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• 2008

While high speed / precision investigating for maximization of Textile Machinery business is requesting a machine which has highly endurance, stability and reliance abilities following customer request. In this research, load volume that gives influence on loom is measured and analyzed for water jet loom in real operation time to driving system adhered torque sensor to each a module. As well, measurement and analysis technology are developed about torque and vibration of driving systems for textile machinery by comparing dynamical analysis of water jet loom with gained result, basic materials about development of high value added textile machinery which has endurance and stability are presented.

• Korean Journal of Rural Living Science
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• v.9 no.2
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• pp.43-50
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• 1998

To obtain basic data for efficient health plan, we investigated the condition of farmers' health, living behavior, working environment, and cumulative fatigue symptoms by crops (greenhouse melon, rice and red pepper, stock farming, pear, grapes, dropwort, sweet potato, potato, radish. cabbage). The results are as follows; (1) The condition of farmers health : Among them, cabbage cultivators were in bad health concerning cardiovascular system, musculo-skeletal system, and skin condition. (2) Living behavior : $\circled1$ Radish cultivators were in best of their physical condition. $\circled2$ Rice and red pepper cultivators were taking a regular recess as compared with dropwort cultivators. $\circled3$ On concerning bathe, sleeping, and clothes, stock farmers were in relatively bad condition. (3) Working environment : cabbage, greenhouse melon, and dropwort cultivators had relatively Poor working environment. (4) Cumulative fatigue symptoms : $\circled1$ Dropwort cultivators were in the worst of their condition concerning loss of their energy, physical condition. decline of will to labor, sense of unease, and low spirits. $\circled2$ On concerning general fatigue, dropwort, sweet potato, and cabbage cultivator were in bad condition.

• Structural Engineering and Mechanics
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• v.62 no.4
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• pp.443-453
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• 2017

The performance of bolted side-plated (BSP) beams is affected by the degree of transverse partial interaction, which is a result of the interfacial slip caused by transverse shear transfer between the bolted steel plates and the reinforced concrete beams. However, explicit formulae for the transverse shear transfer profile have yet to be derived. In this paper, a simplified piecewise linear shear transfer model was proposed based on force superposition principle and simplification of shear transfer profiles derived from a previous numerical study. The magnitude of shear transfer was determined by force equilibrium and displacement compatibility condition. A set of design formulae for BSP beams under several basic load cases was also derived. Then the model was verified by test results. A worked example was also provided to illustrate the application of the proposed design formulae. This paper sheds some light on the shear force transfer mechanism of anchor bolts in BSP beams, and offers a practical method to evaluate the influence of transverse partial interaction in strengthening design.