• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.5
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• pp.921-928
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• 2011

This paper presents a new method of local voltage control to achieve coordinative control among UPFC(Unified Power Flow Controller) and conventional reactive compensation equipments, such as switched-shunt and ULTC(Under-Load Tap Changing) transformer. Reactive power control has various difficult aspects to control because of difficulty of system analysis. Recently, the progress of power electronics technologies has lead to commercial availability of several FACTS(Flexible AC Transmission System) devices. The UPFC(Unified Power Flow Controller) simultaneously allows the independent control of active and reactive power flows as well as control of the voltage profile. When conventional reactive power sources and UPFC are used to control system voltage, the UPFC reacts to the voltage deviation faster than the conventional reactive power sources. Keeping reactive power reserve in an UPFC during steady-state operation is always needed to provide reactive power requirements during emergencies. Therefore, coordination control among UPFC and conventional reactive power sources is needed. This paper describe the method to keep or control the voltage of power system of local area and to manege reactive power reserve using PSS/E with Python. The result of simulation shows that the proposed method can control the local bus voltage within the given voltage limit and manege reactive power reserve.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1625-1636
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• 2017

A power electronic transformer (PET) based on the cascaded H-bridge (CHB) and the isolated bidirectional DC/DC converter (IBDC) is capable of accommodating a large scale battery energy storage system (BESS) in the medium-voltage grid, and is referred to as a power electronic transformer based battery energy storage system (PET-BESS). This paper investigates the PET-BESS and proposes a coordinative control strategy for it. In the proposed method, the CHB controls the power flow and the battery state-of-charge (SOC) balancing, while the IBDC maintains the dc-link voltages with feedforward implementation of the power reference and the switch status of the CHB. State-feedback and linear quadratic Riccati (LQR) methods have been adopted in the CHB to control the grid current, active power and reactive power. A hybrid PWM modulating method is utilized to achieve SOC balancing, where battery SOC sorting is involved. The feedforward path of the power reference and the CHB switch status substantially reduces the dc-link voltage fluctuations under dynamic power variations. The effectiveness of the proposed control has been verified both by simulation and experimental results. The performance of the PET-BESS under bidirectional power flow has been improved, and the battery SOC values have been adjusted to converge.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.700-704
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• 2011

This paper proposes a coordinative protection study results of 22.9kV HTS(High-Temperature Superconducting) cable implemented distribution system. HTS cable can provide about 5 times larger transfer capacability compare to conventional XLPE cable, however, it has different heat characteristic so called quench. This paper presents the simulation results on Ichun substation HTS cable which connects main transformer and 22.9kV bus. Various expected fault cases are considered and discussed to examine whether conventional protection scheme is effective to protect both of existing facilities and HTS cable. With the results of simulation, conventional protection scheme can be used if instantaneous element and time inverse elements could be adjusted with proper time coordination. Internal temperatures of HTS cable conductor in safe region with proper protection without quench. This results are to be demonstrated by the field test and will be implemented in Ichon substation HTS cable protection and control system.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.154-155
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• 2006

This study investigated a mechanism for controlling the shape of Cu nanocrystals fabricated using the polyol process, which considers the thermodynamic transition from a facetted surface to a rough surface and the growth mechanisms of nanocrystals with facetted or rough surfaces. The facetted surfaces were stable at relatively low temperatures due to the low entropy of perfectly facetted surfaces. Nanocrystals fabricated using a coordinative surfactant stabilized the facetted surface at a higher temperature than those fabricated using a non-coordinative surfactant. The growth rate of the surface under a given driving force was dependent on the surface structure, i.e., facetted or rough, and the growth of a facetted surface was a thermally activated process. Surface twins decreased the activation energy for growth of the facetted surface and resulted in rod- or wire-shaped nanocrystals

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.29 no.1
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• pp.69-79
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• 2023

Purpose: This study examined the possibility of muscle strength and balance ability improvement through coordinative locomotor training by making a difference on the supporting plane using a resistance band for adolescent athlete of Taekwondo sparring athletes. Methods: A total of 22 students were selected as to the participants of the study, and 11 students each were randomly assigned to the control and experimental group for coordination locomotor training using a resistance band on stable and unstable supporting surface. The training period was 60 min, three times a week, for 8 weeks in total. To confirm changes on balance ability of each participant, balance assessment devices are used. Moreover, surface electromyography was used for muscle strength evaluation. Results: After coordinated locomotor training using a resistance band for 8 weeks, the difference bet ween groups was not significant; Also, the improvement in strength was no significant difference in other muscles in the between groups, but there was a significant in the muscle activity of the rectus muscle of the right thigh in the experimental group. Conclusion: The participants demonstrated that coordinative locomotor training using the elastic band on an unstable supporting surface was able to obtain junctional effects for the prevention of exercise injuries in youth taekwondo sparring athletes, and muscle activity exercise of the rectus muscle of the right thigh was particularly effective.

• Journal of Korean Physical Therapy Science
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• v.30 no.3
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• pp.59-71
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• 2023

Background: This study was to investigate the effects of coordinative locomotor training(CLT) using elastic bands on pain, dynamic balance, muscle strength, and muscle activity of female college students with patellofemoral pain syndrome(PFPS). Design: Randomized Controlled Trial Methods: Twenty-six female college students with PFPS were assigned randomly to an experimental(n=13) or control(n=13) group. The experimental group performed CLT using an elastic band. The control group performed squat exercises to strengthen muscle strength. The 30-minute inter- vention was applied a total of twelve times, three times a week for four weeks. All subjects measured the pain, the muscle strength, the dynamic balance, and the muscle activity(VL/VM ratio) before and after intervention. A paired t-test was used for the determination of differences before and after treatment, and an independent t-test was used for the determination of differences between treatment groups. Results: As a result of comparison within groups, the experimental group showed significant differences in pain, muscle strength, dynamic balance, and VL/VM ratio after the experiment(p<0.05), and the control group showed significant differences in pain, muscle strength, and dynamic balance after the experiment(p<0.05). In comparison between the two groups, the experimental group showed more significant differences in pain, dynamic balance, and VL/VM ratio than the control group(p<0.05), and the control group showed more significant differences in muscle strength than the experimental group(p<0.05). Conclusion: Based on these results, CLT using elastic bands effectively improved the pain, muscle strength, dynamic balance, and VL/VM ratio of female college students with PFPS.

• Journal of Acupuncture Research
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• v.26 no.5
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• pp.137-149
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• 2009

Objectives : This study was designed to analyze whether General Coordinative Manipulation(GCM) Intervention could have effects on the balanced restoration of asymmetrical posture. Methods : Sixty eight(68) healthy volunteers(1st hypothesis: 46, 2nd hypothesis 22) participated in two GCM interventions, which have been performed 2 times a week for 3 weeks. The Global Postural System(GPS) Unit was used to measure the posture, and measurements were performed before and after the application of each intervention group. A paired t-test and wilcoxon test were used to determine the statistical significance. Results : The outcome of examining the hypothesis is as follows: 1. The 1st hypothesis: It has been proved that GCM Intervention, which coordinates the flexion type of upper extremity and the extension type of lower extremity, excluding self-care, shows the efficiency in treatment on more than two aspects of 3 parts: anterior, posterior and lateral postures, and the effects on more than 3 of 4 body types. 2. The 2nd hypothesis: It has been proved that GCM Intervention, which coordinates the flexion type of lower extremity and the extension type of upper extremity, excluding self-care, shows the treatment in efficiency on more than two aspects of 3 parts: anterior, posterior and lateral postures, and the effects on more than 2 of 3 body types. Conclusions : GCM intervention programs on the two hypothesis groups have an affect on the balanced restoration of the postural control system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2131-2134
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• 2010

In this paper, the on-line system schemes for coordinated control system of multiple FACTS were presented to enhance the voltage stability around the metropolitan areas. In order to coordinated control system of FACTS devices, MFC on-line system calculates the optimal set point(Vref, Qrev) of FACTS devices using the coordinated control algorithm with real time network data which is transferred from SCADA/EMS system. If the system is unstable after contingencies, the new operation set-point of FACTS would be determined using bus sensitivity from tangent vector at voltage instability point. Otherwise, we would determine the new operation set-point of FACTS for considering economical operation, like as active power loss minimization using Optimal Power Flow algorithm. As the test, MFC(Multiple FACTS Coordinated control) on-line system will be installed in Korea power system.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.181-183
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• 2008

This paper suggests local voltage control method to achieve coordinative control between STATCOM and other reactive power resources, such as Shunt Capacitor/Reactors and OLTC. Voltage/Reactive power control has various difficult aspects to control because of analysis and system dynamics error. This control method suggests practical algorithm regarding system voltage and reactive power status which is easy to implement in substation basis. In normal status, STATCOM-Shunts-OOTC are in operation. In emergency status, OLTC is locked. This algorithm is tested and verified in EMTDC.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.1-7
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• 1998

Robots utilized in the field of welfare or agriculture should be light in weight and flexible in structure. A pneumatic actuator has properties such that it is more powerful compared with a motor of same weight, and that it is flexible, clean and unexplosive. In this paper we propose a new structure of the pneumatic actuator with two-degree-of-freedom. By using proposed pneumatic actuators, we can easily construct multi-degree-of-freedom pneumatic manipulators. Here we constructed a fourteen-degree-of-freedom pneumatic dual manipulator. The performance of the dual manipulators is confirmed through experiments for ball-handling with impedance control. In the experiments several control schemes, including the decentralized control and the simple adaptive control (SAC), were used. The results show that a flexibility of the pneumatic actuator is appropriate to accomplish the coordinative motion of the right and left arms of the robot.