• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.301-307
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• 2009

In the paralleled converter module with peak current mode control, current imbalance appears when the voltage controllers with integral control of converter module are not exactly identical. In this paper, the voltage controller is designed to equal the current command of each converter module using the current command bus. The current balance controller is also proposed to balance the average currents of converter modules with imbalaced inductance. It is designed to have good transient response. Proposed method is implemented with the paralleled 2-module and 4-module boost converters with imbalanced inductance. Experimental results verify the performance of current share during both steady and transient states of converter.

• The Journal of Korean Physical Therapy
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• v.26 no.3
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• pp.175-181
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• 2014

Purpose: The purpose of this study is to investigate the effects of interference current therapy and laser therapy on functional recovery after total knee arthroplasty by measuring the Berg balance scale and range of motion. Methods: Subjects were 30 patients who were admitted to G Hospital after total knee arthroplasty. They were randomly assigned to experimental group I in which interference current therapy was applied (n=10), experimental group II in which laser therapy was applied (n=10), or the control group (n=10). The Berg balance scale and range of motion of the subjects were measured before, after 2 weeks, and after 4 weeks of therapy. Results: There was a statistically significant change (p<0.05) in the Berg balance scale and range of motion before and after therapy intervention among the laser therapy group and the interference current therapy group. There was also a significant change between the groups in the Berg balance scale and range of motion. Tukey's post hoc comparison showed a statistically significant difference between the control group and experimental group I and between the control group and experimental group II (p<0.05). Conclusion: The application of interference current therapy and laser therapy resulted in a significant change in both the Berg balance scale and range of motion among patients with total knee arthroplasty. The findings of this study can be used as preliminary clinical data in evaluating functional recovery in patients with total knee arthroplasty in a post-clinic setting.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1091-1093
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• 2001

The power semiconductor is widely used in the power plant or industrial field because of genealization and enlargement. It has been controlled and operated according to its own control method. Especially in case of Power plant, it plays a major role in AVR(Automatic Voltage Regulator) or electro chlorination control circuits. Generally, they used in Analog control system at above field. But each SCR current value is different because of load unbalance or switching characteristic variations, it may cause power plant unit trip or system disorder according to SCR element burn out or bad operating condition. Therefore, in this paper a development of 3 phase current balance control algorithm is described. it gets over the past analog control system limit, controls SCR gate firing angle for 3 phase current balance.

• Journal of The Korean Society of Integrative Medicine
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• v.3 no.2
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• pp.9-16
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• 2015

Purpose: The purpose of this research was to ascertain the effect of Micro-current on a pain, balance, of knee joint in the patients with degenerative arthritis. Method: The 30 subjects who had micro-current in this research and randomly assigned into two group, an experiment group and a control group. micro-current was applied to 15 subject in the experiment group after general physical therapy. experiment group was applies general therapies and micro-current stimulation. The measurement were analyzed by using SPSS(V.20). In order to compare the post to the amount of pre-changes and post-changes of each group, the paired t-test was used. The difference between the experiment group and the control group was analyzed by using the analysis of convariance. Results: The results of this study were as follows; 1) In VAS measures, the pain point was significantly decreased in both the experimental and the control group. 2) Mc Gill Pain Questionnaire(MPQ), the pain point was significantly decreased in both the experimental and the control group. 3) TUG measures, the second was significantly decreased in both the experimental and the control group. 4) Weight distribution measures, the authority was significantly decreased in both the experimental and the control group. Conclusion: The micro-current is considered a degenerative knee arthritis that can be presented as an effective physical therapy intervention.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.90-94
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• 1998

The parallel inverter is popularly used because of its fault-tolerance capability, high-current outputs at constant voltages and system modularity. The conventional parallel inverter usually employes active and reactive power control or frequency and voltage droop control. However, these approaches have the disadvantages that the response time of parallel inverter control is slow against load and system parameter variation to calculate active, reactive power, frequency and voltage. This paper describes a novel control scheme for power equalization in parallel connected inverter. The proposed scheme has a fast power balance control response, a simplicity of implementation, and inherent peak current limiting capability since it employes a instantaneous current/voltage control with output voltage and current balance and output voltage regulation. A design procedure for the proposed parallel inverter controller is presented. Futhermore, the proposed control scheme is verified through the simulation in various cases such as the system parameter variation, the control parameter variation and the nonlinear load condition.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1659-1669
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• 2018

An improved circulating current suppression control method is proposed in this paper. In the proposed controller, an outer loop of the average capacitor voltage control model is used to balance the sub-module capacitor voltage. Meanwhile, an individual voltage balance controller and an arm voltage balance controller are also used. The DC and harmonic components of the circulating current are separated using a low pass filter. Therefore, a multiple quasi-proportional-resonant (multi-quasi-PR) controller is introduced in the inner loop to eliminate the circulating harmonic current, which mainly contains second-order harmonic but also contains other high-order harmonics. In addition, the parameters of the multi-quasi-PR controller are designed in the discrete domain and an analysis of the stability characteristic is given in this paper. In addition, a simulation model of a three-phase MMC system is built in order to confirm the correctness and superiority of the proposed controller. Finally, experiment results are presented and compared. These results illustrate that the improved control method has good performance in suppressing circulating harmonic current and in balancing the capacitor voltage.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.176-181
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• 1998

The parallel inverter is popularly used because of its fault-tolerance capability, high-current outputs at constant voltages and system modularity. The conventional parallel inverter usually employs active and reactive power control of frequency and voltage droop control. However, these approaches have the disadvantages that the response time of parallel inverter control is slow against load and system parameter variation to calculate active, reactive power, frequency and voltage. This paper describes a novel control scheme for power equalization in parallel-connected inverter. The proposed scheme has a fast power balance control response, a simplicity of implementation, and inherent peak current limiting capability since it employees an instantaneous current/voltage control with output voltage and current balance and output voltage regulation. A design procedure for the proposed parallel inverter controller is presented. Furthermore, the proposed control scheme is verified through the experiment in various cases such as the system parameter variation, the control parameter variation and the nonlinear load condition.

• Journal of The Korean Society of Integrative Medicine
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• v.11 no.2
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• pp.101-108
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• 2023

Purpose : To investigate effects of transcranial directed current stimulus (tDCS) combined with abdominal draw-in maneuver (ADIM) on balance ability and trunk impairment scale of chronic stroke patients. Methods : Twenty-six chronic stroke patients were recruited and twenty-four participated after excluding two patients who met the exclusion criteria. After screening tests, they were randomized through excel program into an experimental group (n = 12) to apply a tDCS combined with ADIM and a control group (n = 12) to apply a sham tDCS with ADIM. The intervention lasted three times a week for six weeks. To compare tDCS intervention effects, trunk impairment scale and balance ability were measured. Comparisons between experimental and control groups were statistically processed using an independent t-test and comparisons within groups were statistically processed using a paired t-test. Results : The experimental group showed significant increases of pre- and post-intervention medial lateral velocity, anterior posterior velocity and area of balance ability, and trunk impairment scale (p<.05). The control group showed significant increases in pre- and post-intervention medial lateral velocity of balance ability and trunk impairment scale (p< .05). The experimental group showed significant increases of medial lateral velocity of balance ability and trunk impairment scale compared to the control group (p<.05). Conclusion : Results of this study suggest that tDCS combined with ADIM for chronic stroke patients can be effective in improving medial lateral velocity of balance ability and trunk impairment scale. Thus, tDCS can be used as an effective treatment protocol for trunk rehabilitation of chronic stroke patients.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1088-1090
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• 2001

In general, Power SCR(Silicon Controlled Rectifier) is most widely used in Power Plant as well as Industrial field. It has been controlled and operated according to its own control method. Especially, in case of Power plant, it plays a major role in AVR(Automatic Voltage Regulator) or electro chlorination control circuits. Generally, they used in Analog control system at above field. But each SCR current value is different because of load unbalance or switching characteristic variations, it may cause power plant unit trip or system disorder according to SCR element burn out or bad operating condition. Therefore, in this paper a development of 3 phase current balance control unit is described, it gets over the past analog control system limit, uses DSP(Digital signal processor) had high speed response, controls SCR gate firing angle for 3 phase current balance.

• Journal of Power Electronics
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• v.19 no.2
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• pp.487-496
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• 2019

For a solid-state transformer (SST), some factors, such as signal delay, switching loss and differences in the system parameters, lead to unbalanced DC-link voltages among the cascaded H-bridges (CHB). With a control method implemented in the ${\alpha}{\beta}$ frame, the DC-link voltages are balanced, and the reactive power is equally distributed among all of the H-bridges. Based on the ${\alpha}{\beta}$ frame control, the system can achieve independent active current and reactive current control. In addition, the control method of the high-voltage stage is easy to implement without decoupling or a phase-locked loop. Furthermore, the method can eliminate additional current delays during transients and get the dynamic response rapidly without an imaginary current component. In order to carry out the controller design, the vector refactoring relations that are used to balance DC-link voltages are derived. Different strategies are discussed and simulated under the unbalanced load condition. Finally, a three-cell CHB rectifier is constructed to conduct further research, and the steady and transient experimental results verify the effectiveness and correctness of the proposed method.