• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.504-507
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• 1997

It is well known that Variable Structure Controller(VSC) is robust to parameters variation and disturbance but its performance depends on the design parameters such as switching gain and slope of sliding surface. This paper proposes a more robust VSC that is composed of local VSC's. Each local VSC considers the local system dynamics with narrow parameter variation and disturbance. First we optimize the local VSC's by use of Evolution Strategy, and next we use Artificial Neural Network to generalize the local VSC's and construct the overall VSC in order to cover the whole range of parameter variation and disturbance. Simulation on BLDC motor current control shows that the proposed VSC is superior to the conventional VSC.

• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.452-455
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• 1997

It is well known that Variable Structure Controller(VSC) is robust to parameters variation and disturbance but its performance depends on the design parameters such as switching gain and slope of sliding surface. This paper proposes a more robust VSC that is composed of local VSC's. Each local VSC considers the local system dynamics which has narrow parameter variation and disturbance. We optimize the local VSC's by use of Evolution Strategy, and then we use Artificial Neural Network to generalize the local VSC's and construct the overall VSC in order to cover the whole range of parameter variation and disturbance. Simulation on BLDC motor current control has verified the proposed VSC is superior to the conventional VSC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1178-1183
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• 2008

The variable structure control(VSC) with sliding mode is an important and interesting topic in modern control of nonlinear systems. However, the discontinuous control law in VSC leads to undesirable chattering in practice. As a method solving this problem, in this paper, we propose a scheme of the VSC with neural network sliding surface. A neural network sliding surface with boundary layer is employed to solve discontinuous control law. The proposed controller can eliminate the chattering problem of the conventional VSC. The effectiveness of the proposed control scheme is verified by simulation results.

• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.544-551
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• 2020

Reactor control is a standout amongst the most vital issues in the nuclear power plant. In this paper, the optimal design of variable structure controller (VSC) based on the lightning search algorithm (LSA) is proposed for a nuclear reactor power system. The LSA is a new optimization algorithm. It is used to find the optimal parameters of the VSC instead of the trial and error method or experts of the designer. The proposed algorithm is used for the tuning of the feedback gains and the sliding equation gains of the VSC to prove a good performance. Furthermore, the parameters of the VSC are tuned by the genetic algorithm (GA). Simulation tests are carried out to verify the performance and robustness of the proposed LSA-based VSC compared with GA-based VSC. The results prove the high performance and the superiority of VSC based on LSA compared with VSC based on GA.

• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.4
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• pp.7-13
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• 2005

This paper presents modeling and ostimator/controller design for the hydraulic system in Vehicle Stability Control(VSC) system. A nonlinear mathematical model of the VSC hydraulic system is proposed and its accuracy is experimentally verified. A brake pressure estimator is then designed based on the derived mathematical model of VSC hydraulic system. And a disturbance observer, which compensates the estimation error between the brake pressure and the computed brake pressure is also designed to enhance the accuracy of the estimator. The proposed controller has the form of a feedback controller and determines explicitly the on/off ratio of valves' driving PWM signals by means of making use of the simplified mathematical model in the VSC hydraulic system. The performance of the designed controller whose feedback signal is generated by the brake pressure estimator is validated through experimental results.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.263-269
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• 2018

In this study, a selective inverter operation between a 2-level voltage source converter (VSC) and a 3-level T-type VSC (3LT VSC) is proposed to improve the efficiency of a 3LT VSC. The 3LT VSC topology, except for its neutral-point switches, has similar operations as that of the 2-level VSC. If an operation mode is changed according to efficiency, the efficiency can be improved because efficiencies of each methods are depending on current and MI (Modulation Index). The proposed method calculates the power losses of the two topologies and operates as the having lower losses. To calculate the losses, the switching and conduction losses based on the operation mode of each topology were analyzed. The controller determined the operation mode of the 2- or 3-level VSC based on the power loss calculated during every cycle. The validity of the proposed control scheme was investigated through simulation and experiments. The waveform and average efficiency of each method were compared.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.1
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• pp.65-71
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• 2020

Recently, interest in the DC transmission is rapidly increasing worldwide. In many countries and leading companies are prior to the aggressive development of HVDC technology and application. Especially, VSC-HVDC system has been widely applied to transfer power at long distance between power plant and power consumption area. Therefore in this paper, we analyzed the benefit-cost of VSC-HVDC system which has more advantages than existing transmission system. The proposed system is MMC(Modular Multilevel Converter) VSC-HVDC system that have stability of Power Grid, interconnect Large-scale New Power Generation Plants by prevents Blackout. And MMC VSC-HVDC system Reduced the loss importing foreign systems. And the benefits were calculated in four stages, and the costs were applied to the actual project. By evaluating the various avoidance costs compared to the benefit-cost, it was confirmed that MMC VSC-HVDC system was advantageous in system stability and economic and social benefits.

• Journal of Periodontal and Implant Science
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• v.34 no.2
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• pp.449-459
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• 2004

Bacterial byproducts and volatile sulfur compounds(VSC) have been found to be the leading intra-oral agents, specifically, the byproducts of gram negative anaerobic bacteria have been implicated as primary factors of halitosis in patients presenting with periodontal disease. The objective of this study was to determine the correlation between periodontal treatment and the subsequent reduction in the level of halitosis. Forty-three subjects presenting with periodontal disease were examined before periodontal treatment, one week after treatment, one month after treatment, and finally, two months after treatment, using a portable sulfide monitoring $Halimeter^{(R)}$ to measure the VSC concentrations at the prescribed intervals. The results of the study were as follows: 1. Significant decreases in the mean VSC concentration were observed at the one week, one month, and two month post-op intervals relative to the pre-op measurement. (p<0.05) 2. Significant decreases in the mean VSC concentration were observed in subjects after completion of flap operations. Significant decreases in the mean VSC concentration were observed at the one and two month post-flap operation measurement relative to the VSC concentration at one week (p<0.05), but no significant differences between the one month and two month VSC concentrations were found. (p<0.05) 3. Significant decreases in the mean VSC concentration were observed in subjects after completion of subgingival curettage (p<0,05). Significant decreases were found between the one week and one month measurements and between the one month and two month measurements, but significant differences were not observed between the one week and two month measurements. (p<0.05) The results of this study show significant decreases in VSC concentration in test subjects after periodontal treatment. It can be inferred from the results above, that periodontal disease is a significant contributing factor of halitosis, and that treatment of periodontal disease can been an effective means of reducing VSC concentration in patients presenting with halitosis concurrent with periodontal disease.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2196-2201
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• 2011

According to the 5th national plan for electric power demand and supply, the 3rd HVDC link will be installed between KEPCO and Jeju Island system and go into operation in June, 2016. However, if it adopt LCC HVDC, Jeju power system could be in voltage instable condition. In order to solve the problem, we propose the application of VSC HVDC to the 3rd HVDC project. In the past, VSC HVDC has many disadvantages such as, inefficiency in conversion, size limit, and expensiveness, compared to LCC HVDC. Recently, the new technologies and the demand for renewable energy interconnection are leading a large growth in VSC HVDC market. In this paper, we will introduce the technical and market trends of VSC HVDC and power system stability analysis results for Jeju power system having LCC and VSC HVDCs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.343-348
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• 2014

Recently, applications of VSC-HVDC systems to power systems are growing because of their control ability of reactive power. Meanwhile, the hardware-in-the-loop simulation (HILS) based on the real-time digital simulator has been applying to develop and test imbedded controllers and systems in the power industry to decrease costs and to save time. In this paper, a 3-level neutral point clamped (NPC) VSC-HVDC system is modeled and the embedded controllers of the NPC VSC-HVDC system are designed. The designed controllers are implemented by TMS320F28335. The TMS320F28335-based controllers of the NPC VSC-HVDC system are tested using the HILS.