• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.361-366
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• 2013

This paper presents the effect on application of the flywheel energy storage system (FESS) for load frequency control (LFC) of an interconnected 2 area power system. To do this, the control characteristics with the FESS were compared with that of the conventional governor controller. The controller for the FESS control and the governor control used a PID type controller. Both the FESS PID controller and the governor PID controller using genetic algorithm (GA) were designed to optimize the PID parameters. The frequency and generation output characteristics with the only FESS controller and with the only conventional governor controller were compared. To verify robust performance of the FESS controller, the computer simulations were performed under various disturbances. The simulation results showed that the FESS controller provided better dynamic responses in comparison with the conventional governor controller.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.354-355
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• 2018

Flywheel energy storage system (FESS) operates motor or generator by utilizing the stored kinetic energy in the rotating mass. Thus, the FESS can support the frequency control of the power system. However, the FESS is disabled when the rotor speed reaches to its minium value. Thus, the second frequency dip occurs in the power system. This paper proposes the frequency control scheme of FESS based on a variable gain depending on the rotor speed and frequency deviation. The proposed scheme prevents the second frequency dip because the variable gain decreases depending on the stored in the FESS. The performance of the proposed scheme is investigated for the IEEE 14-bus system.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.10
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• pp.99-106
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• 2008

5kWh FESS(Flywheel Energy Storage System) using AMB(Active Magnetic Bearing) has been under development and 1st trial system has been finished and run the operating test. Unfortunately, the test result was not satisfactory because FESS could increase the rotational speed up to 9,000 rpm only although the target rotational speed is 18,000rpm. It's because 1st bending mode frequency of flywheel shaft was too low and imbalance response was too big. To achieve the target speed, 1st bending mode and imbalance response must be improved and the whole FESS needed to be designed again. This paper presents the newly designed FESS and what has been changed from the 1st trial FESS to improve 1st bending mode and imbalance response. The experimental results to see how much 1st bending mode frequency was improved are presented, too.

• Imaging Science in Dentistry
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• v.50 no.4
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• pp.299-307
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• 2020

Purpose: The diagnosis of chronic rhinosinusitis requires a comprehensive knowledge of the signs and symptoms of the disease and an accurate radiographic assessment. Computed tomography (CT) is the superior imaging modality for diagnosis of chronic rhinosinusitis. However, considering the lower dose and higher resolution of cone-beam computed tomography (CBCT) compared to CT, this study aimed to assess the agreement between the findings of CBCT and functional endoscopic sinus surgery (FESS). Materials and Methods: This descriptive prospective study evaluated 49 patients with treatment-resistant chronic rhinosinusitis who were candidates for FESS. Preoperative CBCT scans were obtained before patients underwent FESS. The agreement between the CBCT findings and those of FESS was determined using the kappa correlation coefficient. The frequency of anatomical variations of the paranasal sinuses was also evaluated on CBCT scans. Results: Significant agreement existed between pathological findings on CBCT scans and those of FESS, such that the kappa correlation coefficient was 1 for mucosal thickening, 0.644 for nasal deviation, 0.750 for concha bullosa, 0.918 for nasal polyp, 0.935 for ostiomeatal complex (OMC) obstruction, and 0.552 for infundibulum thickening. Furthermore, 95.9% of patients had 1 or more and 79.6% had 2 or more anatomical variations, of which nasal deviation was the most common (67.3%). Conclusion: Considering the significant agreement between the findings of CBCT and FESS for the detection of pathological changes in the paranasal sinuses, CBCT can be used prior to FESS to detect chronic rhinosinusitis and to assess anatomical variations of the OMC.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.229-234
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• 2014

In this paper, a design problem of the flywheel energy storage system controller using genetic algorithm (GA) is investigated for a frequency control of the wind diesel hybrid power generation system in an isolated power system. In order to select parameters of the FESS controller, two performance indexes are used. We evaluated a frequency control effect for the wind diesel hybrid power system according to change of the weighted values of a performance index. To verify performance of the FESS controller according to the weighted value of the performance index, the frequency domain analysis using a singular value bode diagram and the dynamic simulations for various weighted values of performance index were performed. To verify control performance of the designed FESS controller, the eigenvalue analysis and the dynamic simulations were performed. The control characteristics with the two designed FESS controller were compared with that of the conventional pitch controller. The simulation results showed that the FESS controller provided better dynamic responses in comparison with the conventional controller.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.256-261
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• 2017

This paper deals with the experimental evaluation on power loss of a double-side permanent magnet synchronous motor/generator (DPMSM/G) applied to a flywheel energy storage system (FESS). Power loss is one of the most important problems in the FESS, which supplies the electrical energy from the mechanical rotation energy, because the power loss decreases the efficiency of energy storage and conversion of capability FESS. In this paper, the power losses of coreless DPMSM/G are separated by the mechanical and rotor eddy current losses in each operating mode. Moreover, the rotor eddy current loss is calculated by the 3-D finite element analysis (FEA) method. The analysis result is validated by separating the power loss as electromagnetic loss and mechanical loss by a spin up/down test.

• Journal of the Korean Magnetics Society
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• v.27 no.1
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• pp.1-8
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• 2017

Flywheel Energy Storage System (FESS) is composed by flywheel generating rotating potential energy and motor/generator set charging and discharging electric potential energy. The flywheel and motor/generator is connected by rotating shaft. And torque characteristics of motor/generator part can influence charging and mechanical traits of FESS. This paper analyze about motor/generator design method of 5 [kWh] FESS and torque ripple, harmonic effects by change of slots. At First, this paper proposes a method to estimate the flywheel size and the rotor size of the motor from the the rotational kinetic energy by inertia of FESS. The number of induction motor rotor slots for torque ripple reduction in the high speed operation region is selected. This paper performs to reduce the noise and vibration of the flywheel composed of coaxial with motor/generator and flywheel and realize the high efficiency.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.2
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• pp.170-177
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• 1998

The purpose of superconducting magnetic bearing flywheel energy storage system(SMB-FESS) is to store unused nighttime electricity as kinetic energy and convert it to electricity during daytime. The SMB-FESS is proposed as an efficient energy storage system because there is no mechanical problems, such as friction and wear The flywheel over SMB is rotated at a high speed, 50,000rpm. The major source of energy loss in the SMB-FESS is vibration of flywheel. Therefore, the vibration characteristics of SMB-FESS should be identified. In this study, the axial/radial stiffness and damping coefficient of SMB are measured by a vibration test. Natural frequencies and natural modes of flywheel and magnet are analyzed by a finite element method. The modal analysis of system is performed using the modal parameters of each component and the measured stiffness/damping coefficient. So, natural at frequencies and mode shapes of the joined system can be obtained. According to critical speed analysis, the system has two rigid conical modes in the low speed range. Nevertheless, the system has not been affected by the critical speed in the main operating range.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.2979-2984
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• 2013

This paper proposes a modeling and controller design method of Flywheel Energy Storage System(FESS) for solving the unstable operation problem in hybrid generation system with wind turbine and diesel generator applied in island area. FESS is considered as a permanent magnetic synchronous machine connected to flywheel because of its efficiency. The controller of FESS is composed of AC/DC/AC back-to-back converter. The AC/DC converter is designed to charge/discharge according to the frequency variation and the DC/AC converter to operate to keep the DC bus voltage constant. The proposed modeling and controller design method of FESS was applied to hybrid generation system with wind turbine and diesel generator. The unstable operation problem owing to wind variations was solved through simulation results.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.5
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• pp.443-449
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• 2014

This study aims to develop a Flywheel Energy Storage System (FESS) that uses wind power produced when an urban train is in motion, by utilizing a mounted turbine. This system was designed to generate and store electric power from wind power of a travelling urban train. The flywheel was designed to continue rotation using a one-way clutch bearing installed in the turbine shaft pulley, even in cases where the urban train decelerates or stops. This FESS can generate an additional 44% of electric power in comparison to a system not equipped with a flywheel. The generated power and operational features of the FESS were evaluated and verified through a wind tunnel test. The results show that the electric power stored in the FESS could supply auxiliary power for urban train components or service equipment, such as charging mobiles, Wi-Fi modules, and electric lights.