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Hyoungwoo Kim,Joon Young Choi 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10
A robust backstepping controller with nonlinear damping is designed for a back-to-back pulse width modulation converter in doubly fed induction generator for wind energy conversion systems under harmonically distorted grid voltage. The designed controller achieves the exponential ultimate boundedness of the DC-link voltage fluctuation with an arbitrarily fast decay rate and an arbitrarily small bound in the presence of harmonically distorted grid voltage. A desirable feature that distinguishes the proposed controller from other existing controllers is that the proposed controller is able to perform both the normal control operation and grid fault with a single reference input, and it is constructed only by static feedback of measured states. As a result, the control input becomes smooth and easy to implement without requiring of differentiation or switching operations that occur the chattering effect. The exponential boundedness and performance of the designed controller are demonstrated by simulation using SimPowerSystems in Matlab and compared with a proportional-integral controller.
Effects of Hybrid Multi-Stacking of BSCCO Wires and YBCO Wires on AC Loss
Hyoungwoo Lim,Gueesoo Cha,Heejoon Lee Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>The multi-stacked wires which are made of one type of wires, YBCO wires or BSCCO wires, are being currently used in superconducting machines. Property of hybrid multi-stacked (HMS) wire made of the combination of YBCO wire and BSCCO wire can be different from the uniform multi-stacked (UMS) wire. This paper presents the magnetization losses of HMS wires which were made of YBCO wires and BSCCO wires. HMS 2 stacked (YB) wire and HMS 4 stacked (YYBB, YBYB, YBBY and BYYB) wires were tested. Y and B stand for YBCO wire and BSCCO wire, respectively. The YBCO wire and the BSCCO wire which had similar width were chosen to fabricate the UMS wires and HMS wires. The losses of the HMS wires were compared with the loss of UMS wires. According to the measurement results of the HMS 2 stacked wire and HMS 4 stacked wires, the loss of HMS wire was between the loss of UMS BSCCO and UMS YBCO wire at low magnetic field and it was almost the same with those of UMS BSCCO and UMS YBCO wire at high magnetic field.</P>
Calculation Method for Cold Flow Stress of Al6082 Based on Tensile Test and Compression Test Results
Hyoungwoo Lee,Jae-Hong Yoo,Yong chul Kwon,Jong-Hun Kang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.8
A method to obtain flow stress in the plastic deformation state is investigated in this study. The flow stress prior to necking is calculated based on Hollomon’s constitutiveequation using the strain rate and stress obtained from a tensile test, whereas the strain hardening coefficient after necking is obtained using the stress and strain rateobtained from a compression test; subsequently, the two flow stresses are combined. Two-dimensional rigid plastic finite element analysis considering ductile fracture in the stress test is conducted by inputting the proposed flow stress. It is confirmed that the shape and dimensions of the necking part on the load–displacement curve from the finite element analysis are similar to those obtained experimentally, thereby confirming the validity of the proposed flow stress calculation.
A study on high speed coupling design for wind turbine using a finite element analysis
HyoungWoo Lee,한정영,강종훈 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.8
The purpose of this study is to design a high speed coupling for 3 MW wind turbines and evaluate its structural stability. A basic analysis was performed to assess the structural stability of two materials, SPS6 steel plate and a composite material (Glass7628, Glass/Epoxy), in relation to misalignment in the axial and radial directions. The entire model was analyzed for a high speed coupling based on the SPS6 steel plate, which was found to have higher stability among the two materials, and safety factors were estimated for various levels of power delivery. To test the proposed high speed coupling design, a performance test was carried out to verify the stability of the final product.