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김동욱(D.U.Kim),신현주(HJ.Shin),류승표(S.P.Ryu),민병권(B.C.Min) 전력전자학회 2001 전력전자학술대회 논문집 Vol.2001 No.7
This paper describes the implementation of UPS system controlled by the DSP. The digital techniques have been used to overcome the problems of UPS system controlled by analog control circuits. By developing these systems using the digital technique we could increase the reliability and improve the electrical characteristics. And we designed and developed the system which is able to control UPSs and to monitor errors, statuses and actual values transmitted from UPS through internet<br/> The UPSs also impose high demands on battery life time, reliability and energy-efficiency. These requirements can only be met by employing sophisticated battery management system(BMS).<br/> Therefore, a highly accurate, universal and inexpensive measuring system for BMS was developed.
김동욱(D.U.Kim),김연풍(Y.P.Kim),신현주(H.J.Shin),백병산(B.S.Baek),류승표(S.P.Ryu),민병권(B.G.Min) 전력전자학회 1999 전력전자학술대회 논문집 Vol.- No.-
When several UPSs are connected in parallel, individual UPS should take charge of exactly same load current Because the output impedance of each UPSs is very low, small voltage difference among them will give rise to circulating current will bring about the decrease of UPS own capacity.<br/> In order to solve this problem in this paper an inverter controller for the UPS which has a good response characteristic and robustness for directly applying in industrial world is proposed. This paper also describes that difference between load current divided by number of operating inverters and its own current is detected as unbalanced current Then frequency and voltage are controlled to minimize the active component and the reactive component respectively. A good controller load-sharing technique is verified by experiments in the parallel poerating system with 40kVA UPSs.
발사체 기저 유동 해석을 위한 2-방정식 난류 모델의 압축성 보정
김동욱(D.U. Kim),박재형(J.H. Park),이승수(S. Lee) 한국전산유체공학회 2022 한국전산유체공학회지 Vol.27 No.1
Explicit compressibility correction methods have been applied to two-equation RANS turbulence models for analyzing the base flow and the entire flow field of a projectile. First, supersonic base flow at a specific Mach number has been analyzed to compare performances of the various compressibility corrections. Base flows at various Mach numbers and Reynolds numbers with Ristorcelli’s compressibility correction applied to κ-ω SST model have been computed, and compared with the experimental results. Lastly, transonic flow analyses of a secant-ogive-cylinder projectile have been performed with Ristorcelli’s compressibility correction. It is found that Ristorcelli’s compressibility correction gives considerable improvement in predicting the base pressure and drag at various flow conditions.