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정세교 慶尙大學校 工科大學 自動化및컴퓨터應用技術硏究所 1998 自動化 및 컴퓨터應用技術 Vol.5 No.1
A new current control technique is presented for three phase PWM inverter-fed AC drives. The features of several existing approaches are analyzed and a variable structure control(VSC) with an integral action, so called an integral variable structure control(IVSC), is proposed as an effective way of realizing the high performance current control. The control characteristics of the proposed IVSC are investigated had the design method is presented for the AC drives associated with a voltage-fed PWM inverter. By employing the proposed control, a robust control performance against the uncertainties of the machine parameters is obtained in both transient and steady state. The proposed control is applied to the three phase squirrel cage induction machine drives and the improvement of the control performance is well demonstrated through the simulations and experiments.
광자 크리스탈 채널드롭 터널링을 이용한 파장분할 소자에 대한 연구
鄭敎龐,吳世澤 弘益大學校 科學技術硏究所 2003 科學技術硏究論文集 Vol.14 No.-
We design a 1 X 4 wavelength demultiplexer based on channel drop tunneling in photonic crystals. We show the results of simulation of the demultiplexer device for tunneling properties of electromagnetic waves in a two-dimensional photonic crystal, with an application of the finite-difference time-domain method with perfectly-matched-layer absorbing boundary condition. We find four frequencies at which the channel drop tunneling occurs, and design a 1 X 4 wavelength demultiplexer based on the frequencies. To improve the channel drop transmission, we separate spurious reflections in photonic crystal waveguide simulations using a large computational domain, and obtain the results of highly efficient transmission.
接木한 배나무의 樹齡에 따르는 燐酸의 消長에 대한 硏究
金晙敎,元世鎬,安鶴洙,鄭熙敦 건국대학교 1968 學術誌 Vol.9 No.1
It is very essential problem that the study on the translocation of nutritious substances between the scion and the stock when the seedlings were grafted. So the present experiments was carried out to investigate the behavior of phosphorous in the leaves, stems, new shoots and roots of scion and stock for the different age of tree after the pear-tree was grafted. For the study the seedlings were raised in the green-house of Agr. and Indus. college of Kon-kuk University. The results obtained from this work may be summarized as follows. ① The Phosphosrous contents in leaves, 2 to 3 year grafted-pear was slightly increased as compare with the same year-old stock. ② The phosphorous contents in the new shoots, one year grafted-pear was markedly decreased as compare with the same year-old stock. However 2 year-old galled-pear was gently increased. ③ The phosphorous contents in the stem and roots, there is no different between the grafted-pear (scion) and stock without relation to the age of tree.
UPS 응용을 위한 3상 PWM 인버터의 새로운 전압 제어 방법
박남주,임철우,정세교,이영조 慶尙大學校 工科大學 自動化및컴퓨터應用技術硏究所 1999 自動化 및 컴퓨터應用技術 Vol.6 No.1
This paper describes a novel control method of a three-phase PWM inverter for uninterruptible power supply(UPS) applications. To obtain the fast dynamics and excellent harmonic characteristics, a new state feedback control technique is proposed. The proposed control consists of the inner-loop current and outer-loop voltage controllers with a load current estimator to reduce the effects of the load variations and nonlinearity. In order to verify the effectiveness of the proposed control, the simulation is carried out for various load condition.
Phase-Locked Loop for Grid-Connected Three-Phase Power Generation Systems
Se-Kyo Chung 한국정보과학회 1999 Journal of Electrical Engineering and Information Vol.4 No.6
Analysis and design of a phase-locked loop(PLL) are presented for the power factor control of grid-connected three-phase power generation systems. The dynamic characteristics of the closed loop PLL system with a second order is investigated and the optimization method is discussed. In particular, the performance of the PLL in the three-phase system is analyzed in the distorted utility conditions such as the phase unbalancing, harmonics, and offset caused by the nonlinearities and measurement errors. The PLL technique for the three-phase system is implemented in software of a digital signal processor(DSP) to verify the analytic results and the experiments are carried out for various utility conditions. Finally, this technique is applied to the grid-connected photovoltaic power generation system with the current-controlled PWM inverter. The experimental results well show its phase tracking capability in the three-phase grid-connected operation.
A New Instantaneous Torque Control of PM Synchronous Motor for High Performance Direct Drive Systems
Se-Kyo Chung,Hyun-Soo Kim,Chang-Gyun Kim,Myung-Joong Youn 전력전자학회 1996 전력전자학술대회 논문집 Vol.1996 No.-
A new Instantaneous torque control technique is presented for a high performance control of a permanent magnet synchronous motor Using the model reference adaptive system technique, the linkage flux of the motor IS estimated and the torque IS instantaneously controlled by the proposed torque controller combining With a variable structure control and space vector PWM The proposed torque control provides the advantage of reducing the torque pulsation caused by the flux harmonics This control strategy is applied to the high torque PM synchronous motor drives for direct drive systems and is Implemented by using a software of the DSP TMS320C30 The experiments are earned out for this system and the results well demonstrate the effectiveness of the proposed control.
Design of Bootstrap Power Supply for Half-Bridge Circuits using Snubber Energy Regeneration
Chung, Se-Kyo,Lim, Jung-Gyu The Korean Institute of Power Electronics 2007 JOURNAL OF POWER ELECTRONICS Vol.7 No.4
This paper deals with a design of a bootstrap power supply using snubber energy regeneration, which is used to power a high-side gate driver of a half-bridge circuit. In the proposed circuit, the energy stored in the low-side snubber capacitor is transferred to the high-side bootstrap capacitor without any magnetic components. Thus, the power dissipation in the RCD snubber can be effectively reduced. The operation principle and design method of the proposed circuit are presented. The experimental results are also provided to show the validity of the proposed circuit.