Youn-Ok Choi

Performance analysis of the DTC using a closed loop stator flux observer for induction motor in the low speed range

Direct torque control (DTC) of an AC motor has the fast torque and flux dynamic responses even though it has very simple scheme to implement. However, DTC do not show good performance at low speed range with conventional open loop stator flux observer when stator resistance varied. Therefore, authors propose a new nonlinear stator flux observer in order to estimate the stator flux of induction motor at low speed and show its simulation results.

A Study of the PV System for Optimum Design Methods With Loss Parameter Compensation

Photovoltaic systems utilize the infinite clean energy of the sun, without creating any air pollution or noise and mechanical vibration. A PV system operates without the need of fuel, rotation surfaces, high temperatures or high pressures. It is therefore to do maintain and simple to install as well as having a long life cycle. The global market for PV systems continues to grow rapidly by 30[%] per year. This paper suggests a new design method for the PV system installation that will allow to the improvement of system efficiency. This method is in accordance with the loss parameter compensation method designed for the PV systems and investigated through simulation and practical experimentation. It was applied to an interconnected 10[㎾] grid PV system and was demonstrated in the field. Features such as solar array, KS, system efficiency, performance and stability were considered. Through the proposed optimal parameter design method, the features of the system were studied, and the 10[㎾] PV system was demonstrated and analyzed.

Performance assessment of 3kW grid-connected PV Systems in Korea

In this paper, for the field test of the first photovoltaic (PV) systems in Korea, the performance of a 3kW grid-connected PV systems for house, separately installed in the solar energy demonstration research complex, had been analyzed for the four years from January 2003 to December 2006.

Single-phase five-level buck-boost inverter

This paper proposes a single-phase five-level buck-boost inverter with a combination of Z-source network and T-type inverter. The proposed inverter has the following advantages as reducing a number of switches, buck-boost voltage with single-stage conversion and shoot-through immunity. In this paper, operating principle, circuit analysis and PWM control are presented. Simulation and experimental results are shown to verify the validity of the proposed inverter and control strategy.

A three-phase cascaded H-bridge quasi switched boost inverter for renewable energy

Recent years, multilevel inverters have become more attractive for researchers due to low total harmonic distortion (THD) in the output voltage and low electromagnetic interference (EMI). This paper proposes a three-phase cascaded H-bridge quasi-switched-boost inverter (CHB-qSBI). The advantages of the proposed inverter are as follows: buck-boost voltage with single stage power conversion, reduced passive components and shoot-through immunity. Furthermore, the dc-link voltage of each module can be controlled by individual shoot-through duty cycle to achieve the same values. Therefore, the proposed inverter solves the imbalance problem of the dc-link voltage in the traditional inverter. The operating principle and control strategy for the proposed inverter are presented. The simulation results are shown to verify the operating principle of the three-phase cascaded H-bridge quasi-switched-boost inverter.

Newton Method MPPT Control and Soft Switching Converter Simulation for Improving the Efficiency of PV System

Abstract - In this paper proposes the soft-switching boost converter and MPPT control for improving the efficiency of PV system. The proposed converter designed H-bridge auxiliary resonant circuit. By this circuit, all of the switching devices perform the soft switching under the zero voltage and zero current condition. Therefore the periodic switching losses can be decreased at turn on, off. The soft switching boost converter designs for 1.5[kW] solar module of the power conversion. Thus, this soft switching boost converter is simulated by MATLAB simulation using Newton-Method algorithm. As a result, Proposed Soft Switching Converter compared to a typical boost converter switching loss was reduced about 61%. And the overall system efficiency was verified to increase about 3.3%.Key Words : Newton-Method, Boost Converter, Psim, Solar Cell * 준 회 원 : 조선대 공대 전기공학과 석사과정 ** 정 회 원 : 조선대 공대 전기공학과 초빙객원교수․공박 *** 시니어회원 : 조선대 공대 전기공학과 교수․공박 ✝ 교신저자, 정회원 : 조선대 공대 전기공학과 겸임교수․공박E-mail: space122@chosun.ac.kr접수일자 : 2011년 10월 17일최종완료 : 2011년 11월 26일

A Study on the PI Controller of AC Servo Motor using Genetic Algorithm

Recently, G.A studies have studied and demonstrated that artificial intelligence like G.A networks, G.A PI controller. The design techniques of PI controller using G.A with the newly proposed teaming algorithm was presented, and the designed controller with AC servo motor system. The goal of this paper is to design the AC servo motor using genetic algorithm and to control drive robot. And in this paper, we propose a genetic algorithms approach to find an optimal or near optimal input variables for genetic algorithm PI controller. Our experimental results show that this approach increases overall classification accuracy rate significantly. Finally, we executed for the implementation of high performance speed control system. It is used a 16-bit DSP, IMS320LF2407, which is capable of the high speed and floating point calculation.