• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.8
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• pp.27-34
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• 2012

This paper proposes variable incremental conductance(IC) algorithm for maximum power point tracking(MPPT) control of photovoltaic. The conventional perturbation & observation(PO) and IC MPPT control algorithm generally uses fixed step size. A small step size reduces a tracking error in the steady state but slows a tracking speed in the transient state. Also, a large step size is fast a tracking speed but increases a tracking error. Therefore, this paper proposes variable IC MPPT algorithm that adjust automatically step size according to operating conditions. To improve a tracking speed and accuracy, when operating point is far from the maximum power point(MPP), the step size uses maximum value and when a operating point is near from the MPP, the step size uses variable step size that adjust according to slope of P-V curve. The validity of MPPT algorithm proposed in this paper prove through compare with conventional PO and IC MPPT algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.45.1-45
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• 2001

This paper proposes a Mamdani fuzzy PID controller for controlling a process with small dead time. The controller composes of a parallel structure of fuzzy PI controller and fuzzy PD controller. Each controller has two inputs, error and change of error. Hence, the control signal of the proposed controller is the average value of the output of the fuzzy PI and PD controllers. The Mamdani fuzzy PID controller is easily to be adjusted to meet the desired control system performances both in transient state and steady state. The simulation results of the proposed Mamdani fuzzy PID controller by using the same parameters (proportional gain, integral time and derivative time) as the conventional PID controller are shown. The response of the Mamdani fuzzy PID control system is faster than the conventional PID control system. Both system responses have ...

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.86-88
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• 1995

This paper presents a design technique of the fuzzy PID controller for power system stabilization. PID parameters of the fuzzy PID controller was self-tuned by the fuzzy inference algorithm. The Nosed controller compare with conventional power system stabilizer(PSS) under various of initial value of rotor angle deviation and load condition. The related simulation results show that the Nosed controller was more excellent control characteristics than conventional PSS in transient-state and steady-state response.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.628-633
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• 2003

An analysis on the steady-state has been made of flow of a compressible fluid rapidly-rotating in a pipe. The flow is induced by an small arbitrary azimuthally-varying thermal forcing added on the basic state of rigid body isothermal rotation. The system Ekman number is assumed to be very small value. Analytic solutions have been obtained for axisymmetric and non-axisymmetric types, in which the axisymmetric solution comes from the azimuthally-averaged wall boundary condition and the non-axisymmetric solution from fluctuating wall boundary condition.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.05a
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• pp.228-231
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• 2000

A hybrid fuzzy controller by means of the genetic algorithms is presented. The control input for the system in the HFC is a convex combination of the FLC's output in transient state and PlD's output in steady state by a fuzzy variable. The HFC combined a PID controller with a fuzzy controller concurrently produces the better output performance than any other controller. A auto-tuning algorithms is presented to automatically improve the performance of hybrid fuzzy controller using genetic algorithms. The algorithms estimates automatical Iy the optimal values of scaling factors, PID parameters and membership function parameters of fuzzy control rules. Especially, in order to auto-tune scaling factors and PID parameters of HFC using GA three kinds of estimation modes are effectively utilized. The HFCs are applied to the second process with time-delay. Computer simulations are conducted at step input and the performances of systems are evaluated and also discussed in ITAE(Integral of the Time multiplied by the Absolute value of Error ) and other ways.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.80-81
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• 2013

유도전동기의 전류 제어 시 PWM(Pulse Width Modulation)이 만들어 낼 수 있는 전압 크기의 제한으로 인해 전류 제어기의 출력과 유도전동기에 입력되는 값이 다를 수 있다. 이로 인해 windup현상이 발생하게 되고, 이는 느린 정착 시간 및 큰 오버슈트와 같은 제어기 성능 저하를 야기 시킬 뿐만 아니라 심각할 경우 시스템의 불안정을 초래한다. 따라서 본 논문에서는 유도전동기의 전류 제어 성능을 개선하기 위해 새로운 anti-windup PI 전류 제어 방법을 제안하고, 실험을 통해 증명한다.

• Journal of Information Processing Systems
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• v.13 no.5
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• pp.1358-1371
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• 2017

Dynamic thermal rating (DTR) system is an effective method to improve the capacity of existing overhead line. According to the methodology based on CIGRE (International Council on Large Electric systems) standard, ampacity values under steady-state heating balance can be calculated from ambient environmental conditions. In this study, simulation analysis of relations between parameters and ampacity is described as functional dependence, which can provide an effective basis for the design and research of overhead transmission lines. The simulation of ampacity variation in different rating scales is described in this paper, which are determined from real-time meteorological data and conductor state parameters. To test the performance of DTR in different rating scales, capacity improvement and risk level are presented. And the experimental results show that the capacity of transmission line by using DTR has significant improvement, with low probability of risk. The information of this study has an important reference value to the operation management of power grid.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.520-523
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• 2004

A phase-locked loop control system designed by using the linear quadratic regulator approach is presented in this paper. The system thus designed is optimal system when system is in locked state and the parameter value of loop filter which is an active PI filter can be obtained easily. By considering the structure of loop filter of phase-locked loop is included in the process to be controlled, a type 1 servo system can be constructed when voltage control oscillator is considered as an integrator. The integral gain of the proposed system obtained by linear quadratic regulator approach can be used as an optimal value to design the parameter of loop filter. The implemented result in controlling the second-order lag pressure process by using the proposed scheme show that the system response is fast with no overshoot and no steady-state error. Furthermore, the experimental results are also shown in term of output disturbance effect rejection, tracking and process parameter changed.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.2
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• pp.50-57
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• 2016

The study presents structural integrity assessment of ductility degradation of a baffle former assembly by performing finite element analysis considering real loading conditions and stress triaxiality. Variations of fracture strain curves of type 304 austenitic stainless steel with stress triaxiality are derived based on the previous study results. Temperature distributions during normal operation such as heat-up, steady state, and cool-down are calculated via finite element temperature analysis considering gamma heating and heat convection with reactor coolant. Variations of stress and strain state during long operation period are also calculated by performing sequentially coupled temperature-stress analysis. Fracture strain is derived by using the fracture curve and the stress triaxility. Finally, variations of ductility degradation damage indicator with the fracture strain and the equivalent inelastic strain are investigated. It is found that maximum value of the ductility degradation damage index continuously increases and becomes 0.4877 at 40 EFPYs. Also, the maximum value occurs at top and middle inner parts of the baffle former assembly before and after 20 EFPYs, respectively.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.195-198
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• 1997

This paper proposes the effective compensation method of the rotor time constant of induction motor. An indirect vector control method is highly dependent on the motor parameters. To solve the problem of performance degradation due to parameter variation in an indirect vector control of induction motor, we compensate the rotor time constant by current error feedback. The proposed method is a simple on-line rotor time constant compensation method using the information from terminal voltages and currents. As the current error, difference between current command and estimated current, approaches to zero, the value of rotor time constant in an indirect vector controller follows the real value of induction motor. This scheme is valid transient region as well as steady state region regardless of low or high speed. This method is verified by computer simulation. For this, we constructed the simulation model of induction motor, indirect vector controller and current regulated PWM (CRPWM) voltage source inverter (VSI) using SIMULINK in MATLAB.