• Proceedings of the IEEK Conference
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• 2000.11b
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• pp.95-99
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• 2000

New locking algorithm of DLL is proposed to improve the locking speed and low power dissipation in this paper, In spite of using the architecture of delay controller, low power consumption is acquired by operating only one controller at once and fast locking speed is accomplished by initial setting from the coarse controller. The proposed DLL circuit is operated from 50MHz to 200MHz and locked within 6 cycle at all of operating frequency.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.8
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• pp.52-59
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• 1998

New types of PFD (phase-frequency detector) are proposed with reset time and propagation delay reduced. The perfomrance of our proposed PFDs are confirmed by SPICE simulation with 0.8.mu.m CMOS process parameter. As a result of simulation, the reset time of PFDs are 0.32 nsec and 0.030 nsec in capture-process. The proposed PFDs can be used in hihg-speed phase-licked loop (PLL).

• Journal of Korean Society of Transportation
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• v.20 no.5
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• pp.163-174
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• 2002

Speeding has been reported as one of the major causes for fatal traffic accidents in Korea. The resolution against this dangerous speeding comes to make the automated speed enforcement system an enforcement tool. The speed detection device, which measures speeds of each incoming vehicles using double loop sensors, requires high accuracy. The object of this study is to develop an accurate speed measurement algorithm using double loop detectors. Some important findings are summarized as follows: 1) It was found that speed measurement errors are caused by scanning rate, distance of two loops, irregular vehicle trajectories, multiple vehicles in detection zone. 2) A proposed algorithm using two signal set proved to reduce variance as well as mean of speed measurement. 3) A proposed filtering algorithm was effective to filter irregular driving vehicles and multiple vehicles in detection zone. A comprehensive field test of developed algorithm resulted in significant improvement of speed measurement accuracy.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1358-1366
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• 2015

This study focuses on an advanced second-order sliding mode control strategy for a variable speed wind turbine based on a permanent magnet synchronous generator to maximize wind power extraction while simultaneously reducing the mechanical stress effect. The control design based on a modified version of the super-twisting algorithm with variable gains can be applied to the cascaded system scheme comprising the current control loop and speed control loop. The proposed control inheriting the well-known robustness of the sliding technique successfully deals with the problems of essential nonlinearity of wind turbine systems, the effects of disturbance regarding variation on the parameters, and the random nature of wind speed. In addition, the advantages of the adaptive gains and the smoothness of the control action strongly reduce the chatter signals of wind turbine systems. Finally, with comparison with the traditional super-twisting algorithm, the performance of the system is verified through simulation results under wind speed turbulence and parameter variations.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.83-85
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• 2003

This paper presents a speed control of permanent magnet synchronous motors (PMSM) using an adaptive integral binary observer without speed and position sensors. In view of composition with a main loop regulator and an auxiliary loop regulator, the binary observer has a property of the chattering alleviation in the constant boundary layer. In order to improve the steady state performance of the binary observer, the proposed adaptive integral binary observer is formed by adding extra integral dynamics to the switching hyperplane equation. The effectiveness of the proposed system is conformed by the experimental results.

• Journal of Power System Engineering
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• v.10 no.3
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• pp.81-87
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• 2006

This paper deals with an empirical model for decoupling control to control the refrigeration system effectively. The conventional control schemes of the system are mainly focused on representative two control methods, superheat control and capacity control. The capacity control is basically conducted to respond partial loading conditions on the purpose of energy saving. The superheat control is mainly carried out to maintain maximum coefficient of performance (COP). In the variable speed refrigeration system, the capacity and the superheat are controlled by inverters and electronic expansion valves respectively for saving energy and improving cost performance. The capacity and superheat can not be controlled independently because of interfering loop when the compressor speed and opening angle electronic expansion valve is varied. Therefore, we suggest decoupling model to eliminate the interfering loop at first. Next, each transfer function in decoupling control model is obtained from number of experiments.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.465-465
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• 2000

The paper presents the fuzzy control technique to adjust the gain schedule in the fuzzy controller. The micro computer is designed to the fuzzy controller to execute the proportional gain with the data of the error and speed command. The gain schedule is the fuzzy set which execute based on the fuzzy rule. The gain schedule from the fuzzy controller is fed to the sinusoidal pulse width modulation (SPWM) inverter for control the response and speed of the induction motor. The induction motor coupling to the DC motor and tachogenerator which DC motor as a load. The test result of the fuzzy control technique in the open loop control, it provides a good response and in the closed loop control it can control speed in the any condition of load design

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.54 no.2
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• pp.73-79
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• 2005

This paper is proposed hybrid artificial intelligent (HAI) controller based on the vector controlled induction motor drive system. The hybrid combination of fuzzy control and neural network will produce a powerful representation flexibility and numerical processing capability. Also, this paper is proposed speed estimation of induction motor using a closed-loop state observer. The rotor position is calculated through the stator flux position and an estimated flux value of rotation reference frame. A closed-loop state observer is implemented to compute the speed feedback signal. The results of analysis prove that the proposed control system has strong robustness to rotor parameter variation, and has good steady-state accuracy and transitory response.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1046-1049
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• 2000

A direct torque control(DTC) based sensorless speed control system which employs a new closed loop flux observer is proposed. The flux observer is an adaptive gain scheduling observer where motor speed is used as the scheduling variable. Adaptive nature comes from the fact that the estimates of stator resistance and speed are included as observer parameters. Simulation results show that the proposed flux observer gives better control and estimation results than conventional flux estimator specially in low speed region.

• Journal of Power Electronics
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• v.4 no.2
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• pp.65-76
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• 2004

In this paper, the steady-state analysis of the three-phase self-excited induction generator (SEIG) driven by a variable-speed prime mover (VSPM) such as a wind turbine is presented. The steady-state torque-speed characteristics of the VSPM are considered with the three-phase SEIG equivalent circuit for evaluating the operating performances due to the inductive load variations. Furthermore, a PI closed-loop feedback voltage regulation scheme based on the static VAR compensator (SVC) for the three-phase SEIG driven by the VSPM is designed and considered for the wind power generation conditioner. The simulation and experimental results prove the practical effectiveness of the additional SVC with the PI controller-based feedback loop in terms of fast response and high performances.