• Journal of Institute of Control, Robotics and Systems
• /
• v.15 no.10
• /
• pp.982-987
• /
• 2009

On the controller switching time, even though on-line/off-line controller outputs are the same, a problem which deteriorates the performance of bumpless transfer can happen in case that any discrepancy between the two controller inputs is transferred directly to the controller output. In this paper, we analyze the cause of that phenomenon in existing research results and propose a new method which improves that problem. In order to solve this problem, the off-line controller is augmented to an anti-windup structure and an improved bumpless transfer method is derived by using the changed input of the off-line controller instead of the plant input. We exemplify the performance of the proposed method by comparing with the performance of the existing method via numerical examples.

• Proceedings of the KIPE Conference
• /
• 1998.10a
• /
• pp.668-676
• /
• 1998

A passive energy recovery snubber for high-power-factor boost rectifier, in which the main switch is described in terms of the equivalent circuits that are operational during turn-on and turn-off sequences. These equivalent circuits are analyzed so that the overshoot voltage across the main switch, the snubber current, and the turn-off transition time can be predicted analytically. The main switch combined with proposed snubber can be turned on with zero current and turned off at limited voltage stress. The high-power-factor boost rectifier with proposed snubber is implemented, and the experimental results are presented to confirm the validity of proposed snubber.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.5
• /
• pp.1527-1536
• /
• 2014

This paper investigates the optimal values of turn-on and turn-off angles, and ratio of flux linkage at turn-off angle and peak phase current positions of optimal control for accomplishing maximum output power in an 8/6 Switched Reluctance Generator (8/6 SRG). Phase current waveform is analyzed to determine optimal excitation angles (optimal turn-on and turn-off angles) of the SRG for maximum output power which is applied from a nonlinear magnetization curve in terms of control variables (dc bus voltage, shaft speed, and excitation angles). The optimal excitation angles in single pulse mode of operation are proposed via the analytical model. Simulated and experimental results have verified the accuracy of the analytical model.

• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.137-140
• /
• 2000

This paper proposes an improved soft switching two-transistor forward converter which uses a novel lossless snubber circuit to effectively control the turn-off dv/dt rate of the main transistors. In the proposed soft switching implementation the turn-off voltage traces across the main two transistors are almost the same contributing to reduce the total capacitive turn-on loss and the snubber current is divided into the two transistors resulting in distributed thermal stresses

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.164-167
• /
• 1996

This paper presents an off-line P.I.D parameter estimation method during normal operation in power plant. The process parameters are estimated using the recursive least square method. The controller parameters are estimated on the basis of desired characteristics of the dynamic model of the closed-loop control.

• 한국연소학회:학술대회논문집
• /
• 2004.06a
• /
• pp.7-14
• /
• 2004

The lift-off characteristics of the triple flame have been studied experimentally with various mean velocities and concentration gradients using a multi-slot burner, which can control the concentration gradient and the mean velocity independently, Lift-off height, axial maximum velocity, flame temperature, and some other characteristics were examined for methane and propane flame, It was found that minimum values of the lift-off heights exist at a certain concentration gradient for constant mean velocity, and this result implies that the propagation velocity has a maximum value at this condition, OH radical distribution was measured with LIF method and velocity variation along streamline was measured with PlV system. In addition maximum temperature along streamline was measured with CARS system. The intensity of the diffusion flame affects on the propagation velocity of triple flame in the region of very weak concentration gradient.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.3
• /
• pp.102-111
• /
• 1996

For the air-fuel ratio control in a fuel injection SI engine, the Jump-Ramp control algorithm has been widely adopted by using the on/off type oxygen sensor. But the Jump-Ramp control method has limitation on treating the frequency and amplitude of the air-fuel ratio oscillation. This study suggests another feedback control logic named modulated fuel feedback control, which has a concept of pre-tuned air-fuel ratio oscillation. In the modulation method, the oxygen sensor output is not treated as on/off signal but as analog signal for feedback. By using the modulation method, the frequency and the amplitude of air-fuel ratio oscillation can be adjustable to some extent for improving the conversion efficiency of the Three-Way Catalyst. The result shows that the performance of the modulation method is better than that Jump-Ramp control method in reducing the amplitude of the air-fuel ratio oscillation as well as in increasing the frequency of the air-fuel ratio oscillation.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.6
• /
• pp.1070-1074
• /
• 2010

In this study we deal with a simple computer simulation algorithm to decide the PRT station capacity. PRT system is different from the conventional rail traffic system in such point that the station is off-line so as to guarantee a very short headway. This characteristic has correlation with the accurate prediction of the line capacity and with the scale of the off-line station. In this paper physical factors and vehicles per hour that are necessary to decide the off-line station scale and the off-line station capacity, respectively, are shown through a simple compter simulations.

• Journal of Power Electronics
• /
• v.17 no.3
• /
• pp.716-724
• /
• 2017

The output voltage of an off-grid inverter is influenced by load current, and the voltage harmonics especially the 5th and 7th are increased with nonlinear loads. In this paper, to attenuate the output voltage harmonics of off-grid inverters with nonlinear loads nearby, a load current feedforward is proposed. It is introduced to a voltage control loop based on the Positive and Negative Sequence Harmonic Regulator (PNSHR) compensation to modify the output impedance at selective frequencies. The parameters of the PNSHR are revised with the output impedance of the off-grid inverter, which minimizes the output impedance of the off-grid inverter. Experimental results verify the proposed method, showing that the output voltage harmonics caused by nonlinear loads can be effectively suppressed.

• The KIPS Transactions:PartD
• /
• v.8D no.4
• /
• pp.427-438
• /
• 2001

Recently, Environmental Control Devices of Green House for Protected Cultivation is composed of on/off-type Controller to control each device using timer in equipment of intensive Labor. In case of system, it is difficult to grasp condition of the greenhouse about errors when this system has defect of a hardware, and it operates in the remote place or at night. In this paper, we developed a system that capable of replacing the existing control method of on/off with display panel in the greenhouse, monitoring data aquisition and status in the greenhouse using client computer based on internet. Also this system can communicate with each local greenhouse, and send alarm message about error. And we constructed web server to manage efficient informations for environmental control and corps cultivation in the greenhouse.