• KIPS Transactions on Computer and Communication Systems
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• v.3 no.7
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• pp.209-218
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• 2014

An AP that is used by smart device is going to be complicated because smart devices support diverse functions. As a result, multiple low-level IPs including a dedicated CPU are integrated in a high-level subsystem for supporting complicated function such as multimedia codec and camera. A subsystem has software that executes separately from main system, and the software needs to be initialized for every execution of the subsystem. This causes increase of the subsystem startup time so it should be improved because startup time of subsystem affects launching time of application. Methods in applied to computer system for fast startup also could be applied to fast startup of subsystem because subsystem is similar with computer system. In this paper, we apply snapshot method that is used in computer system to subsystem and analyzes the pros and cons. And snapshot method could not be applied to register of IP without modification because register of IP offers restricted read and write. So this paper suggests technique that applying snapshot to each characteristic of register.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1567-1576
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• 2018

The reliability of grid-connected inverters can be improved by algorithms capable of diagnosing faults in LCL filters. A fault diagnostic method during inverter startup is proposed. The proposed method can accurately generate and monitor information on the peak value and the location of the peak frequency component of the step response of a damped LCL filter. To identify faults, the proposed method compares the evaluated response with the response of a healthy higher-order damped LCL filter. The frequency components in the filter voltage response are first analytically obtained in closed form, which yields the expected trends for the filter faults. In the converter controller, the frequency components in the filter voltage response are computed using an appropriately designed fast Fourier transform and compared with healthy LCL response parameters using a finite state machine, which is used to sequence the proposed startup diagnostics. The performance of the proposed method is validated by comparing analytical results with the simulation and experimental results for a three-phase grid-connected inverter with a damped LCL filter.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.1
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• pp.50-56
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• 2005

This paper develops a sensorless BLDCM drive for frequently startup. The position information is based on detecting the zero-crossing point of the BEMF that can be directly obtained from the terminal voltage of the floating phase without voltage-dividing and filtering. As a result, this approach makes it possible to detect the rotor position over a wide speed range, especially at a lower speed. A fast startup procedure is also discussed because the induced BEMF signals are not present when motor is at rest. Experimental results shows that the schemes implemented are feasible and the performance achieved are satisfactory.

• Journal of Communications and Networks
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• v.16 no.3
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• pp.344-354
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• 2014

Transmission control protocol friendly rate control (TFRC) is designed to mainly provide optimal service for unicast applications, such as multimedia streaming in the best-effort Internet environment. However, high bandwidth networks with large delays present an environment where TFRC may have a problem in utilizing the full bandwidth. TFRC inherits the slow-start mechanism of TCP Reno, but this is a time-consuming process that may require many round-trip-times (RTTs), until an appropriate sending rate is reached. Another disadvantage inherited from TCP Reno is the RTT-unfairness problem, which severely affects the performance of long-RTT flows. In this paper, we suggest enhanced TFRC for high quality video streaming over high bandwidth delay product networks. First, we propose a fast startup scheme that increases the data rate more aggressively than the slow-start, while mitigating the overshooting problem. Second, we propose a bandwidth estimation method to achieve more equitable bandwidth allocations among streaming flows that compete for the same narrow link with different RTTs. Finally, we improve the responsiveness of TFRC in the presence of severe congestion. Simulation results have shown that our proposal can achieve a fast startup and provide fairness with competing flows compared to the original TFRC.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.2
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• pp.138-144
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• 2013

Most of the DC loads have had the sensitive characteristics electrically for input voltage. In this system, power converter is operated after connecting with DC loads to minimize the overshoot of the control voltage that may occur during connection of the loads. But whenever starting the power converter, parameters in circuit are different because power converter has been connected with diverse load types at each startup time. This is cause of a disadvantage to PI controller design of power converter. In this paper, the novel voltage control method using sliding mode control theory has proposed. This control method minimizes the overshoot of control voltage at startup of power converter. Despite the variations of the system parameters, the proposed voltage controller has fast response and robustness characteristics such as PI and sliding mode controllers. The proposed controller was applied to the three-phase AC/DC converter and each performance of controller was verified.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.277-282
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• 2010

Durability of automotive polymer electrolyte membrane fuel cell (PEMFC) strongly depends the startup/shutdown procedure. Formation of hydrogen/air boundary in the anode gas channel, so-called reverse current condition, particularly induces fast degradation of the cathode. Under the reverse current condition, high voltage is present at the cathode facing air in the anode gas channel and is a function of residual oxygen concentration in the gas channels, that increases with storage time and reaches 21% (air) eventually. In this study, effects of residual oxygen concentration in a PEMFC on degradation of the PEMFC.

• Journal of the Korean Society of Safety
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• v.14 no.2
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• pp.52-61
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• 1999

This paper proposes the application of fuzzy control for high performance control of induction motor using electric vehicles. A fuzzy controller converts a set of liguistic rules based on expert knowledge into a automatic control strategy. Such controllers have often been found superior to conventional controllers especially when information being processed is inexact and uncertain. A system with fast torque response is very beneficial in applications where direct self control (DSC) is highly desirable. The response of DSC is slower during startup and during change in command torque. Fuzzy control is used for implementation of DSC to improve its slow response. Simulation implementation of the fuzzy logic controller was carried out to verify the behavior of the controller. The simulation results with fuzzy control are compared with those of the conventional DSC. The starting flux and torque response and the responses to the step changes in command torque with fuzzy implementation show a considerable improvement over the conventional control. The steady state responses in both the cases are the same.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.669-675
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• 1991

Based on process analysis as well as extensive operation experience, two fuzzy expert control algorithms, for startup and control, are proposed for a supercritical fluid extraction process which has high interacting multivariable structure. In the proposed algorithms, a new simple defuzzification method which only requires four fundamental arithmetic rules is also presented. Through numerical simulations, control performance using the proposed control algorithm is compared with that of a different fuzzy algorithm by an other researcher and that of conventional PID-type controllers which are tuned by well-known optimal criteria. Also, the proposed control algorithm has been tested to the bench scale supercritical fluid extraction process. As a consequence, the proposed fuzzy expert controller has shown fast and robust control performance while the other controllers show sluggish and/or highly oscillatory responses.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2301-2303
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• 2003

A steam turnine in thermal/nuclear power plant drives generator and maintains it at rated speed using high temperature and high pressure steam energy. After synchronization in parallel with the power system, generator output increases according as the governor, that is the controller, increases steam flow into turbine. By the way, as the steam flow into turbine can not be reduced fast even though the electrical load is lost, the turbine gets into dangerous situation due to the increase of its speed. At this time, the duty of the turbine governor is to limit the speed to its overspeed trip setpoint by stopping the steam flow as soon as possible, the test of which is called load rejection test. It is introduced in this paper for a simulation test of generator load rejection to be implemented on the turbine governor in a 600MW nuclear power plant before its startup.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1605-1606
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• 2007

An electrical generator in power plant is driven and maintained its speed at rated by steam turbine. By the way, after synchronization in parallel with the power system, as the steam flow into turbine can not be reduced fast even though the electrical load is lost, the turbine gets into dangerous situation due to the increase of its speed. At this time, the duty of the turbine governor is to limit the speed to its overspeed trip set point by stopping the steam flow as soon as possible, the test of which is called load rejection test. It is introduced in this paper for a field simulation test of generator load rejection to be implemented on the turbine governor in a 680MW nuclear power plant before its startup.