• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2475-2477
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• 1999

This paper describes a simulation model and scaled hardware model to analyze the dynamic performance of Unified Power Flow Controller, which adjust flexibly the active and reactive power flow through the ac transmission line. The design of control system was developed using vector control method. The results of simulation and scaled hardware test show that the developed control system works accurately. And both models are very effective to analyze the dynamic performance of the Unified Power Flow Controller.

• 연구논문집
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• s.26
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• pp.85-94
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• 1996

The purpose of this study is to bring out the optimal design factors which effect on dynamic characteristics in the design of proportional flow control valve with high response characteristics, and to verify the validity of the design factors. In this study, force feedback type flow control valve with nozzle-flapper is studied. And, the influences which fixed orifice, nozzle diameter, and maximum displacement between nozzle and flapper effect on dynamic characteristics are analyzed. We have done simulations using the optimal design factors and simulink(Matlab) as a simulation tool, and verified the validity of our simulations by means of comparison our simulation results with an experimental results of another similar valve.

• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.3 s.22
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• pp.11-17
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• 2005

In this paper, the mathematical model of the underwater discharge system using a linear pump is derived and the suitable opening pattern of a flow control valve which satisfies the discharge performance requirements is obtained through the underwater discharge simulations. The simulation results show that the dynamic characteristics of a projectile are greatly affected by the opening pattern of the flow control valve, however, hardly by the diving depth. It is anticipated that the simulation model can be used to derive the design parameters and analyze the performance of the designed underwater discharge system using a linear pump.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.3
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• pp.170-178
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• 2007

Rapid increases in the concentrations of greenhouse gases and many other chemically important trace gases have occurred over the last several centuries. For understanding the roles of these important gases in global change, it is essential to identify their sources and sinks, to characterize biogenic gas fluxes between the biosphere and atmosphere, and to understand the processes that control them. In this paper, enclosure-based measurements are described in a practical manner for field experiments. Theoretical reviews of mass balance equation in the enclosure and sensitivity of the flow-through dynamic flux chamber technique are presented; specifically for the case of NO flux measurements from soil surface. The physical system and theory behind the flow-through dynamic flux chamber method are examined. New calculation flux formula was introduced by considering NO chemical loss on chamber wall and uncertainties of the NO flux calculation were discussed.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.49-58
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• 2018

This paper introduces a research on the control method design for the subsonic intake flow of a dual-combustion ramjet engine. To design the control method, the intake flow dynamic response characteristics, based on a designated flow condition and intake geometry, are investigated, and a control method concept considering the intake flow characteristics is established. Using a dynamic simulation model of a dual-combustion ramjet, control input/output linearized models are obtained such that a control loop design based on linearized models can be accomplished. Finally, from various control loop simulations, the performance of the control method, including its control loop stability, is evaluated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.10-17
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• 2004

To achieve the advanced forward flight performance of helicopter, the passive control methods for enhancement of the dynamic stall characteristics of rotor blades are studied. To enhance the dynamic stall characteristics of the rotor blades, it is essential to improve the lift performance and the pitching moment performance simultaneously with the control of the separation on the rotor blades. For this point of view, both the fixed droop leading edge and the Gurney flap which are simply realized are used for control of the dynamic stall in severe dynamic stall conditions. From this study, the combination of both passive control methods showed dramatic enhancement of lift and pitching moment performance in dynamic stall than previous research results.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.70.2-70
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• 2002

In the thermal power plant, it is difficult to maintain strict control of the steam temperature in order to avoid thermal stress, because of variation of the heating value according to the fuel source, the time delay of changes in main steam temperature versus changes in fuel flow rate, difficulty of control on the main steam temperature control and the reheater steam temperature control system owing to the dynamic response characteristics of changes in steam temperature and the reheater steam temperature, fluctuation of inner fluid water and steam flow rates widely during load-following operation. Up to the present time, the PID controller has been used to operate this system...

• International Journal of Control, Automation, and Systems
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• v.6 no.4
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• pp.495-505
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• 2008

This paper describes modeling Voltage Sourced Inverter (VSI) type Flexible AC Transmission System (FACTS) controllers and control methods for power system dynamic stability studies. The considered FACTS controllers are the Static Compensator (STATCOM), the Static Synchronous Series Compensator (SSSC), and the Unified Power Flow Controller (UPFC). In this paper, these FACTS controllers are derived in the current injection model, and it is applied to the linear and nonlinear analysis algorithm for power system dynamics studies. The parameters of the FACTS controllers are set to damp the inter-area oscillations, and the supplementary damping controllers and its control schemes are proposed to increase damping abilities of the FACTS controllers. For these works, the linear analysis for each FACTS controller with or without damping controller is executed, and the dynamic characteristics of each FACTS controller are analyzed. The results are verified by the nonlinear analysis using the time-domain simulation.

• Journal of Drive and Control
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• v.17 no.2
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• pp.55-62
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• 2020

There are two types of IMV for MCV, the spool type and the poppet type. The spool type is used in the existing excavator MCV and easily meets large-capacity flow conditions, but has a flow force problem which affects the spool control. The poppet type stably blocks the flow and has excellent rapid response. However, the larger the capacity, the larger the diameter of the poppet needed, requiring a strong spring to withstand the oil pressure. In this study, a bi-directional three-stage IMV for MCV that can be used in medium and large hydraulic excavators was proposed. This is a poppet type, enabling bi-directional flow control and resolves the problem of proportional solenoid suction force limitation. To investigate the validity of the proposed valve, the system was mathematically modeled and the static and dynamic characteristics were investigated through the simulation using commercial software. It has been concluded that the reverse flow is possible in a regeneration circuit and that the proposed IMV can be used to perform various excavation modes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.8
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• pp.577-584
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• 2007

A variable-flow-rate balancing valve has been developed and optimized to apply to a distributor in a hot-water heating system. Fluid dynamic performance of the system was evaluated by comparing the results with the previous pressure difference control valve (PDCV) system. In view of the variations of pressure drop and flow rate according to the sequential closing of the control valves, the present system which is named "smart system distributor", is very stable without a certain flow rate concentration. The level of pressure drop variation is also low as compared with the previous system with a PDCV. In view of the occurrence of cavitation, the present system is quite superior to the previous system because the instantaneous pressures at all sections are much higher than the vapor pressure. On the other hand, the previous system has a possibility of cavitation when one or more control valves are closed.