• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.4
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• pp.149-156
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• 2022

Magneto-Rheological Fluid (MRF) is a functional fluid in which flow characteristics change into magnetic force due to its magnetic particles. When the semi-active control device does not use MRF for a long time, precipitation of magnetic particles and abnormal control force occur. Thus, Electro Magneto-Rheological Fluid (EMRF), which improves the precipitation of magnetic particles for MRF and exhibits existing control performance, was developed in this study. First, the optimal mix proportion ratio was selected by conducting a precipitation experiment and a controlled force test by varying the content of grease based on the existing MRF components. Also, EMRF was applied to the shear-type damper to evaluate the control performance when applied to the control device. The cylinder-type damper was developed to apply to the structure, and control performance evaluation was conducted. The result confirmed that the precipitation of the magnetic particles was improved, while the damper using EMRF exhibited excellent control performance.

• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2211-2220
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• 2015

This paper analyzes multiple active management (AM) techniques of active distribution network (ADN), and proposes an optimal coordination model of intermittent distributed generation (IDG) accommodation considering the timing characteristic of load and IDG. The objective of the model is to maximize the daily amount of IDG accommodation under the uncertainties of IDG and load. Various active management techniques such as IDG curtailment, on-load tap changer (OLTC) tap adjusting, voltage regulator (VR) tap adjusting, shunt capacitors compensation and so on are fully considered. Genetic algorithm and Primal-Dual Interior Point Method (PDIPM) is used for the model solving. Point estimate method is used to simulate the uncertainties. Different scenarios are selected for the IDG accommodation capability investigation under different active management schemes. Finally a modified IEEE 123 case is used to testify the proposed accommodation model, the results show that the active management can largely increase the IDG accommodation and penetration.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.425-433
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• 1999

This paper describes a simulation model and a scaled hardware model to analyze the dynamic performance of Unified Power Flow Controller, which can flexibly adjust 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.

• Journal of Electrical Engineering and Technology
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• v.4 no.3
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• pp.315-322
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• 2009

Penetration and installation of a new dynamic technology known as Flexible AC Transmission Systems (FACTS) in a practical and dynamic network requires and force expert engineer to develop robust and flexible strategy for planning and control. Unified Power Flow Controller (UPFC) is one of the recent and effective FACTS devices designed for multi control operation to enhance the power system security. This paper presents a dynamic strategy based on Particle Swarm Optimization (PSO) for optimal parameters setting of UPFC to enhance the system loadability. Firstly, we perform a multi power flow analysis with load incrementation to construct a global database to determine the initial efficient bounds associated to active power and reactive power target vector. Secondly a PSO technique applied to search the new parameters setting of the UPFC within the initial new active power and reactive power target bounds. The proposed approach is implemented with Matlab program and verified with IEEE 30-Bus test network. The results show that the proposed approach can converge to the near optimum solution with accuracy, and confirm that flexible multi-control of this device coordinated with efficient location enhance the system security of power system by eliminating the overloaded lines and the bus voltage violation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.527-528
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• 2012

DBD (Dielectric Barrier Discharge) plasma actuator was designed for aerodynamic drag reduction using plasma flow control, and the drag reduction was measured by wind-tunnel tests using 2D test model. At the zero wind velocity, the plasma flow control had no effect on the drag reduction because the flow separation and surface friction drag were not occurred. At the wind velocity of 2m/s, 9.7% of drag was reduced by the flow separation control. The drag reduction decreased as the wind velocity increased.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.671-680
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• 2007

The objective of this work is to reduce drag on a bluff body within a viscous flow by applying suction or injection of fluid along the surface of the body. In addition to minimizing drag, the optimal solution tends to reduce boundary layer separation and flow recirculation. When discretized by finite elements, the optimal control problem can be posed as a large-scale nonlinearly-constrained optimization problem. The constraints correspond to the discretized form of the Navier-Stokes equations. Unfortunately, solving such large-scale problems directly is essentially intractable. We developed several Sequential Quadratic Programming methods that are tailored to the structure of the control problem. Example problems of laminar flow around an infinite cylinder in two dimensions are solved to demonstrate the methodology. We use these optimal control techniques to study the influence of number of suction/injection holes and location of holes on the resulting optimized flow. We compare the proposed SQP methods against one another, as well as against available methods from the literature, from the point of view of efficiency and robustness. The most efficient of the proposed methods is two orders of magnitude faster than existing methods.

• Proceedings of the KIPE Conference
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• 1998.11a
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• pp.49-54
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• 1998

This paper describes a simulation 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 basic operation was analyzed in detail using equivalent circuits and the design of control system was developed using vector control method. A simulation model with EMTP code was conceived to evaluate the performance of the Unified power Flow Controller. The simulation results show that the developed simulation model is very effective to analyze the dynamic performance of the Unified Power Flow Controller.

• International Journal of Aerospace System Engineering
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• v.2 no.1
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• pp.6-11
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• 2015

An active flow control technique using blowing and distributed suction on low Reynolds airfoil is investigated. Simultaneous blowing and distributed suction can recirculate the jet flow mass, and reduce the penalty to propulsion system due to avoiding dumping the jet mass flow. Energy is injected into main flow by blowing on the suction surface, and the low energy boundary flow mass is removed by distributed suction, thus the flow separation can be successfully suppressed. Aerodynamic lift to drag ratio is improved significantly using the flow control technique, and the energy consumption is quite low.

• Smart Structures and Systems
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• v.2 no.1
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• pp.61-80
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• 2006

The concept of structural vibration control is to absorb vibration energy of the structure by introducing auxiliary devices. Various types of structural vibration control theories and devices have been recently developed and introduced into mechanical systems. One of such devices is damper employing controllable fluids such as ElectroRheological (ER) or MagnetoRheological (MR) fluids. MagnetoRheological (MR) materials are suspensions of fine magnetizable ferromagnetic particles in a non-magnetic medium exhibiting controllable rheological behaviour in the presence of an applied magnetic field. This paper presents the modelling of an MRfluid damper. The damper model is developed based on Newtonian shear flow and Bingham plastic shear flow models. The geometric parameters are varied to get the optimised damper characteristics. The numerical analysis is carried out to estimate the damping coefficient and damping force. The analytical results are compared with the experimental results. The results confirm that MR damper is one of the most promising new semi-active devices for structural vibration control.

• International Journal of Control, Automation, and Systems
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• v.3 no.spc2
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• pp.315-321
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• 2005

Interactions among multiple control functions of a UPFC installed in a power system have been observed in power system simulation and been reported in authors' previous publications [1,2]. This paper presents new analytical results about these observed interactions and concludes that they are due to the control conflict between the series and shunt part of the UPFC, which are connected through the internal common capacitor inside the UPFC. Investigation in the paper reveals, for the first time as far as the authors are aware of, that the linkage pattern of UPFC series and shunt part decides whether the control functions implemented by the UPFC series and shunt part conflict each other or not. This linkage pattern of UPFC series and shunt part can be described by the flow of active power through the UPFC at steady-state operation of the power system. Hence in order to predict the possible interactions among multiple control functions of the UPFC, an interaction indicator is proposed in the paper which is the direction and amount of active power flow through the internal link of the UPFC series and shunt part at steady-state operation of the power system. This proposed interaction indicator can be calculated from power system load flow solution without having to run simulation of the power system with UPFC controllers installed. By using the indicator, the interactions among multiple control functions of the UPFC caused by badly set controller's parameters are excluded. Therefore the indicator only identifies the possible existence of inherent control conflict of the UPFC.