• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.399-405
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• 2014

For stable integration of large-scale wind farms, integration standards (Grid codes) have been proposed by the system operator. In particular, voltage control of large-scale wind farms is gradually becoming important because of the increasing size of individual wind farms. Among the various voltage control methods, Secondary Voltage Control (SVC) is a method that can control the reactive power reserve of a control area uniformly. This paper proposes hybrid SVC when a large-scale wind farm is integrated into the power grid. Using SVC, the burden of a wind turbine converter for generating reactive power can be reduced. To prove the effectiveness of the proposed strategy, a simulation study is carried out for the Jeju system. The proposed strategy can improve the voltage conditions and reactive power reserve with this hybrid SVC.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.47-48
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• 2016

Parallel distributed generators (DGs) in the islanded micro-grid are normally controlled with the aid of the droop control scheme. However, the traditional droop control methods which use the P-${\omega}$ and Q-E curve to share power between DGs are still concerned to improve the accurate of reactive power sharing and variation of frequency and voltage at the point of common coupling (PCC). This paper proposes a control scheme to solve the limitation of microgrid in islanded operation such as reactive power sharing accuracy and PCC voltage and frequency restoring. In order to achieve the control objective, a secondary control is implemented with both central controller and local controller by using the low bandwidth communications. The effectiveness of the proposed control scheme is analyzed through the simulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1540-1548
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• 2010

KEPCO proposes enhanced voltage management system that is a coordinate voltage control system between the hierarchical voltage control system and the slow voltage control system. It has been installing in Jeju island. VMS consists of a master controller, CVC (Continuous Voltage Controller) and DVC (Discrete Voltage Controller). CVC consists of main controller, FDMU (Field Data Measurement Unit) and several RPDs (Reactive Power Dispatcher). CVC has a control scheme with AVRs of generator to maintain the voltage of a pilot bus in a power system, DVC has a control scheme with static reactive power sources, like a shunt capacitor, a shunt reactor, ULTC and so on, to maintain the reactive power reserve of a power system and a master controller is executed to recover reactive power margin of a power system through coordinated control between CVC and DVC.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.213-214
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• 2014

This paper compares two instantaneous reactive power definitions in DFIG wind turbine with a back-to-back three-level neutral-point clamped voltage source converter under unbalanced grid conditions. In general, conventional definition of instantaneous reactive power is obtained by taking an imaginary component of complex power. The other definition of instantaneous reactive power can be developed based on a set of voltages lagging the grid input voltages by 90 degree. A complex quantity referred as a quadrature complex power is defined. Proposed definition of instantaneous reactive power is derived by taking a real component of quadrature complex power. The characteristics of two instantaneous reactive power definitions are compared using the ripple-free stator active power control algorithm in DFIG. Instantaneous reactive power definition based on quadrature complex power has a simpler current reference calculation control block. Ripple of instantaneous active and reactive power has the same magnitude unlike in conventional definition under grid unbalance. Comparison results of two instantaneous reactive power definitions are verified through simulation.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.654-664
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• 2017

This paper proposed an unified dual-phase-shift (UDPS) control for dual active bridge (DAB) converters in order to improve efficiency for a wide output power range. Different operating modes of UDPS are characterized with respect to the reactive current distribution. The proposed UDPS has the same output power capability with conventional phase-shift (CPS) method. Furthermore, its implementation is simple since only the change of the leading phase-shift direction is required for different operating power range. The proposed UDPS control can minimize both the inductor rms current and the circulating reactive current for various voltage conversion ratios and load conditions. The optimal phase-shift pairs for two bridges of DAB converter are derived with respect to the comprehensive reactive power loss model, including the reactive components delivered from the load and back to the source. Simulation and experimental results are illustrated and explained with details. The effectiveness of the proposed method is verified in terms of reactive power losses minimization and efficiency improvement.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.181-183
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• 2008

This paper suggests local voltage control method to achieve coordinative control between STATCOM and other reactive power resources, such as Shunt Capacitor/Reactors and OLTC. Voltage/Reactive power control has various difficult aspects to control because of analysis and system dynamics error. This control method suggests practical algorithm regarding system voltage and reactive power status which is easy to implement in substation basis. In normal status, STATCOM-Shunts-OOTC are in operation. In emergency status, OLTC is locked. This algorithm is tested and verified in EMTDC.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.2
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• pp.107-115
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• 2006

In this paper, a new speed sensorless control based on an instantaneous reactive power is proposed for the interior permanent magnet synchronous motor(IPMSM) drives. In proposed algorithm, the current observer estimates the line currents and the estimated speed can be yielded from the voltage equation because the information of speed is included in back EMF. To implement speed sensorless control, the current observer is composed by using the voltage equation of the IPMSM in the stationary reference frame fixed to the stator. The estimated speed of the rotor is composed by using the voltage equation of the IPMSM in the rotating reference frame fixed to the rotor The estimated speeds to minimize the speed error compensated by using the instantaneous reactive power. The instantaneous reactive power is calculated on the rotating reference frame fixed to the rotor. The effectiveness of the preposed algorithm is confirmed by the experiments.

• Journal of the Semiconductor & Display Technology
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• v.10 no.2
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• pp.83-89
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• 2011

In this study, we investigated the effects of shutter control by Reactive Magnetron Sputtering using Inductively-Coupled Plasma(ICP) for obtaining ZnO thin films with high purity. The surface morphologies and structure of deposited ZnO thin films were characterized using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Diffractometer (XRD). Also, optical and chemical properties of ZnO thin films were analyzed by Spectroscopic Ellipsometer (SE) and X-ray Photoelectron spectroscopy (XPS). As a result, it observed that ZnO thin films grown at reactive sputtering using shutter control and ICP were higher density, lower surface roughness, better crystallinity than other conventional sputtering deposition methods. For obtaining better quality deposition ZnO thin films, we will investigate the effects of substrate temperature and RF power on shutter control by a reactive magnetron sputtering using inductively-coupled plasma.

• Journal of Korean Physical Therapy Science
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• v.13 no.1
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• pp.75-82
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• 2006

Purpose: The purpose of this experimental study have been testifying about reactive muscle control regarding sternocleidomastoid and psoas. Low back pain patient do not sit-up exercise without abnormality of trunk flexor. The reason of problem is unbalance sternocleidomastoid and psoas. According to George J, Goodheart who have been developing Applied Kinesiology (A. K.) since reactive muscle recognized gait testing in 1964. Materials and Methods: From September, 2004 to February, 2005, I have controled sternocleidomastoid and psoas. It is applied to the patients who are unable sit up exercise at Yang-Dong local clinic, Yang-Pyung county, Kyung-Gi Do province in Korea. 24 Patients divided 2 groups. A group is applied general physical therapy. Also B group is added reactive muscle control from M.E.M.P.T.(Korean society of muscle and energy monitoring physical therapy) Results : The results of this study follow. 1. Possible sit up group 8 persons of the second group. 2. Not possible sit up group the others. Conclusion: The study present that reactive muscle control sternocliedomastoid and psoas is useful in patient with low back pain is difficult to sit up.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1189-1191
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• 1999

This paper deals with the real and reactive power control of BESS(Battery Energy H Storage System) interconnected to power system. The real and reactive power control of proposed customer side BESS are performed by controlling the amplitude and the phase of inverter output voltage via power flow equation. Also in order to control the amplitude and phase of output voltage of proposed BESS, single-pulse width control method is used. The BESS and controller is implemented and the active and reactive power control is simulated by using the PSCAD/EMTDC simulation program.