• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.197-198
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• 2015

As the global to increase the wind power penetration in the power system, grid-integration standards have been proposed for the stable integration of the large-scale wind farm. Particularly, the low voltage ride through function has been emphasized, as it relates to the voltage and reactive power control of the wind turbine and the rest generators. This paper proposes the non-wind power generator control method in order to improve the wind power penetration. To prove the effectiveness of the proposed strategy, the simulation study is implemented in the Jeju power system. It can improve the wind power penetration by the effective control of the control generators.

• Journal of IKEEE
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• v.21 no.1
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• pp.81-84
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• 2017

As the demands for offshore wind power generation systems on a large scale have grown dramatically, and extensive developments in PMSG (Permanent Magnet Synchronous Generator) and DFIG (Doubly-fed Induction Generator) wind turbine system have been going on. However, the wind power systems have been more sophisticated, and their reliability becomes critical issues. Averagely, wind turbines have shut down for about a week per year for repairs and maintenance. Especially the high speed gearbox of DFIG is inevitable components for high power generation, but becomes one of the critical failures. In this paper, a new reliable gearless wind turbine structure is proposed. The gearless wind turbine can operate on a maximum power points by controlling the speed of a rotational stator. The proposed approach is verified by PSIM simulations, resulting in increased energy reliability.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1232-1233
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• 2007

As the number of wind turbines installed increase, the power from wind energy starts to replace conventional generation units and its influence on power system can not be neglected. Because of the intermittent nature of wind resource, the output power of wind turbine fluctuates according to wind speed variation. In this point of view, it is necessary for wind turbines to be equipped with power regulation ability. The doubly fed induction generator (DFIG) is one of the main techniques used in variable speed wind turbines. This thesis focuses on the development of modified control scheme of DFIG to regulate output power. The proposed control scheme achieves active power output regulation so as to stabilize the power system.

• Journal of Power Electronics
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• v.16 no.2
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• pp.675-684
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• 2016

This paper presents a new stand-alone wind-based induction generator system with constant frequency and adjustable output voltage. The proposed generator consists of a six-phase cage-rotor induction machine with two separate three-phase balanced stator windings and a three-phase space vector pulse width modulation inverter that operates as a static synchronous compensator (STATCOM). The first stator winding is fed by the STATCOM and used to excite the machine while the second stator winding is connected to the generator external load. The main frequency of the STATCOM is determined to be constant and equal to the load-requested frequency. The generator output frequency is independent of the load power demand and its prime mover speed because the frequency of the induced emf in the second stator winding is the same as this constant frequency. A sliding mode control (SMC) is developed to regulate the generator output voltage. A second SMC is used to force the zero active power exchanged between the machine and the STATCOM. Some simulation and experimental results are presented to prove the validity and effectiveness of the proposed generator system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.4
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• pp.48-56
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• 2012

The object of this paper is the controller for supplying stably power in a separate house in which a hybrid electrical storage system with a stand-alone photovoltaic/wind power generation system and a small generator is applied. In the photovoltaic/wind hybrid power system used in the separate house, when only the battery is used in sunless days, the capacity of the battery is become larger. In particular, as in recent days, if cloudy days are frequent due to anomaly climate, it is difficult to estimate the number of sunless days. Accordingly, it is preferable to build the electrical storage system that numbers of sunshineless days are to be controlled and a shortage amount of the power generation capacity is to be handled by a small generator system. In order to supply stably power of new renewable energy such as solar to any separate houses, it is preferable to reduce the capacity of battery by decreasing the number of sunless days when estimating the capacity of battery and to drive the small generator for compensation of the power shortage. Such system needs components including inverters for photovoltaic and wind power generation system, batteries and controllers for automatically driving the small generator, based upon the nature of the stand-alone house, and it is preferable to use the controller having a simpler and higher stability by adopting the all-in-one scheme to facilitate its maintenance.

• Journal of Power Electronics
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• v.4 no.4
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• pp.205-216
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• 2004

In this paper, a three-phase induction machine-based wind power generation scheme is proposed. This scheme uses a low-cost diode bridge rectifier circuit connected to an induction machine via an ac load voltage regulator (AC-LVR) to regulate dc power transfer. The AC-LVR is used to regulate the DC load voltage of the diode bridge rectifier circuit which is connected to the three-phase self-excited induction generator (SEIG). The excitation of the three-phase SEIG is supplied by the static VAR compensator (SVC). This simple method for obtaining a full variable-speed wind turbine system by applying a back-to-back power converter to a wound rotor induction generator is useful for wind power generation at widely varying speeds. The dynamic performance responses and the experimental results of connecting a 5kW 220V three-phase SEIG directly to a diode bridge rectifier are presented for various loads. Moreover, the steady-state simulated and experimental results of the PI closed-loop feedback voltage regulation scheme prove the practical effectiveness of these simple methods for use with a wind turbine system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.923-933
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• 2016

This paper proposes a new method for evaluating Effective Load Carrying Capability(ELCC) and capacity credit(C.C.) of power system including Wind Turbine Generator(WTG) combined with Battery Energy Storage System(BESS). WTG can only generate electricity power when the fuel(wind) is available. Because of fluctuation of wind speed, WTG generates intermittent power. In view point of reliability of power system, intermittent power of WTG is similar with probabilistic characteristics based on power on-off due to mechanical availability of conventional generator. Therefore, high penetration of WTG will occur difficulties in power operation. The high penetration of numerous and large capacity WTG can make risk to power system adequacy, quality and stability. Therefore, the penetration of WTG is limited in the world. In recent, it is expected that BESS installed at wind farms may smooth the wind power fluctuation. This study develops a new method to assess how much is penetration of WTG able to extended when Wind Turbine Generator(WTG) is combined with Battery Energy Storage System(BESS). In this paper, the assessment equation of capacity credit of WTG combined with BESS is formulated newly. The simulation program, is called GNRL_ESS, is developed in this study. This paper demonstrates a various case studies of ELCC and capacity credit(C.C.) of power system containing WTG combined with BESS using model system as similar as Jeju island power system. The case studies demonstrate that not only reasonable BESS capacity for a WTG but also permissible penetration percent of WTG combined with BESS and reasonable WTG capacity for a BESS can be decided.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.215-221
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• 2014

To satisfy the high voltage direct current (HVDC) grid connection demand for wind power generation system, a novel topology and control strategy of HVDC grid connection for open-winding permanent magnet synchronous generator (PMSG) based wind power generation system is proposed, in which two generator-side converter and two isolated DC/DC converters are used to transmit the wind energy captured by open winding PMSG to HVDC grid. By deducing the mathematic model of open winding PMSG, the vector control technique, position sensorless operation, and space vector modulation strategy is applied to implement the stable generation operation of PMSG. Finally, the simulation model based on MATLAB is built to validate the availability of the proposed control strategy.

• Journal of Electrical Engineering and Technology
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• v.5 no.1
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• pp.61-69
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• 2010

This paper presents a study of a DFIG wind power generation system for real-time simulations. For real-time simulations, the Real-Time Digital Simulator (RTDS) and its user friendly interface simulation software RSCAD are used. A 2.2MW grid-connected variable speed DFIG wind power generation system is modeled and analyzed in this study. The stator-flux oriented vector control scheme is applied to the stator/rotor side converter control, and the back-to-back PWM converters are implemented for the decoupled control. The real-wind speed signal extracted by an anemometer is used for a realistic, reliable and accurate simulation analysis. Block diagrams, a mathematical presentation of the DFIG and a control scheme of the stator/rotor-side are introduced. Real-time simulation cases are carried out and analyzed for the validity of this work.

• Journal of Magnetics
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• v.16 no.4
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• pp.374-378
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• 2011

Axial Field Permanent Magnet (AFPM) generators are widely applied for the small wind turbine because of the higher power density per unit weight than that of the conventional radial field generator. It is caused by the disc shaped rotor and the stator structures. The generally used AFPM generator, AFER-NS generator, is composed of the two side's external rotors and non-slotted stator without stator core. However, the output voltage and the output power are limited by the large reluctance by the long air-gap flux paths. In this paper, the design study of AFIR-S generator having double side's slotted stator core is accomplished to improve the output generation characteristics. The electromagnetic design analysis and the design improvement of the suggested AFIR-S generator are studied. Firstly, the electromagnetic design analysis was done to increase the power density. Secondly, the design optimizations of the rotor pole-arc ratio of permanent magnet are accomplished to increase the output power and to reduce the cogging torque. Finally, the output performances of AFER-NS and AFIR-S generator are compared with each other. For this study, 3D FEA is applied for the design analysis because of three dimensional electromagnetic structures.