• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.613-615
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• 2002

This paper deals with power factor of doubly fed induction generator for wind power generation in range of sub- and super-synchronous speed. To supply active and reactive power to grid. stator is connected to grid directly and rotor is connected to back-to-back PWM inverter for excitation. According to excitation level. DFIG could operate at the different mode. i.e., unity, leading, and lagging power factor.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1174-1175
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• 2008

A operation scheme to regulate the active power output of the hybrid system consisted of a doubly fed induction generator(DFIG) and a fuel-cell are presented. The power output of the wind turbine fluctuates as the wind speed varies and the slip power between the rotor circuit and power converter varies as the rotor speed change. A fuel cell system can be individually operated and adjusted output power. In this paper, a fuel-cell is performed to regulate the active output power in comparison with the active power output of a DFIG. Based on PSCAD/EMTDC power system tools, we simulated a DFIG and a fuel cell and investigated about dynamics of the output power in hybrid system.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.202-205
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• 2008

본 논문은 이중여자 발전기를 사용하는 풍력발전기에서 안정적인 계통투입을 위한 계통연계 전 후 발전기의 인덕턴스 변화에 따른 전류제어기 이득 값 선정에 대하여 연구하였다. DFIG(Doubly Fed Induction Generator)방식을 이용하는 풍력발전기는 회전자 전류제어를 함으로써 고정자의 전압을 제어하고, 제어된 고정자 전압은 계통과 연결된다. 특히 회전자 전류제어기 성능은 LVRT(Low Voltage Ride Through)등 예상하지 않은 외란에 대하여 빠른 응답성을 필요로 한다. 그러나 발전기가 계통과 연계되는 순간 발전기의 내부 파라미터 값의 변동이 발생하며, 이는 계통 투입 전 발전기 파라미터에 근거한 RSC(Rotor Side Converter)측 전류제어기 이득 값에 영향을 미쳐, 전류제어가 불안정하게 하는 원인이 되거나, 전류제어 응답성을 낮추게 하는 요인이 된다. 따라서, 본 연구에서는 계통투입 전 후의 RSC측 전류제어기의 이득 값을 달리하여 안정적인 계통 투입이 가능하도록 하는 알고리즘을 시뮬레이션과 실험으로 증명하였다.

• Journal of Power Electronics
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• v.19 no.2
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• pp.569-579
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• 2019

A robust controller is designed based on feedback linearization and sliding mode control to damp sub-synchronous control interaction (SSCI) in doubly fed induction generator (DFIG) wind power plants (WPPs) interfaced with the grid. A feedback-linearized sliding mode controller (FLSMC) is developed for the rotor-side converter (RSC) through feedback linearization, design of the sliding mode controller, and parameter tuning with the use of particle swarm optimization. A series-compensated 100-MW DFIG WPP is adopted in simulation to evaluate the effectiveness of the designed FLSMC at different compensation degrees and wind speeds. The performance of the designed controller in damping SSCI is compared with proportional-integral controller and conventional sub-synchronous resonance damping controller. Besides the better damping capability, the proposed FLSMC enhances robustness of the system under parameter variations.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1110-1122
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• 2018

This paper proposes an alternative method to evaluate the effect of wind power to the power system stability with small disturbance. Alternatively, available techniques for stability analysis of a power system based on deterministic methods are less accurate for high penetration of wind power. Numerical simulations of random behaviors are computationally expensive. A stochastic stability index (SSI) is proposed for the power system stability evaluation based on the theory of stochastic stability and energy function, specifically the stochastic derivative of the relative well-defined energy function and the critical energy. The SSI is implemented on the modified nine-bus system including wind turbines under different conditions. A doubly-fed induction generator (DFIG) wind turbine is characterized and modeled using measured wind data from several sites in Thailand. Each of the obtained wind power data is analyzed. The wind power effect is modeled considering the aggregated effect of wind turbines. With the proposed method, the system behavior is properly predicted and the stability is quantitatively evaluated with less computational effort compared with conventional numerical simulation methods.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.3
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• pp.531-538
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• 2009

The paper deals with an operation scheme to improve the forecasting of output range and to regulate the active power output of the hybrid system consisting of a doubly fed induction generator (DFIG) and a fuel-cell. The power output of the wind turbine fluctuates as the wind speed varies and the slip power between the rotor circuit and power converter varies as the rotor speed change. The power fluctuation of a DFIG makes its operation difficult when a DFIG is connected to grid. A fuel cell system can be individually operated and adjusted output power, hence the wind turbine and fuel cell hybrid system can overcome power fluctuation by using a fuel-cell power control. In this paper, a fuel-cell is performed to regulate the active power output in comparison with the regulated active power output of a DFIG. And it also improves the forecasting of output range. Based on PSCAD/EMTDC tools, a DFIG and a proton exchange membrane fuel cell(PEMFC) is simulated and the dynamics of the output power in hybrid system are investigated.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1116_1117
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• 2009

전력계통에서의 풍력 발전의 설치가 증가하면서 사고 발생시 전체 계통에 대한 신뢰도 및 안정도에 영향을 미친다. 이를 고려한 Fault Ride Through 제어 기법은 보다 안정적인 계통운영을 위한 방안이다. 최근 대부분의 풍력발전시스템은 이중여자 유도형 발전시스템(DFIG)이 설치되는데, 이는 전력변환장치를 이용한 유효 및 무효 전력 제어가 가능한 가변속 풍력발전시스템이다. 본 논문은 PSCAD/EMTDC를 통해 DFIG를 모델링하고 Crow Bar와 Rotor Side Converter의 연계 제어를 이용한 Fault Ride Through 제어 기법을 시뮬레이션 결과를 통해 확인 하였다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.93-94
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• 2011

This paper analyzes the shaft torsion of a doubly-fed induction generator (DFIG) for a wind farm collector system fault. When a fault occurs, the active power of the DFIG cannot be transmitted to the grid and thus accelerates the rotation of both the blade and the rotor. Due to the different inertia of these, the angle of deviation fluctuates and the shaft torsion is occurred. This becomes much severe when the rotational speed of the blade exceeds a threshold, which activating the pitch control to reduce the mechanical power. The torque, which can be sixty times larger than that in the steady state, may destroy the shaft. The shaft torsion phenomena are simulated using the EMTP-RV simulator. The results indicate that when a wind farm collector system fault occurs, a severe shaft torsion is occurred due to the activation of the pitch control.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1334-1339
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• 2016

In a power grid that has a high wind power penetration, the fast voltage support of a wind power plant (WPP) during the grid fault is required to stabilize the grid voltage. This paper proposes a voltage control scheme of a doubly-fed induction generator (DFIG)-based WPP that can promptly support the voltage of the point of common coupling (PCC) of a WPP during the grid fault. In the proposed scheme, the WPP and DFIG controllers operate in a voltage control mode. The DFIG controller employs two control loops: a maximum voltage dip-dependent reactive current injection loop and a reactive power to voltage loop. The former injects the reactive power in proportion to the maximum voltage dip; the latter injects the reactive power in proportion to the available reactive power capability of a DFIG. The former improves the performance of the conventional voltage control scheme, which uses the latter only, by increasing the reactive power as a function of the maximum voltage dip. The performance of the proposed scheme was investigated for a 100-MW WPP consisting of 20 units of a 5-MW DFIG under various grid fault scenarios using an EMTP-RV simulator. The simulation results indicate that the proposed scheme promptly supports the PCC voltage during the fault under various fault conditions by increasing the reactive current with the maximum voltage dip.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.827-834
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• 2014

In order to meet the low voltage ride-through requirement in a grid code, a wind power plant (WPP) has to stay connected to a grid, supporting the voltage recovery for a grid fault. To do this, a plant-level controller as well as a wind generator (WG) controller is essential. The dynamic response of a WPP should be analyzed in order to design a plant-level controller. The dynamic response of a WPP for a grid fault is the collective response of all WGs, which depends on the wind speed approaching the WG. Thus, the dynamic response of a WPP should be analyzed by taking the wake effect into consideration, because different wind speeds at WGs will result in different responses of the WPP. This paper analyzes the response of a doubly fed induction generator (DFIG)-based offshore WPP with a grid fault taking into account the wake effect. To obtain the approaching wind speed of a WG in a WPP, we considered the cumulative impact of multiple shadowing and the effect of the wind direction. The voltage, reactive power, and active power at the point of common coupling of a 100 MW DFIG-based offshore WPP were analyzed during and after a grid fault under various wind and fault conditions using an EMTP-RV simulator. The results clearly demonstrate that not considering the wake effect leads to significantly different results, particularly for the reactive power and active power, which could potentially lead to incorrect conclusions and / or control schemes for a WPP.