• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2268-2277
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• 2017

As constantly increasing wind power penetrates power grid, wind power plants (WPPs) are exerting a direct influence on the traditional power system. Most of WPPs are using variable speed constant frequency (VSCF) wind turbines equipped with doubly fed induction generators (DFIGs) due to their high efficiency over other wind turbine generators (WTGs). Therefore, the analysis of DFIG has attracted considerable attention. Precisely measuring optimum reference speed is basis of utilized maximum wind power in electric power generation. If the measurement of wind speed can be easily taken, the reference of rotation speed can be easily calculated by known system's parameters. However, considering the varying wind speed at different locations of blade, the turbulence and tower shadow also increase the difficulty of its measurement. The aim of this study is to design fuzzy controllers to replace the wind speedometer to track the optimum generator speed based on the errors of generator output power and rotation speed in varying wind speed. Besides, this paper proposes the fuzzy adaptive PID control to replace traditional PID control under rated wind speed in variable-pitch wind turbine, which can detect and analyze important aspects, such as unforeseeable conditions, parameters delay and interference in the control process, and conducts online optimal adjustment of PID parameters to fulfill the requirement of variable pitch control system.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.326-328
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• 2008

본 논문의 목표는 실제 시스템과 가장 유사한 이중여자 유도발전기(Doubly-Fed Induction Generator)의 시뮬레이터를 구현하고 실험을 통해서 그것을 검증하는 것이다. 바람의 속도를 2D 룩업 테이블을 이용하여 데이터화 한 후 터빈 모델의 입력으로 인가한다. 터빈 모델의 파라미터는 실험용 이중여자 유도발전기의 것과 동일하게 설정하여 실제 시스템과 유사하게 하였다. 지금까지는 이중여자 유도발전기를 모사하기 위하여 매트랩(Matlab) 등을 이용하였지만 실제와 다소 다르다는 문제와 구현하기 힘들다는 문제를 가지고 있었다. 하지만 본 논문에서는 심플로러(Simplorer)를 이용하여 쉽고 정확한 시뮬레이터를 구현하였다. 터빈과 이중여자 유도발전기는 기어를 이용하여 직결함으로써 실제 시스템과 매우 가깝게 모사하였으며 이중여자 유도발전기의 회전자를 여자시키기 위해 이산 캐리어 변조 방법을 이용하여 매트릭스 컨버터를 구동하였다. 그리고 실험을 통해서 시뮬레이터의 결과와 실험 결과의 비교 및 검증을 한다. 궁극적으로 어떤 지역의 바람의 품질과 발전량 등 중요한 정보를 얻기 위해 실제 크기의 발전기를 설치하지 않고 본 논문에서 개발한 시뮬레이터를 이용하여 쉽게 그 정보들을 얻을 수 있다.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.91-103
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• 2015

This paper investigates control algorithms for a doubly fed induction generator with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage wind power system under unbalanced grid conditions. Negative sequence control algorithms to compensate for unbalanced conditions have been investigated with respect to four performance factors: fault ride-through capability, instantaneous active power pulsation, harmonic distortions, and torque pulsation. The control algorithm having zero amplitude of torque ripple indicates the most cost-effective performance in terms of torque pulsation. The least active power pulsation is produced by a control algorithm that nullifies the oscillating component of the instantaneous stator active and reactive power. A combination of these two control algorithms depending on operating requirements and depth of grid unbalance presents the most optimized performance factors under generalized unbalanced operating conditions, leading to a high-performance DFIG wind turbine system with unbalanced grid adaptive features.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1172-1173
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• 2008

At the moment, the control ability of wind farms is a prime research concern for the grid integration of large wind farms, due to their required active role in the power system. As more wind turbines are installed, the power from wind energy will start to replace conventional generation units and its influence on power systems cannot be neglected. Besides, because of the intermittent nature of wind the output power of wind turbines fluctuates according to wind speed variation. Especially an isolated power system with small capacity such like Jeju needs more systematic solutions and regulations(grid code). This paper presents the idea of approach for centralized operating wind farm strategy to regulate the wind farm power production to the reference power ordered by the system operator. The doubly fed induction generator(DFIG) can control active and reactive power in feasible range. So wind farm comprised of DFIG has the possibility of a controllable component in the power system. The presented wind farm control has a hierarchical structure with both a wind farm control level and a wind turbine control level.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.532-540
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• 2014

It is necessary to measure the current of rotor for controlling the active and reactive power generated by the stator side of the doubly fed induction generator (DFIG) system. There are offset and scaling errors in the current measurement. The offset and scaling errors cause one and two times current ripples of slip frequency in the synchronous reference frame of vector control, respectively. This paper proposes a compensation method to reduce their ripples. The stator current is variable according to the wind force but the rotor current is almost constant. Therefore input of the rotor current is more useful for a compensation method. The proposed method adopts the synchronous d-axis current of the rotor as the input signal for compensation. The ripples of the measurement errors can be calculated by integrating the synchronous d-axis stator current. The calculated errors are added to the reference current of rotor as input of the current regulator, then the ripples are reduced. Experimental results show the effectiveness of the proposed method.

• Journal of Power Electronics
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• v.13 no.6
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• pp.1032-1041
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• 2013

This paper investigates control algorithms for a doubly fed induction generator with a back-to-back three-level neutral-point clamped voltage source converter in medium voltage wind power systems under unbalanced grid conditions. Three different control algorithms to compensate for unbalanced conditions have been investigated with respect to four performance factors; fault ride-through capability, instantaneous active power pulsation, harmonic distortions and torque pulsation. The control algorithm having a zero amplitude of torque ripple shows the most cost-effective performance concerning torque pulsation. The least active power pulsation is produced by the control algorithm that nullifies the oscillating component of the instantaneous stator active and reactive powers. A combination of these two control algorithms depending on the operating requirements and the depth of the grid unbalance presents the most optimized performance factors under generalized unbalanced operating conditions leading to high performance DFIG wind turbine systems.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.431-433
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• 2008

본 논문은 댐핑 저항을 사용하지 않고 LCL필터를 사용한 계통 연계형 PWM 컨버터를 제어하기 위해 종속(cascade) 구조를 갖는 궤환선형화 제어기법을 제안한다. 제안된 제어 알고리즘은 2[MW] DFIG 풍력발전 시스템에 적용한 시뮬레이션과 3[kW] AC/DC PWM 컨버터에 적용한 실험을 통해 그 타당성이 검증된다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1182-1183
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• 2008

In this paper, we develop PCS for doubly-fed induction-type wind generator(DFIG). PCS consists of a converter set and a controller. PCS controls the active power of wind generator and the reactive power of wind turbine system according to rotating speed, instantaneous power, grid quality, and order by transmission system operator.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.274-276
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• 2006

본 논문은 계통전압 불평형시 풍력발전용 DFIG (Doubly-Fed Induction Generator)의 유효전력과 무효전력 맥동을 제어하는 새로운 기법을 제시한다. 발전기 토크식을 대칭좌표법을 이용하여 정상분과 역상분의 전류로 표현하고 토크 맥동을 제거하기 위한 회전자 역상분의 지령전류를 유도한다. PSCAD/EMDTC를 이용한 시뮬레이션을 통해 제안한 방법의 타당성을 검증한다.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.60-64
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• 2003

신재생에너지 개발을 위한 권선형유도발전기의 유효전력제어와 무효전력제어에 대해 고찰하였다. 10kW DFIG에 양방향 AC/DC/AC 전력변환장치를 적용한 실험을 통해 유효전력제어와 무효전력제어를 검증하였고, 운전 개시 속도를 결정하는 방법과 전력변환장치 용량을 고려한 제어방법, 그리고 역률 가변을 통해 저속도 영역에서의 에너지 회수방안에 대해 고찰하였다.