• Journal of Power Electronics
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• v.9 no.5
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• pp.781-790
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• 2009

This paper presents an implementation of a direct active and reactive power control for a doubly fed induction generator (DFIG), which is applied to a wind generation system as an alternative to the classical field-oriented control (FOC). The FOC has a complex control structure that consists of a current controller, a power controller and frame transformations. The performance of the FOC depends highly on parameter variations of the rotor and stator resistances and the inductances. The proposed direct power control (DPC) method produces a fast and robust power response without the need of complex structure and algorithms. One drawback, however, is its high power ripple during a steady state. In this paper, active and reactive power controllers and space-vector modulation (SVM) are combined to replace hysteresis controllers used in the original DPC drive, resulting in a fixed switching frequency of the power converter. Simulation results with the FOC and DPC for a 3kW DFIG are given and discussed, and the experimental results of a test involving identical machines are presented to illustrate the feasibility of the proposed control strategy.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.194-195
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• 2010

This paper investigates control algorithms for a doubly fed induction generator (DFIG) with back-to-back converter in medium-voltage wind power system under unbalanced grid conditions. Operation of DFIG under unbalanced grid conditions causes several problems such as overcurrent, unbalanced currents, active power pulsation and torque pulsation. Three different control algorithms to compensate for the unbalanced conditions have been investigated with respect to four performance factors; fault ride-through capability, efficiency, harmonic distortions and torque pulsation. The control algorithm having zero amplitude of negative sequence current shows the most cost-effective performance concerning fault ride-through capability and efficiency. The control algorithm for nullifying the oscillating component of the instantaneous active power generates least harmonic distortions. Combination of these two control algorithms depending on the operating requirements presents most optimized performance factors under the generalized unbalanced operating conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.3
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• pp.93-100
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• 1999

Wide operating range and speed control is needed for wind power generating and a Doubly Fed Induction Generator(DFlG) has good adaptivity for that purpose. Ths paper investigates speed and output stator power control using a grid connected to a DFlG in super-synchronous speed regions, by control of both magnitude and frequency of the voltage fed to the rotor. For the speed control analysis, torque simulation is perforrred whereby the different slip between qJernting rmtor driving frequency and synchronous frequency of M-G system awlied. To keep the output rating of the generator, the exciting frequency and voltage attenuation are arolied.rolied.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.83-84
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• 2011

This paper presents an analysis and a novel strategy for a doubly fed induction generator (DFIG) based wind energy conversion system under unbalanced grid voltage and non-linear load conditions. A proportional-resonant (PR) current controller is applied in both grid side converter (GSC) and rotor side converter (RSC). The RSC is controlled to mitigate the stator active power and the rotor current oscillations at double supply frequency under unbalanced grid voltage while the GSC is controlled to mitigate ripples in the dc-link voltage and compensate harmonic components of the network current. Simulation results using Psim simulation program are presented for a 2 MW DFIG to confirm the effectiveness of the proposed control strategy.

• 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.

• 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.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.969-971
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• 2000

This paper deals with characteristics analysis of Doubly-Fed Induction Generator (DFIG) in the supersynchronous speed regions. by control of voltage fed to the rotor using for bidirection control. This rotor voltage is controlled by con troll of inverter switching frequency and fire angle. Characteristics of DFIG is analyzed by steady-state algebraic equations of the equivalent circuit using numerical analysis. And it is compared with results of experiment. Consequently, this paper presented to find the optimal magnitude of voltage fed to the rotor for maximum power and PF, using result of characteristics analysis.

• Journal of Power Electronics
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• v.10 no.2
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• pp.194-202
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• 2010

The main cause of degradation in an unbalanced stand-alone doubly-fed induction generator (DFIG) system is negative sequence components that exist in the generated stator voltages. To eliminate these components, a hybrid current controller composed of a proportional-integral controller and a resonant regulator is developed in this paper. The proposed controller is applied to the rotor-side converter of a DFIG system for the purpose of compensating the negative stator voltage sequences. The proposed current controller is implemented in a single positive rotating reference frame and therefore the controller can directly regulate both the positive and negative sequence components without the need for sequential decomposition of the measured rotor currents. In terms of compensation capability and accuracy, simulations and experimental results demonstrated the excellent performance of the proposed control method when compared to conventional vector control schemes.

• Journal of the Korean Solar Energy Society
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• v.32 no.3
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• pp.19-25
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• 2012

About supply and demand to see that you need to match, the limitations of wind power capacity is low demand and the commitment of the general generator will exist between the minimum generation. if the turbine's output can be controlled, The limitation of wind power capacity will be adopted based on instant power generation. Namely, The minimum limits of wind power generation based load operation by calculating the amount that is higher than if the output should be restricted to highest operation. in this paper, we committed to the demand for low enough that the combination of the general generator of wind power capacity to accommodate the operation of determining whether the limit is intended to. For this, power system analysis program PSS/E was used, Jeju system by implementing the model simulations were performed.

• Journal of Power Electronics
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• v.10 no.1
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• pp.72-78
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• 2010

In this paper the operation of a double-fed wound-rotor induction machine, coupled to a wind turbine, as a generator at sub-synchronous speeds is investigated. A novel approach is used in the analysis, namely, the rotor power flow approach. The conditions necessary for operating the machine as a double-fed induction generator (DFIG) are deduced. Formulae describing the factors affecting the range of sub-synchronous speeds within which generation occurs are deduced. The variations in the magnitude and phase angle of the voltage injected to the rotor circuit as the speed of the machine changes to achieve generation at the widest possible sub-synchronous speed range is presented. Also, the effect of the rotor parameters on the generation range is presented. The analysis proved that the generation range could increase from sub-synchronous to super-synchronous speeds, which increases the amount of energy captured by the wind energy conversion system (WECS) as result of utilizing the power available in the wind at low wind speeds.