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This paper studied mathematical model of doubly-fed induction generator (DFIG) based wind turbine generation system under unbalanced voltage. A dual-PI current control strategy was proposed to improve the performance of DFIG's rotor side convert (RSC) under asymmetrical voltage condition. The symmetrical component theory is employed to decompose asymmetrical three-phase variable such as voltage and...
Doubly Fed Induction Generators (DFIG) has emerged as a suitable alternative for conversion of wind energy to grid quality energy under varying wind conditions. Often the control mechanism use large number of sensors and employ complex computations. Moreover, the reported control schemes for DFIG employing grid side converter (GSC) do not ensure a drawl of unity power factor (upf) sinusoidal current...
New regulatory requirements outlined in the European Grid Code dictate fault ride-through and reactive power support requirements for wind energy conversion systems. This paper introduces a simple emergency control scheme for DFIG-based wind turbines to comply with the grid code requirements. The proposed control design uses an enhanced phase locked loop (PLL) system to extract the synchronization...
This paper proposes a new vector-based hysteresis current regulator (VBHCR) in the rotor-side converter of DFIG to enhance the control performance under unbalanced supply voltage condition. The “Γ-form” is used for the equivalent circuit of the machine to reduce the modeling complexity. This is followed by presenting the principle and practical implementation of the proposed VBHCR in the DFIG application...
This paper presents a control method that reduces the pulsating torque and dc voltage problems of a Doubly Fed Induction Generator (DFIG)-based wind turbine system. To reduce the torque and the power ripple, a current control scheme, consisting of a proportional integral (PI) controller, is presented in a positive synchronously rotating reference frame and is capable of providing a precise current...
This paper proposes a ride-through technique of doubly-fed induction generator (DFIG) wind turbine systems. The control technique uses energy storage devices (ESD) which are controlled with current and power control loops. During grid faults, the generator output power can be reduced by increasing the generator speed, resulting in increased inertial energy of the rotational body. Also, the output...
This paper implements of a three phase grid synchronization for doubly-fed induction generators (DFIG) in wind generation system. A stator flux oriented vector is used to control the variable speed DFIG for the utility grid synchronization, active power and reactive power. Before synchronization, the stator voltage is adjusted equal to the amplitude of the grid voltage by controlling the d-axis rotor...
This paper presents the Direct model reference adaptive internal model controller for doubly fed induction generator used in wind farms based on MIT Rule adjustment mechanism with dither injection. Direct model reference adaptive internal model controller is developed and it is tuned using MIT rule. Rotor current controller is designed using direct model reference adaptive internal model controller...
Nowadays, there is a tendency to increase the power of wind turbines. Multilevel converter is a realistic alternative in such high power applications. As the most widely used variably speed wind turbine, doubly fed induction generators (DFIG) are very sensitive to grid disturbances. Moreover, grid codes have been revised to require wind turbines to provide Low Voltage Ride-Through (LVRT) ability....
In this work a new strategy for controlling doubly-fed induction generator is presented. The proposed scheme has two nested control loops. The internal loop regulates the rotor flux, in opposition to the classical approach of controlling the rotor currents. The external loop controls stator currents. Since the machine is connected directly to the grid, this results in a direct control of active and...
This paper investigates an improved control and operation of a DFIG system under unbalanced network conditions. A new rotor current control strategy is presented, which consists of a main controller and an auxiliary compensator. The main controller is constructed in the same way as the conventional vector control design without involving sequential-component separation in order to guarantee system...
This paper presents the direct model reference adaptive internal model controller for doubly fed induction generator used in wind farms based on MIT rule adjustment mechanism in addition to Perrin equation adjustment mechanisms with improved internal model controller filter design. Direct model reference adaptive internal model controller is developed and it is tuned using MIT rule adjustment mechanism...
Based on feedback of the stator current phase, a new control strategy of doubly-fed induction generator (DFIG) is proposed. Under the condition that stator current amplitude maintains at rated value, the required rotor control voltage is directly calculated by the stator flux, rotor rotating speed, stator current phase and its corresponding error. Constant converter switching frequency and stator...
The doubly fed induction generator is particularly appropriate to be used in wind power generation systems. However, in weak grids its stator connection to unbalanced or distorted voltages imposes low frequency and high amplitude rotor current harmonics. Also, the grid side converter must deal with the same voltage conditions. The paper addresses the first issue presenting a voltage harmonics controller...
Summary form only given. This work demonstrates that the integration of variable speed wind systems with doubly fed induction generators and a four quadrant AC-to-AC converter connected to the rotor windings (DFIG), increases the transient stability margin of the electrical grids, when compared with the case where the fixed speed wind systems with cage generators are used. The results clearly show...
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