Contribution of Variable Speed Wind Turbine Generator based on DFIG using ADRC and RST Controllers to Frequency Regulation

Abstract

In the interconnected power systems, there must always be a balance between the amount of electricity produced and the amount of electricity consumed in order to keep the grid frequency stable and nearby to its nominal value. Therefore, any change in consumption can lead to imbalance, instability, load shedding and system frequency disturbances. With the increase of wind energy penetration level in the electrical network, it has become necessary to make wind generators participate in frequency regulation. The fundamental objective of this research paper is to investigate the ability of wind turbine at variable speed equipped with doubly fed induction generator (DFIG) to contribute in the grid frequency regulation. For the purpose of the contribution in the frequency regulation, the wind turbine system must inject a supplementary power support into the electrical network. To do that, two control strategies are adopted: the first one is the synthetic inertia control which uses the kinetic energy reserved and stocked in the turbine and generator rotors of the wind system. The second one is the droop frequency control which includes the deloading method that allows to the VSWT to create a certain reserve active power. Then, each of these control techniques is implemented and their performances are evaluated in case of frequency variation. Moreover, the control structure that uses the combination of these two techniques is also implemented and studied. The active disturbance rejection control strategy (ADRC), the classical PI controller and the polynomial RST controller have been adopted to command the rotor side converter (RSC) of the DFIG which allows it to provide, in case of frequency fault, a support for the power system into the grid by adjusting the rotor speed. The performance of these controllers are tested and compared and the simulation is performed by MATLAB/Simulink simulation software.