New Power Control Approach to Improve the Power Quality of a Grid-Connected Wind Turbine

This paper aims to demonstrate the dynamic behavior of the wind turbine and the effectiveness of the control method used over a wide range of speed variations. The studied system consists of a three-blade turbine whose rotation axis is connected to that of the Doubly-Fed Induction Generator (DFIG) via a speed multiplier and a power electronics interface. The DFIG’s stator feeds directly into the stable grid, while its rotor is connected to the grid through a direct matrix frequency converter. The control of stator quantities is achieved by varying rotor quantities. The latters are governed by vector control with stator flux orientation. The optimal reference active power to be injected into the grid is determined by a program based on the perturb and observe (P&O) method. The stator reactive power and the reactive power at the converter input are forced to zero by the sliding mode control and the direct frequency converter, respectively. The advantage of this method is that the optimal power is calculated based on the available optimal torque. The latter is determined through an optimization program. In the literature, it is often found that optimal power is calculated by optimizing the rotational speed. However, in our work, the optimal power is calculated based on the optimal torque. This approach helps protect the machine against current overloads. The simulation results obtained in the MATLAB/Simulink environment demonstrate the proper functioning of the chosen system and the reliability of the developed control method.