PERFORMANCES OF DIRECT REACTIVE POWER CONTROL TECHNIQUE APPLIED TO THREE LEVEL-INVERTER UNDER RANDOM BEHAVIOR OF WIND SPEED

摘要

A doubly fed induction generator (DFIG) driven by a variable speed wind turbine (WT) is presented in this paper. The DFIG is supplied via a three-level inverter in its rotor, and controlled with a flexible algorithm based on fuzzy logic control (FLC) combined with the direct torque (DTC), getting the direct reactive power control (DRPC) technique, thereby enjoying the benefits of both at same time. The aim of this contribution is to analyze the performances and robustness of the proposed control technique, which is applied to a three-level inverter. Indeed, the main objectives are to obtain at the generator output (AC) sine waveforms signals with a low total harmonic distortion (THD), as well as minimum output voltages ripples, regardless of the variation of the wind speed, as well as, the possibility of energy management, the active and reactive powers control by the DFIG, and the usefulness of this machine as a local reactive power compensator. Some constraints are taken in to account to reflect the real operation of a wind driven, such as the randomness behavior of the wind speed allowing the three operation modes of the DFIG, i.e. sub, super and synchronous. Such operation is carried out with a successive and continuous manner, with a particular focus on synchronous and overspeed modes. The captured wind power is optimized to extract the maximum power using the appropriate maximum power point tracking (MPPT) algorithm, below a nominal turbine speed. We will be acting on the pitch angle control, beyond the nominal turbine speed, whereas the power extraction maximization amounts to regulate the power produced at its rate value. The simulation tests are performed under Matlab/Simulink and the results show the effectiveness of the control strategy that leads to better performances of the system.