Study on Direct Rotor Speed Predictive Hierarchical Strategy with Target-error Compensation for Double-controlled DFIG

The Doubly fed induction generator (DFIG) has an intricate control structure and poor transient performance under the cascaded double-loop control strategy. This article proposes a direct rotor speed prediction hierarchical strategy with target-error compensation for double-controlled DFIG to improve its transient and steady-state performance and reduce target-error. First, a direct rotor speed prediction strategy is designed to enhance system transient performance by establishing a direct correlation between rotor speed and rotor q-axis voltage. Continuous control set model predictive control (CCS-MPC) scheme combines vector modulation to obtain voltage vectors continuously and accurately. Second, a hierarchical method is that consists of rotor speed level prediction and current prediction is designed by introducing rotor speed error coefficient for rotor speed cost function to improve current steady-state performance and restrict rotor speed within an acceptable error range. And the optimal error coefficient is evaluated and selected. Third, a target-error compensation method is designed to improve rotor speed tracking performance by adding target-error term to the cost function of rotor speed. Finally, experimental results verify the effectiveness of the proposed strategy.