Adaptation Control For Grid Connection Of Double-Fed Variable-Speed Constant Frequency Wind Power Systems

Wind power generation is an effective way to solve the world energy crisis,and grid wind power is the most economical way for large-scale use of wind energy. Moreover, control strategy is one of the key techniques to utilize wind resources and improve power quality. Therefore, modeling and control for the entire wind power grid-connection systems are current research trend of wind power generation system. To this end, in this paper, modeling and control are investigated for variable-speed constant-frequency (VSCF) doubly fed induction generator (DFIG)-based wind power generation systems in grid connected operation. And the main results are as follows:The control strategy is investigated for VSCF-DFIG-based wind power generation systems under normal grid conditions. Firstly, the wind power system is mathematically modeled by using the field-oriented vector-transformation of the stator and voltage-oriented vector of grid control. The rotor-side and grid-side converter controllers are designed in integration by utilizing nonlinearity adaptive control technology. The theoretical analysis demonstrates that under variable wind-speed, uncertain parameters and the external disturbances, the proposed controller can guarantee the wind power system to achieve the maximal absorption of wind power, capacitor voltages of converter dc side remain constant and the converters in grid side output constant frequency constant voltage electric energy with unity power factor. Meanwhile, the effectiveness of the designed coordinated controllers is illustrated by the simulation results.The control strategy is investigated for variable speed constant frequency DFIG-based wind power generation systems on the fault ride-through (FRT) operation under unbalanced grid voltage conditions. Firstly, positive and negative sequence dq axis model is established by using symmetric-component method for DFIG under the unbalanced grid voltage conditions. Then, the nonlinear adaptive control method is used to design the rotor of the motor side of the robust adaptive controller, and the simulation is studied. Both theoretical analysis and simulation results show that the resulting closed-loop system with the proposed controller can not only realize the fault ride-through operation but also has good dynamic performance under transient imbalance regardless of the uncertain parameters, external disturbance.