A comparison of slip control, FMA control and vector control in DFIG converter

This paper developed three control schemes to coordinate maximum power extraction and voltage control for doubly fed induction generators wind turbines during wind fluctuation. Via PWM, the rotor-side converter can generate a controllable AC voltage with controllable magnitude and frequency. Based on PWM, control schemes: slip control, flux magnitude and angle (FMA) control and vector control are developed. Wind turbine aerodynamics are modeled in dynamic simulation and to obtain a lookup table for torque/power control. In slip control, the voltage is coordinated with torque via voltage/Hz type control. In FMA control, the inner feedback loops of rotor flux magnitude and angle are developed. Torque control loop is added outside the flux angle control loop while voltage control loop is added outside of the flux magnitude control loop. In vector control, the power control loop and voltage control loop are added as the outside control loops while the current control loops is designated as the inner control loops. The purpose of the voltage control is to keep a constant stator voltage, and the power/torque control is used to get maximum wind power under varying wind speeds. Dynamic performance and robustness of the three control schemes are analyzed via linear system analysis tools (Bode plots). Matlab-based time-domain simulations are performed to verify the analysis results and the proposed control schemes.