Double dq control strategy of DFIG based on passivity theory under unbalanced grid voltage

The paper analyzed the mathematical model of the converters of the DFIG under unbalanced grid voltage. A nonlinear control strategy based on passivity theory was advanced under the positive and negative sequence synchronously rotating frame which could achieve the different control targets by controlling the positive and negative sequence dq currents. The simulation results suggested that the nonlinear controller based on passivity theory could reject the 2^nd harmonic pulsations of the magnetic torque, active power and the DC voltage. The changes of the parameters had little influence on the controller. It showed that the controller had robustness It improved the ability to ride through the unbalanced grid voltage.