Passivity-based control scheme for doubly-fed induction generator under unbalanced grid voltage

Based on the mathematical model of doubly-fed induction generator (DFIG) under unbalanced grid voltage, the instantaneous active and reactive power represented by stator voltage and stator current were deduced detailed. Four simply kinds of stator and rotor current reference values according to the different control targets were calculated. Then the paper analyzed the DFIG possessed passivity characteristics from the energy point of view. Furthermore, a passivity-based current controller for DFIG under the positive and negative sequence synchronously rotating frames (SRF) was proposed, so the positive and negative currents of stator and rotor could track the current reference values independently. Simulation and experimental results show that the proposed passivity-based control (PBC) scheme could effectively eliminate the 2th pulsations in stator currents, rotor currents, magnetic torque, active and reactive power according to different targets, and could improve the uninterrupted operation of the wind power system under unbalanced grid voltage. Meanwhile the system could track the maximum wind energy faster and more robust.