A synchro-perspective high-frequency signal injection method for position-sensorless vector control of doubly-fed induction machines

In this paper, a novel high-frequency (HF) injection method of sensorless drive for doubly-fed induction machines is proposed. The high-frequency voltage is injected into the rotor winding and according to the concept of synchro, the rotor position can be simply extracted from the phase difference among the stator current and the rotor current regardless of machine and grid parameters. In addition, the proposed scheme is robust against the disturbance of high-frequency stator voltage propagated from the grid. The vector phase-locked loop (PLL) technique is employed to calculate rotor position and rotor speed simultaneously and the global stability of the PLL is validated. The feasibility of the proposed concept is verified by the experimental results.