A Synchro-Perspective-Based High-Frequency Voltage Injection Method for Position-Sensorless Vector Control of Doubly Fed Induction Machines

In this paper, a novel salient autonomous high-frequency (HF) signal injection method of sensorless drive for doubly fed induction machines (DFIM) is proposed. The HF 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 HF 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 mentioned. The tracking performances during acceleration and deceleration, and sinusoidal perturbation are investigated. The feasibility of the proposed concept is verified by the experimental results with a 4-kW DFIM drive. The performances of the drive system are evaluated in various operating conditions, e.g., subsynchronous, synchronous and supersynchronous speeds, voltage sag, and flying start.