Wide speed-loop range tuning technology for sensorless control of PMSM based on signal injection and stator flux observer

Mechanic position transducer will bring a lot of disadvantages in permanent magnet synchronous motor drive system. In this paper, a method to observer rotor position which is based on high frequency signal injection and stator flux observation is presented. The carrier signal is injected in the stator, and the rotor position error signal is extracted from the carrier current with saliency tracking for low-speed. Then it is processed by phase-lock-loop, which yields position estimations. A novel stator flux observer with variable structure uses a combined voltage-current model with PI compensator for low-speed operations. As speed increases, the observer switches gradually to a PI compensated closed-loop voltage model, which is solely used at high speeds. A new rotor speed estimator for the whole speed-loop range, based on the stator flux speed estimation with a new dynamic correction depending on estimated torque, is proposed. The Extensive simulation and experimental results provided good performance for salient-pole PMSM sensorless system.