IEEE Transactions on Energy Conversion, Vol.23, No.2, 393-402, 2008
Combined flux observer with signal injection enhancement for wide speed range sensorless direct torque control of IPMSM drives
This paper proposes a motion-sensorless control system usingdirect torque control with space vector modulation for interior permanent magnet synchronous motor (IPMSM) drives, for wide speed range operation, including standstill. 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. High-frequency rotating-voltage injection with a single D-module bandpass vector filter and a phase-locked loop state observer with a new synchronization procedure are used to estimate the rotor position, which is needed only by the current model in stator flux observer at low 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 and tested. Extensive simulation results and significant experimental results provided good performance for the proposed IPMSM sensorless system in more than 1:1000 speed range, under full-load operation, from very low speeds (1 r/min experimental) up to rated speed.
Keywords:direct torque control (DTC);flux observers;motion sensorless control;permanent magnet;signal injection;state estimation;synchronous motor drives;variable speed drives