Dead Time Adaptive Expansion-Based Sensorless Restart Strategy for Free-Wheeling SPMSM Drives

This article proposes a novel rotational restart strategy based on the dead time adaptive expansion for the sensorless surface-mounted permanent magnet synchronous machines drive system. With the proposed method, the interval time of zero-voltage pulses (ZVPs) is replaced by the dead time and each pulsewidth modulation (PWM) period consists of the dead time and action time of ZVPs. By regulating the dead time based on the stator-current amplitude feedback, the stator current can be controlled within the reasonable setting range, which not only can achieve the adaptive selection of the action time and interval time of ZVPs, but also avoid the potential overcurrent and overcome the current sampling noise. Meanwhile, aiming at two continuous and discontinuous current modes caused by the inserted dead time, the corresponding calculation expressions of the rotor position are deduced in detail. Finally, experimental results indicate the effectiveness and feasibility of the proposed strategy.