Sensor-Less Drive of Ultra-Low Inductance SPMSM With DC-Link Single Current Sensor

This article presents a single current sensing method that achieves minimal current reconstruction errors, even at extremely low-speed region. In vector control applications, a drive system that combines single current sensor with position sensorless techniques is attractive as it minimizes the use of sensors. The current reconstruction method using the DC current measurement method introduces current reconstruction errors because of the sampling timing of single current sensor method. Moreover, current dc current measurement method has a dead zone where current reconstruction is not possible, leading to pronounced current ripple during the avoidance process. In the case of ultra-low inductance motors, the increase in current ripple exacerbates the drive performance, especially at low speeds. When the single current sensor method and sensorless drive are applied to an ultra-low inductance non-salient pole synchronous motor, it can lead to operational failures due to high current ripple and current reconstruction errors at low-speed region. This article proposes a technique to improve the performance in the low-speed region when current reconstruction method using dc current sensor and sensorless techniques are used together by eliminating dead zone in the low-speed region minimizing current reconstruction errors with a model-free method. The current reconstruction performance, sensorless startup, and operation performance have verified through experiments.