High Efficiency Closed-Loop Startup Strategy for Sensorless Permanent Magnet Motor Drive

This paper introduces an efficient startup approach for a sensorless Permanent Magnet Motor (PMM) drive. The proposed method utilizes a closed-loop strategy aimed at minimizing output power to reduce the current needed for the application's load torque. A particular closed-loop PI controller is used to stabilize the applied current reference, with the motor's output power serving as feedback. In addition, a parallel acceleration feedforward algorithm improves control response during speed changes. This method lessens drive losses common in the open-loop sensorless startup, especially where traditional stator flux-observer models for position estimation are ineffective at zero or low speeds. The shift from the open-loop to closed-loop sensorless control is smoother and more reliable, keeping the motor current near its optimal level. The controller's design and simulation in a precise discrete transient model shows this method's benefits over traditional open-loop startups that use the motor's rated current. This is evident in enhanced motor drive efficiency and stability.