Seamless Start-up of Loaded PMSM Drive from Open-Loop Id/F to Sensorless FOC

Position-sensorless control of permanent magnetic synchronous machines (PMSMs) are widely used in industry. It is difficult to identify the rotor position at low speed and startup stage in EMF-based sensorless control. The position open-loop IF combined with sensorless approach is the main strategy. However, the traditional direct transitioning from open loop to close loop introduces current and torque disturbance, which undermine the sensorless startup process, especially in loaded conditions. To solve this transitioning problem, this paper proposes a seamless shift method from I
d
/F open-loop start-up mode to sensorless closed-loop control in a loaded PMSM drive system. Based on the PMSM voltage model in the synchronous frame, mathematical results are derived with current state feedback decoupling and PI control scheme. To eliminate the current and torque disturbance at the transition of shifting from I
d
/F open loop to the sensorless closed loop, the stator voltage of the machine should be continuous. Therefore, a control state reset (CSR) method is proposed in this paper to maintain the output voltage continuously. Simulation results validate the smooth shifting without large torque disturbance. Experimental results verify the proposed method on a dSPACE real-time control platform.