Pseudo derivative feedback current controlled sensorless PMSM drive with flux-torque based mras estimator for low speed operation

In this paper, a simple and robust speed estimator and Pseudo Derivative Feedback (PDF-PDF) controller are proposed for sensorless PMSM drive to improve its performance at standstill and low speed regions. The speed estimator is formed using stator flux and electromagnetic torque based model reference adaptive system, which performs better during transient conditions and reduces steady state error for wide rotor speed variations which includes low speed regions. The proposed PDF-PDF controller reduces the overshoot and improves settling time of the system. The stability of the proposed estimator is verified through small signal model and the machine parameter sensitivity is also analyzed. The performance of the proposed estimator and controller is validated by considering variation in the low speed regions which includes standstill condition. The simulations are carried out through MATLAB/Simulink and it is also experimentally verified through FPGA controller based 1.2hp laboratory prototype PMSM drive. It is found that the maximum estimated rotor speed and position error are ±2 rad/s and ±1° respectively during low speed operation at transient and steady state conditions.