Improved Sliding-mode Observer for Sensorless Control of High Speed Permanent Magnet Synchronous Motor

Abstract

A novel sliding-mode observer (SMO) with phase-locked loop (PLL) structure is designed for the observation of speed and rotor position in sensorless vector control of high speed permanent magnet synchronous motor (HSPMSM). Compared with conventional SMO, the novel observer replaces sign function with sigmoid function with smooth continuity as the switching function. And by introducing the PLL instead of arctangent function rotor position estimation method, it can reduce the estimation error. In addition, the algorithm for simplified three-level Space Vector Pulse Width Modulation (SVPWM) five-stage vector synthesis is studied, which satisfies the performance of high speed permanent magnet synchronous motor control system and simplifies the complexity of the algorithm. The improved observer and algorithm are applied to the permanent magnet synchronous motor vector control system to realize the sensorless control. Simulation results show that the improved sliding-mode observer can suppress chattering problem and improve the accuracy of rotor estimation.