YU Ji xian, YAN Gang feng, ZHANG Bin

 

(College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China)

 

 

Abstract: In order to solve the problem of high cost, low reliability, being susceptible to interference and difficult to applying in a complex application environment caused by the traditional mechanical encoder to AC drive system, a novel method to estimate speed based on model reference adaptive system (MRAS) was presented. Mathematical model of permanent magnet synchronous motors(PMSM), speed closedloop control method and current sensorless control technology was studied. PMSM itself was considered as reference model and the stator current equations were considered as adjustable model containing variable speed. Adaptive law is designed based on Popov stability theory. When two models were equivalent, the estimated speed converges to the real value. Thus the rotor position can be estimated from integrating of the speed. Experiment and simulation results indicate that application of this method can overcome the problems of mechanical encoder and accurately estimate the speed in AC drive system, and that both static/dynamic performance and robustness is improved.

 

Key words: permanent magnet synchronous motor (PMSM); speed estimation; model reference adaptive system (MRAS); sensorless control; stability