A rotor position and speed estimation method for sensorless control of permanent magnetic synchronous motor

This paper proposes a new rotor position and speed estimation method for sensorless control of PMSM in high speed range. In order to improve the dynamic performance of conventional back-EMF methods, the proposed method eliminates the Phase-Lock Loop (PLL) while at the same time, avoids the potential local loop that might cause system unstable in closed-loop sensorless control. Instead of directly filtering the fast-changing calculated rotor position signal, the proposed method first filters a slowly varying signal, i.e. the calculated initial rotor position, to obtain the estimated rotor position. Then the estimated initial rotor position is added to the calculated rotor position to form an unbiased estimation of rotor position. The simulation results of a typical 1.5MW direct drive wind turbine system illustrate that the steady-state performance of the proposed method is similar to conventional EPLL method but the dynamic performance for rotor position is considerably improved, owning to its forward structure.