An Improved Sensorless Control Method for IPMSM-Compressor Drives Based on the MRAS with Motor Parameter Variations

In order to estimate the fluctuating rotor speed of sensorless interior permanent magnet synchronous motor (IPMSM) with compressor load accurately, an improved model reference adaptive system (MRAS) method is proposed, in which the motor parameter variations are taken into account. A rotor flux oriented vector control is employed as the basic control strategy for the IPMSM-compressor drive. The sensitivity of motor parameters on estimated rotor speed in MRAS is analyzed, which shows that motor inductances have the greatest influence on the rotor speed estimation. Based on these analysis, a finite element method (FEM)-based model of IPMSM is built by the magnetic field analysis using JMAG software to obtain the stator inductance variations caused by different phase currents and rotor position. The stator inductance variations are used in the reference model of MRAS for accurate speed estimation. In addition, the rotor speed fluctuation caused by the compressor load could be lowered by the load matching motor output torque based on precise rotor position estimation. Simulation and experimental results demonstrate the feasibility and effectiveness of the proposed control method, which shows that the error between the actual rotor speed and the estimated speed is limited within a very low level