Initial Position Estimation for Surface Mounted Permanent Magnet Synchro-nous Motor

Abstract

Rotor initial position is required before starting in permanent magnet synchronous motors (PMSM). High-Frequency Injection (HFI) is a common method for initial position estimation as well as during operation. However, the traditional HFI method is only applicable to the interior permanent magnet synchronous motors (IPMSM) because of the significantly different d-axis and q-axis inductance characteristics. Meanwhile, for the surface-mounted permanent mag-net synchronous motors (SPMSM), this distinction is not considerable. To solve this problem, Short Pulses Injection (SPI) uses series pulses that cause an Inductance Saturation Effect and then considers the feedback currents to estimate the rotor position. The disadvantage of this method is that the estimation time depends on the current response speed as well as requires the motor to be at the satu-ration boundary to ensure an apparent saturation effect. This paper proposes a combined method based on the above two methods. Ini-tially, the position of the sector containing the d axis vector is determined by SPI. Then, maintaining the voltage vector causes saturation, then the HFI is used to estimate the initial position. To evaluate the effectiveness, the method is simulated by 3D FEM ANSYS MAXWELL and MATLAB SIMULINK. Compared with existing methods, this method offers accuracy and speed, especially suitable for applications with large moments of inertia.