Recent Advances in Sensorless Drive of Interior Permanent-Magnet Motor Based on Pulsating Signal Injection

This article presents the developments of the sensorless control of an interior permanent-magnet synchronous motor (IPMSM) based on signal injection for the last five years. At first, modeling of an IPMSM is discussed. In contrast to the conventional inductance-based voltage model, the flux model considering saturation and spatial harmonics of IPMSM is introduced. For the identification of the flux model, either finite-element analysis or experimental test is required. Second, based on the flux model, some sensorless control methods of IPMSM for the traction of a vehicle, where IPMSMs are heavily saturated for higher torque density, are described. In contrast to the belief that there should be a certain saliency for the sensorless control based on the signal injection, it is explained that sensorless control is possible even in a reversed saliency region. Third, the methods to decrease the magnitude of the injected signal itself are discussed together with the optimization of the frequency of the signal. The simulation and test results for typical automotive-grade IPMSMs with several sensorless methods exploiting square-wave signal injection are presented, and the physical meaning of the test results is discussed. Finally, future outlook based on recent developments is addressed.