Reduction of the Effect of Machine Saturation on the Quality of Self-Sensing Control

Saturation effects are one of the main challenges arising in rotor position estimation for a PMSM. In this article, a method to cope with saturation effects for SSC of PMSM is derived analytically. The applied SSC algorithm is based on a numerical optimisation of a residual which includes the inductance matrix of the machine. By taking the cross-coupling between the d- and q-axes into account, not only is the estimation error minimised, but also the application of SSC is enabled at heavily saturated operating points. This is achieved by using the additional information provided by the mutual inductance, which is used to model the cross-coupling. Furthermore, harmonic estimation errors caused by saturation effects are eliminated by applying a simplified analytical model of the harmonic components to the inductance matrix. With these approaches, the effects of saturation on the quality of the SSC are significantly reduced. Since both of these methods rely on exact knowledge of the machine's inductances, a technique to determine these is provided. All results are validated experimentally.