Correlated Inductance Modeling and Estimation of Permanent Magnet Synchronous Machines Considering Magnetic Saturation

For permanent magnet synchronous machines (PMSMs), magnetic saturation is a key challenge to parameter estimation and saturation modeling using polynomials is popular with dq-axis inductances estimated independently. However, dq-axis inductances are mathematical terms derived from stator frame and are indeed correlated, which is not fully explored for improving estimation performance. Hence, this article proposes a correlated inductance model to represent the relationship among dq-axis inductances and model their nonlinear variations with respect to stator currents due to magnetic saturation. The idea is to model the saturation in the stator frame and derive the correlated inductance model in the rotating frame. The estimation model is established based on the correlated inductance model, in which dq-axis inductances are represented using the same components and the correlation can be fully explored to improve the estimation accuracy. Moreover, the proposed estimation approach does not involve the division by the dq-axis currents, which can ensure the estimation accuracy especially under conditions with small current magnitude. While existing methods often involve the division and result in limited accuracy under such conditions. The proposed approach is evaluated on two test machines and compared with existing methods to demonstrate the performance improvement.