A Robust Inductance Estimation Method at Standstill Considering Magnetic Saturation

This article presents a seamless dq-axis inductance measurement method for permanent magnet (PM) motor drives at start-up in milliseconds taking magnetic and cross-saturation effects into account. The proposed method deploys a machine model that incorporates these saturation effects and high-frequency injection (HFI) to generate a 3-D/2-D mapping of inductances across all operating regions. Additionally, a unique current sequence injection is introduced for electric vehicles (EVs) and industrial applications where locking the rotor is not feasible. This injection method ensures that the resultant torques keep the rotor stationary throughout the estimation process. Further, the proposed method effectively mitigates the impact of inverter nonlinearity and digital delay on inductance estimation, a topic that is further elaborated upon. Additionally, the proposed offline method is extended to online type with or without the use of position sensor in the application. Experimental validation is conducted on different motors, demonstrating the accuracy of the proposed strategy in estimating the d-q inductances without the need to physically lock the rotor.