A Novel Method for Measuring High Frequency DQ-axis and Cross-coupling Inductances in Interior Permanent Magnet Synchronous Machines

In this paper, a novel method for measuring incremental inductances is proposed for interior permanent magnet synchronous machines based on both rotating and pulsating high frequency voltage injection techniques. It mainly includes three high frequency voltage injection stages, which are rotating voltage injection in the stationary frame, pulsating voltage injection in the d-axis, and pulsating voltage injection in the q-axis of the synchronous rotating reference frame. Instead of using conventional position observer to obtain the error angle between the actual rotor position and the d-axis for calculating incremental inductances, it only makes use of the amplitudes of high frequency currents. Thus, the proposed method is free of any delay effects caused by voltage generation and digital filters. Nevertheless, the impacts of delay effects and inverter nonlinearity on the proposed method are also analyzed. Comparison between the proposed method and the conventional method are carried out in terms of injection steps and accuracy. The results obtained by the proposed method show a good agreement with those by finite element analysis and are compared with those obtained by the conventional method.