Online Estimation of Direct- and Quadrature-Axis Inductances Without Rotational Transformation for Finite Control Set PMSM Drives

Model-based finite control set (FCS) strategies require accurate inductance parameters but encounter challenges in updating these parameters online. To address this issue, a switching time-scale online inductance estimation method is proposed. This method leverages current derivatives and eliminates the need for fundamental inverter voltage, additional signal injection, or rotor position information, making it well-suited for FCS strategies. One key element of the proposed method is the introduction of position scalars, which contain both DC and second-harmonic inductance components. A generalized position scalars (GPSs) calculation method has been developed to ensure compatibility with arbitrary voltage vector sequences. The use of GPSs allows for the separation of the amplitude and phase of the second-harmonic inductance. Building on this separation, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$d$</tex-math></inline-formula>- and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$q$</tex-math></inline-formula>-axis inductances can be estimated without requiring rotor angle information and rotational transformations. An efficient GPSs table lookup process is designed, reducing the computational burden and facilitating online implementation. Moreover, the proposed method can operate with a zero <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$d$</tex-math></inline-formula>-axis current and under non-steady-state conditions without causing rank deficiency issues. Experimental results validate the accuracy and efficacy of the method across the entire operating range.