Torque Estimation Based on An Improved SOGI-FLL for IPMSM

Applications using motors often require precise control of output torque. However, direct measurement of torque can be costly and unreliable. Therefore, significant research attention has been given to the development of torque estimation methods to overcome these limitations. This paper presents a methodology to design a high precision torque observer for interior permanent-magnet synchronous motor (IPMSM) by implementing the discrete-time flux observer based on an improved second-order generalized integrator-frequency-locked loop (SOGI-FLL). In this scheme, an easy-tuning FLL is proposed as the speed estimator without extra signal estimation compared to previous FLL. Additionally, with aim to improve the estimation performance at sampling-to-fundamental frequency ratios, the discretization method of SOGI-FLL is illustrated and its validity is confirmed in frequency domain by Bode diagram. Experimental results show that the estimation accuracy of electromagnetic torque is dependable even at low sampling- to-fundamental frequency ratios.