MTPA fitting and torque estimation technique based on a new flux-linkage model for interior permanent magnet synchronous machines

Due to the nonlinearity of the flux-linkage profiles of the interior permanent magnet synchronous machine (IPMSM), the conventional motor model cannot be used for both maximum torque per ampere (MTPA) control and torque estimation. This paper proposes a nonlinear flux-linkage model for IPMSM with eight coefficients to fit the real d-axis flux-linkage, q-axis flux-linkage, MTPA, and torque. The corresponding torque equation and MTPA condition are presented. The factors in the proposed model can be obtained by solving an optimization problem with the limited information from the machine instead of the measurement throughout the map. The comparison of the characteristics between the proposed algorithm and FEA data is illustrated.