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The d–q axis inductance is the crucial parameter for the interior permanent magnet (IPM) motor. In order to facilitate the design, analysis, and optimization of IPM motors, it is of great significance to develop an accurate and simplified inductance analytical calculation method. Among the existing calculation methods, the magnetic equivalent circuit (MEC) has advantages in the inductance calculation of the IPM motor due to the simple modeling, the fine processing of the saturation region and the visualization of the magnetic field distribution. However, the traditional MEC method is only applicable to the IPM motor with integer-slot distributed winding (ISDW) or fractional-slot concentrated winding (FSCW), while lacking of in-depth research on fractional-slot distributed winding (FSDW). The magnetic circuit topology of FSDW IPM motors is not as single as that of FSCW/ISDW IPM motors. It leads to problems in the traditional MEC method when dividing the d/q axis flux path in FSDW motors. To solve this problem and expand the applications of MEC method, a big-small pole space (BSPS) method is proposed, which divides the d-axis flux path according to the asymmetry of the d-axis magnetomotive force (MMF). Based on the divided flux paths, an improved nonlinear MEC model that considers the saturation of stator and rotor is established to calculate d- and q-axis inductances. The results of finite element analysis (FEA) verify the validity of the proposed MEC model with different geometry parameters. Experimental results of an 84-pole/360-slot FSDW IPM wind generator further confirm the validity of the proposed MEC model.

The reference vector strategy has been widely used in the model predictive control (MPC) to reduce the computational burden. However, the reference vector derivation as well as the predictive model are sensitive to the machine parameters. This article presents a robust MPC with Luenberger observer to compensate the localization error of the reference vector for a six-phase permanent magnet synchronous motor (PMSM) drive. First, the two-step synthesis technique is employed to increase the tracking capability in the primary subspace and reduce the harmonic currents in the secondary subspace. Then, the influence of the control set design on the robustness is investigated, and it is confirmed that the more densely the voltage vectors locate, the easier the erroneous vector selection occurs. The Luenberger observer is adopted to compensate the localization error of the reference vector caused by the machine parameter mismatch. Subsequently, the cost function is defined in the form of the voltage vector error directly, thus greatly simplifying the control structure. In this way, the steady state performance as well as the parameter robustness are enhanced significantly. Experimentations are conducted to verify the validity of the proposed method.