Discrete-Time Modeling of Interturn Short Circuits in Interior PMSMs

This article describes the discrete-time modeling approach for interturn short circuits in interior permanent magnet synchronous motors with concentrated windings. The derived model has been designed to embody a tradeoff between precision and complexity, facilitating model-based fault diagnostics and mitigation. A continuous-time model incorporating universal series-parallel stator winding connection and radial permanent magnet fluxes is developed in the stator variables and transformed into the rotor reference frame, including also the electromagnetic torque. The transformed model undergoes discretization using the matrix exponential-based technique, wherein the electrical angular velocity and angle are considered time-varying parameters. The resulting model is subsequently expanded to consider the motor connection resistance via perturbation techniques. In the laboratory experiments, we validate the dynamical properties of the derived model by comparing its outputs with the experimental data and waveforms generated by the forward Euler-based approximation. We thus demonstrate the improvements over the conventional discretization.