Optimal fault-tolerant control with radial force compensation for multiple open-circuit faults in multiphase PMSMs - A comparison of n-phase and multiple three-phase systems

Abstract

Open-circuit (OC) faults in electric machines cause deviations from the desired torque and result in undesired radial forces, which cause vibrations and noise. Multiphase permanent magnet synchronous machines (PMSM) provide additional degrees of freedom (DOFs) for the control of the machine, which allows to (partially) mitigate the impact of OC faults. Therefore, in this paper, an optimal fault-tolerant control (FTC) strategy with radial force compensation is developed for multiphase PMSMs under multiple OC faults. It minimizes the torque tracking error, power losses, and radial forces. Optimized reference currents are generated based on a magnetic equivalent circuit (MEC) model, ensuring a high control accuracy even for motors with significant non-fundamental wave behavior and magnetic saturation. The paper proposes a control strategy that consists of a nonlinear feedforward term, a PI-based feedback controller, and an iterative learning control (ILC) concept. Measurements validate the effectiveness of the proposed FTC strategy on a test stand for multiple OC fault cases. The proposed FTC strategy is applied to a twelve-phase PMSM with a single-star multiphase system (1 × 12 configuration) and a multiple three-phase system (4 × 3 configuration). The advantages of the proposed approach are demonstrated by experimental results in comparison with a proportional integral resonant (PIR) control strategy as the scientific state of the art in the literature.