Time-Optimal Model Predictive Control of Permanent Magnet Synchronous Motors in the Whole Speed and Modulation Range Considering Current and Torque Limits

Abstract

Improving control dynamics and enabling maximum torque and power conversion for a given electrical drive are important target quantities of drive control algorithms. To utilize the electrical drive to its maximum extent during transient and steady-state operation, a time-optimal continuous-control-set model predictive flux control (CCS-MPFC) for permanent magnet synchronous motors (PMSMs) is proposed. This scheme considers torque and current limits as softened state constraints in the CCS-MPFC's optimization problem to prevent transient overcurrents as well as torque over- and undershoots during time-optimal operating point changes. Furthermore, the overmodulation range including six-step operation can be entered seamlessly to ensure maximum power conversion at high speeds. Fastest transients within the whole modulation range are enabled by a time-optimal harmonic reference generator. Here, the flux reference of the CCS-MPFC is complemented with a harmonic content that enables operation in the overmodulation region. Further, the reference is prerotated during transient operation to attain time-optimal control performance. Extensive simulative as well as experimental investigations for linearly and nonlinearly magnetized PMSMs show that, compared with state-of-the-art methods, time-optimal control performance in the whole modulation range without transient overcurrents as well as torque over- and undershoots can be achieved by the proposed control method.