Modified model predictive torque control for a PMSM-drive with torque ripple minimisation

This paper presents an improved model predictive torque control (MPTC) scheme for a permanent magnet synchronous machine (PMSM). In conventional finite set model predictive control (FS-MPC), the optimal voltage space vector (VSV) is selected for application in the voltage source inverter (VSI) by the evaluation and minimisation of a cost function; however, the application of a single VSV in the whole control cycle leads to a relatively high torque ripple and a high sampling time is necessary to overcome this issue. In order to reduce these shortcomings without sacrificing torque reaction performance, a modified MPTC is proposed. First, in order to reduce the computational burden, a switching table is introduced for a reduction in the selection of the possible VSVs; further, to reduce the torque ripple, the duty cycle optimisation of a subset of VSVs available from the VSI is performed. The conventional FS-MPC and the proposed control scheme are implemented using a field programmable gate array, and are experimentally compared in terms of torque and flux ripple, current harmonics, and computational effort.