Improved Predictive Torque Control with Unidirectional Voltage Vector Selection of PMSM Fed by Three-Level Neutral-Point-Clamped Inverter

This paper proposes an improved predictive toque control with unidirectional voltage vector selection method for a three-level neutral-point-clamped inverter (3L-NPCI) fed permanent magnet synchronous motor. The proposed algorithm can restrict the candidate voltage vectors (VVs) within
$60^{0}$
of the space voltage diagram (SVD), which are the nearest to the flux trajectory for each
$60^{\mathrm{o}}$
flux sector. After the subdivision of the SVD and flux trajectory, the proposed method can keep VVs in one direction during the prediction process which can result in significant torque/flux reduction. Therefore, the proposed algorithm achieves superior performance to the conventional method which requires enumerating all 19 voltage vectors while significantly reducing the computational burden. The proposed FCS-PTC of PMSM has also other advantages, such as improved capacitance voltages balancing, small computation time due to the reduced number of admissible voltage vectors considered in the cost function, and easy implementation. The effectiveness of the proposed method is verified through simulation and experimental results.