Multistage Predictive Current Control Based on Virtual Vectors for the Reduction of Current Harmonics in Six-Phase PMSMs

Abstract

The most recent finite control set model predictive control (FCS-MPC) strategies for six-phase electric drives avoid the excitation of the secondary subspace by using virtual vectors to minimize the current ripple. However, these strategies can only control the fundamental current components, which adjust the machine flux and torque and leave the secondary current components unregulated, which should be zero during regular operation in order to reduce the losses in the machine. Due to this limitation and also due to the low impedance of the secondary subspace in machines with distributed windings, the stator currents might contain non-negligible low-frequency harmonics caused by small asymmetries in the machine, non-linear dynamics of the semiconductors in the power converters and back-EMF harmonics. This article proposes a novel multistage predictive current control strategy based on virtual vectors (MVV-PCC) for six-phase drives based on permanent magnet synchronous machines (PMSMs), which contains a fundamental and a secondary control stages that are responsible for tracking the reference currents in both subspaces separately. The obtained experimental results validate the effectiveness of the proposed strategy in the minimization of the current harmonics and the reduction of the torque ripple for different operating conditions of the six-phase drive.