With increasing requirements of high power ratings and high reliability in electrified transportation and energy harvesting applications, multiple three-phase permanent-magnet drives, such as the dual three-phase permanent-magnet synchronous motor (DTP-PMSM) drives have attracted more attention in both academia and industry. With additional control dimensions, the DTP-PMSM can offer additional features of low torque ripples and high fault-tolerant capability. On the other hand, the carrier ratio, i.e., the ratio of switching frequency versus fundamental frequency, becomes low for high-power or high-operation-frequency motor drives. Such low-carrier-ratio operation brings challenges in large low-order harmonics, distinct control delay and coupling effects between d-axis and q-axis to control of DTP-PMSM, which suffers from much smaller inductances in harmonic subspace and more switching states.

For addressing the issues and improve the control performance of DTP-PMSM with low carrier ratios, this tutorial will investigate multiple advanced low-carrier-ratio modulation and control schemes for DTP-PMSM drives. The modulation schemes under investigation include multisampling space vector modulation (MS-SVM), selective harmonic elimination pulse width modulation (SHEPWM), and synchronous optimal pulse-width modulation (SOPWM), whereas the control schemes include complex vector-based deadbeat predictive control, model predictive control (MPC), and flux trajectory control-based model predictive pulse pattern control (MP3C). The theoretical principles and experimental results will be presented to compare the different control strategies for DTP-PMSM drives with low carrier ratios.