Improved Model Predictive Control for Multimotor System Using Reduced-Switch-Count VSI With Current Minimization

A multimotor system supplied from the reduced-switch-count voltage source inverter (VSI) is considered in this article. First, an improved multiple vectors model predictive control (MV-MPC) scheme is proposed for driving
n
three-phase permanent magnet synchronous motors (PMSMs) by (2
n
+ 1)-leg VSI. To realize independent control of multimotor, a control period is partitioned into multi-interval, one per motor. In the proposed MV-MPC scheme, the quasi-optimal voltage vectors (VVs) are selected to replace zero VVs under the restriction of identical common leg switching states. Thus, a whole control period can be fully utilized to generate multiple active VVs for a motor. Moreover, the overcurrent in the common leg is discussed and addressed. Take the five-leg VSI as an example, the expression of overcurrent in the common leg is first derived. Next, a general overcurrent elimination method based on current phase regulation is designed for the multimotor system operating at an identical speed. Finally, the proposed MV-MPC scheme combined with the overcurrent elimination strategy is experimentally carried out. The test results indicate that the MV-MPC method can effectively reduce current ripple and achieve a faster dynamic response. The overcurrent elimination method can minimize the overcurrent regardless of the load conditions of the motors.