MPTC of NP-clamped three-level inverter-fed permanent-magnet synchronous motor system for NP potential imbalance suppression

For neutral point (NP)-clamped three-level inverter-fed permanent-magnet synchronous motor system, the tuning process of weighting factors in the cost function of conventional model-predictive torque control (MPTC) is complex. Also, large imbalance of NP potential can cause the deteriorated performance of flux and torque. To solve these problems, an improved MPTC is proposed. This algorithm first uses the deadbeat principle to unify the dimension of torque and flux. Then, the NP potential term in the conventional cost function can be eliminated by introducing the partition control of NP potential imbalance, which also eliminates the whole process of tuning weighting factors. After that, under the large NP potential imbalance, sectors are dynamically divided by modifying the magnitude and phase angle of medium and small vectors to improve the performance of torque and flux linkage. The experimental results show that compared with conventional MPTC, the improved MPTC can achieve fast suppression of NP potential imbalance with reducing the fluctuation of torque, flux linkage and current when NP potential imbalance is large.