Capacitor Balancing and Common-Mode Voltage Reduction of a SiC Based Dual T-Type Drive System Using Model Predictive Control

The dual T-type multilevel converter (MLC) is an advanced topology with a reduced switching device count compared to a conventional diode clamped converter. This paper proposes a reduced switching state model predictive control (MPC) of a dual T-type drive system considering the DC link capacitor balancing, the common-mode voltage (CMV) along with torque control of an open-ends induction motor. The proposed study addresses the CMV in two different scenarios; i.e., the CMV reduction (CMVR) and CMV elimination (CMVE). A Matlab simulation for the proposed drive system is presented. A dual T-type converter prototype based on Silicon-Carbide discrete MOSFET switch is designed, implemented, and tested in the laboratory. The proposed MPC scheme achieves the torque command as well as balances the dual DC links in an efficient manner. It is observed that the CMVE has some limitation compared to CMVR, particularly at rated speed operation. It is worth mentioning that the proposed reduced switching states technique could reduce the computation time from 5.5 ms to $140~\mu \text{s}$ for CMVR and $70~\mu \text{s}$ for CMVE. In addition, the results demonstrate the effectiveness of CMVR scheme in reducing the harmonic contents, the torque and flux ripples, and converter switching loss compared to the CMVE scheme.