A current optimization model predictive control with common-mode voltage reduction for three-level T-type inverters

Abstract

This paper proposes a current optimization model predictive control with common-mode voltage (CMV) reduction (COMPC-CMVR) for three-level T-type inverters to suppress CMV and improve current quality without increasing the losses. The CMV is restricted within u_dc/6 by excluding voltage vectors (VVs) with high CMV. However, the reduction in VVs reduces the current quality. The neutral point (NP) voltage optimization interval is proposed in the COMPC-CMVR to improve the current control performance, where the grid current is the only control objective when the NP voltage is within the voltage optimization interval. The small and medium VVs are divided into P-type and N-type VVs to balance the NP voltage without weighting factors. On this basis, two novel candidate VVs sets are proposed. The COMPC-CMVR considers only four to seven feasible VVs in each control cycle, which reduces the computational burden. Finally, simulation and experimental results show that COMPC-CMVR performs well in terms of steady-state and transient responses. The COMPC-CMVR can effectively suppress the CMV and improve current quality without increasing the losses.