Three-Level Optimized Pulse Patterns With Reduced Common-Mode Voltage

This paper proposes the computation of three-level optimized pulse patterns (OPPs) with reduced common-mode voltage (CMV) over the whole range of modulation indices. Limiting the CMV, however, gives rise to increased current harmonics. To mitigate this, the OPP optimization problem is reformulated to allow for symmetry relaxations and multipolar switch positions. In doing so, the current harmonics not only remain low, but they are occasionally even lower than those of traditional OPPs. The presented numerical results, based on a medium-voltage (MV) drive consisting of a three-level converter and an induction machine, demonstrate the benefits of the proposed approach.