Natural balancing of the neutral point voltage for a three-phase NPC multilevel converter

This paper presents an analytical solution for the natural balancing processes of the intermediate Neutral Point (NP) voltage of a three level Neutral-Point Clamped converter. The work begins by identifying the principal driving forces that control this natural balancing process. It then uses this understanding to propose a passive balance-booster filter that substantially reduces the natural balancing time constant, without requiring active control intervention. The results are validated by both matching simulation and experimental results.