Research on Smooth Voltage Balance Modulation Strategy in Three Level Neutral Point Clamped Cascade Rectifier

Abstract

Aiming at the unbalanced DC voltage of multi-module three-level neutral point clamp cascaded rectifier (3LNPC-CR), a smooth voltage balance modulation strategy is proposed in this paper to solve the problem of unbalanced capacitor voltage in modules and unbalanced DC link voltage between modules. On the premise of normal operation, the input level of each module must not change. The voltage balance effect of the universal voltage balance modulation and the smooth voltage balance modulation are compared and calculated. Simulation and experimental results verify the feasibility of this strategy.