Smooth Switching Technique for Voltage Balance Management Based on Three-Level Neutral Point Clamped Cascaded Rectifier

Abstract

This paper discussed the topology of in the three-level neutral point clamped cascaded rectifier (3LNPC-CR) for designing the Chinese Power Electronic Traction Transformer (PETT). To balance the DC-link voltage (Vdc) in 3LNPC-CR, a smooth switching technique is proposed in this paper. The controlling processes of each module are relatively independent when the proposed technique is applied in 3LNPC-CR. The proposed technique can keep the switching frequency constant and change the switch state smoothly while balancing Vdc. The Vdc balance ability is analyzed by calculating the unbalance degree of the loads. Simulation and experiment of three-module 3LNPC-CR are built, and then the effectiveness of the proposed technique is verified.