Space-vector-modulated for Z-source three-level T-type converter with neutral voltage balancing

In this paper, the Z-source three-level T-type converter (3LT2C) is proposed for low-voltage applications. The Z-source 3LT2C basically combines the positive aspects of the Zsource two-level converter with the advantages of the Z-source neutral point clamped (NPC) converter. The traditional space vector modulation (SVM) technique for Z-source 3LT2C produces the desired voltage transfer gain with minimized switching loss, but cannot deal with neutral-point potential (NP) balance issue. Therefore, an improved SVM method considering this coupling problem for Z-source 3LT2C is proposed. The method simplifies the space-vector diagram of a Z-source 3LT2C into that of a Z-source two-level converter. In order to obtain NP balance, the time of the conventional symmetric SVM is changed by properly adding or subtracting a percentage of the minimum gate-on time. The upper-shoot-through and lower-shoot-through states can be inserted into the improved symmetric SVM, which gives a large amount of benefits, both in boosting ability, NP balance and switching loss. The considerate stable NP voltage and the boosting gain have been proven in experimental from a prototype converter.