A Uniform Modeling Method Based on Open-Circuit Faults Analysis for NPC-Three-Level Converter

A uniform modeling method for the neutral point clamped (NPC)-three-level converter is proposed based on open-circuit faults analysis. The main contributions of this brief are twofold. One is the proposed model can represent the converter not only in the normal condition but also the abnormal conditions that open-circuit faults occurring in any insulated gate bipolar transistors. The other is the model can be used for real-time simulation purposes. First, the NPC-three-level converter is simplified to a switch equivalent circuit by introducing the switch functions. Second, when the open-circuit faults occur, current paths of the NPC-three-level converter are analyzed and the values of switch functions with the open-circuit faults in the converter are acquired. The values of the switch functions in normal condition are obtained as well. Then, the uniform model of NPC-three-level converter is established, which integrates rectifier, inverter, and DC-link models. The uniform model can represent the converter in normal condition as well as in open-circuit fault conditions. The effectiveness and accuracy of the proposed model have been verified by simulation and experiment results.