Parallel Open-Circuit Fault Diagnosis Method of a Cascaded Full-Bridge NPC Inverter With Model Predictive Control

Abstract

In this article, a parallel open-circuit fault diagnosis method (POFDM) is proposed for cascaded full-bridge neutral-point clamped inverters (CFNPCIs) employing the model predictive control. It can be inferred that the open-circuit fault will cause abnormal capacitor voltage changes in the submodule. Therefore, eight count variables are configured to correspond to the eight Insulated gate bipolar transistors (IGBTs) for each submodule. In the POFDM, the eight variables count all the abnormal changes, and the variables corresponding to the healthy switches are cleared to 0. Then, the switch whose corresponding variable is first added to the maximum is diagnosed as the fault device. Because the independent and parallel structure is adopted, the proposed POFDM can diagnose not only a single fault but also multiple faults in different submodules. And it can be easily extended to CFNPCIs with arbitrary submodules due to its parallel structure and modular software. Finally, the feasibility and validity of the POFDM are verified on the experimental prototype.