A Simultaneous Diagnosis Method for Multiple Faults of Modular Multilevel Converters Based on Residual Trajectories

Since the residual amplitude contains limited information, traditional model-based diagnosis methods have the problem of multi-fault confusion caused by the coupling of fault characteristics. Therefore, this paper proposes a simultaneous diagnosis method for multiple faults of modular multilevel converters (MMCs) based on residual trajectories. Firstly, the residual mathematical model under different faults is established and the variation law of time-domain characteristics and statistical characteristics of residual signals is revealed. Then, by combining the Pauta criterion and continuous outlier verification, a highly robust fault detection criterion is designed. Furthermore, a fault classification method based on the residual standard deviation-expectation trajectory is proposed, which can effectively identify IGBT open-circuit faults, current sensor faults, and arm inductor short-circuit faults. In addition, in order to locate multiple IGBT open-circuit faults, a fault location method based on the contribution rate of residual outliers is proposed. Finally, the effectiveness of the proposed approach is verified through simulations and experiments.