Inverter Open Circuit fault diagnosis method based on ISMO for Improved Efficiency

Conventional methods for diagnosing open-circuit faults in three-phase voltage-source inverters (TP-VSI) are hindered by limited diagnostic diversity and slow response times. To address this issue, this paper proposes a fault diagnosis method based on an improved sliding mode observer (ISMO). The construction of the ISMO begins with the mathematical modeling of the TP-VSI, incorporating a new power switching function designed to reduce chattering. More importantly, new fault characteristics are extracted, by leveraging the average log-likelihood ratio based on the observer-estimated current and the actual current. Finally, a delayed switching adaptive threshold (DSAT) is developed using logical operations. The DSAT is designed to diagnose two IGBT open-circuit faults while enhancing adaptability to dynamic operating conditions. Experimental results demonstrate that the proposed method effectively identifies 21 types of open-circuit faults, achieving a diagnosis time of <75 % of the current cycle, with high accuracy and robustness.