Abstract:Aiming to diagnosis faults of power devices open circuit, a new fault diagnosis method based on extreme learning machine(ELM) and rules inference (RI) theories for NPC inverter is proposed. The paper analyzes the distinguishability of faulty mode with current output and make a classification according to theSdistinguishability. Then fault features is extracted from output current, and extreme learning machine is established to make primary fault diagnosis. If the primary result is the current undistinguishable fault, the rule inference based on information of bridge voltage is used to accurately locatethe fault components, which is the second level diagnosis. At last, the results of diagnostics show that the proposed method can diagnosis and detect the many fault patterns and that the method has a good performance of accurate positioning, simple structure, fast diagnosis and robustness.