A three level NPC inverter fault detection and identification using voltage vector residual evaluation based on current path tracking method

Abstract

This research describes open circuit detection and fault location for active 3-level NPC (neutral point clamped) inverter switches during normal and connected to the neutral point. This work introduces the current path tracking method to correlate the operating mode of NPC inverter and switch status in abnormal and normal conditions. Furthermore, a hierarchal diagnosis approach is introduced for open circuit faults using output Voltage Vector Residual Evaluation (VVRE). The node potential and conduction path can be derived from the model to indicate the NPC inverter circuit faults. Two steps are involved in the diagnosis. First, OC fault can be determined by analyzing the difference between the reference voltage and actual voltage vector resulting from the specified current path utilization ratio. Therefore, using a current path state reconstruction method, we can distinguish faulty transistors with similar properties. The simulated results demonstrate the robustness and efficiency of the proposed approach.