Impact of Post-fault Reconfiguration Strategies on Neutral Point Clamped Multilevel Inverter Power Losses

Multi-level Inverters (MLIs) are becoming more prominent in industry, with the Neutral Point Clamped (NPC) topology being the most common. Much research has been performed on fault recovery strategies, including their impact on the power quality output from the inverter. Taking that one-step further, this thesis provides an exploration into the impact of post-fault reconfiguration strategies on power losses in the NPC-MLI. In order to facilitate this, a power loss modeling algorithm has been developed for all of the semiconductor devices in the NPC-MLI. This algorithm is an offline calculation based on only switching states, input voltage, and output current. As such, it is universal and can be implemented on any NPC-MLI, under any control strategy, and/or reconfiguration strategy. This algorithm has been implemented in MATLAB Simulink and is used to estimate power losses under healthy condition, faulty condition, and three different control based reconfiguration methods. The change in power loss distribution due to changing load conditions is also evaluated. A five-level NPC-MLI is built in hardware, tested, and evaluated with infrared thermal imaging to validate the capability of the model to estimate losses