This paper deals with the detection of single battery or inverter switch faults during operation of a common and an active three-level neutral-point-clamped (NPC) inverter with a connected neutral point. Here, a main focus lies on the detection and localization of open circuit faults of the inverter's switches. Therefore, a fault detection algorithm, using a current estimator, and two fault localization algorithms, a pulse pattern injection principle and an online adaption of the space vector modulation, are investigated and verified through simulations and experiments. Also investigated is how the power-train can be operated under fault condition, so that the vehicle can drive with a limited maximum power using an adapted space vector modulation, referred to as "limp home" mode, to the next service station. It is shown, that an active neutral-point-clamped inverter can cope with any single short or open circuit fault of the inverter's switches without bringing the vehicle to standstill, whereas a generic neutral-point-clamped inverter loses controllability, if an open circuit fault at an inner switch occurs. Furthermore, both inverter types are able to be operated just with half of the DC link voltage in case of a failure in one part of the battery.

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