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.
Abstract-The objective of this paper is to provide an overview of emerging technologies for modular power converter architectures for electric vehicles. Nowadays, the most common electrical drive-train architecture exhibits one single inverter which is directly tied to the battery. As a consequence, only one high-voltage battery module can be applied and the dc-link voltage of the inverter and its apparent power rating is directly dependent on the available battery voltage. To overcome this restriction, modern power converter architectures with a higher degree of freedom have been proposed. These architectures exhibit modular dc-dc converters to allow different battery technologies to be linked to drive inverters operating independently from each other. To make this development feasible, new components and technologies are evolving which enhance the efficiency over mission cycles while ensuring further integration of the power-converter architectures.Wide-bandgap power semiconductors enable high switching frequencies and miniaturization of passive devices. Smart topology enhancements and control methods allow a significant loss reduction, in particular at light loads, resulting in a higher efficiency of the drive train over the entire driving cycle. Highly integrated bidirectional battery charger systems with intelligent charging strategies inhibit battery degradation and provide opportunities for grid stabilization. It is demonstrated how these technologies are realized and implemented to contribute to the development of future electric vehicles.
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