Contents I. Introduction
Modular multilevel converter or reconfigurable battery system topologies are gaining in interest within the field of transportation electrification or electric energy storage systems. Multilevel converters, in comparison to classical two-level converters, have several advantages as for example fault tolerant operation [1]–[3], increased drive cycle or partial load efficiency, when using low voltage MOSFETs in comparison to common IGBT solutions [4]–[9], and reduced electromagnetic emissions (EME) [10]–[12]. Nevertheless, due the cascaded or interleaved structure of the converter, the integrated battery packs are stressed with additional low order harmonic components, which reduces the battery efficiency in comparison to a classical two-level converter system [6], [13], [14]. It is often controversially discussed that these low order harmonics can cause a rapid aging of the battery cells, which has been proven to be wrong in [15], [16]. Integrating the power electronics even on cell or small battery pack level, the converter can additionally act as a part of the battery management system (BMS) [16]–[18], sometimes referred to as a reconfigurable battery system [17]–[19]. Using a multilevel converter with integrated batteries or an RBS drive train topology, each battery cell/module can be drained according to its individual capacity. In this manner the battery can be fully utilized even if individual battery cells have a reduced state of health. This in turn increases the actual life time of the drive train, since common traction batteries are typically replaced if the SOH drops below 80 %. However, an RBS typically needs an additional, dedicated propulsion inverter.
