Optimised operating range of modular multilevel converters for AC/AC conversion with failed modules

AC/AC modular multilevel topologies, such as Modular Multilevel Matrix Converter, Hexverter, and Modular Multilevel Converter in back-to-back configuration can be still operated when one or more modules failed, even if no extra module was added for redundancy. This paper proposes two novel approaches for the operation of these converter topologies with a reduced number of modules in wind energy systems. For each topology, the remaining operating areas for different scenarios of failed modules are presented, and the influence on the annual energy production is discussed.