Fault-tolerant control of six-phase induction generators in wind energy conversion systems with series-parallel machine-side converters

Multiphase generators in multi-MW wind energy applications can be realized with a variety of possible topologies. Series connection of machine-side converters elevates the dc-link voltage for the same voltage rating of IGBTs, allowing medium voltage generation on the grid-side. On the other hand, parallel connection of machine-side converters provides fault-tolerant capability, enhancing the system reliability. The combination of series and parallel connection of machine-side converters simultaneously elevates the dc-link voltage and provides some fault tolerance to the system. This work discusses the series-parallel topology for six-phase induction generators and analyzes the fault tolerance capability of the topology. Theoretical analysis and simulations confirm that it is possible to obtain additional fault tolerance at the expense of some unbalance on the individual dc-link voltages.