Fault tolerant AC multi-drive system

The paper deals with an original control strategy for AC Multi-Drive (MD) systems able to mitigate failures on one or more drives, through a minimal system reconfiguration. In particular, fault tolerance capability is achieved by isolating the failed inverter legs and connecting together the neutral point of stator windings of all motors; moreover, control algorithms are modified in order to maintain vector control in faulted drives. Differently from other MD configurations, the proposed solution avoids the connection of the neutral point of the machines to the middle point of the DC bus, thus overcoming the drawbacks related to the DC bus ripple and DC bus voltage utilization. In the following, two different scenarios have been analyzed, and pros and cons of the proposed solution are highlighted through simulations and experimental results.