Current sharing strategies for fault tolerant AC multi-drives

Thanks to an inner redundancy, AC Multi-Drives can be made fault tolerant with minor modifications of their structure. However, some additional components are generally required in order to create emergency current paths in case of a fault. According to a recently presented approach the amount of additional components can be reduced by exploiting healthy drives to support faulty drives. In this case current and power sharing among drives assumes a key role. The paper deals with some new current sharing methodologies for AC multi-drive systems, where a suitable interaction among healthy and faulty drives is exploited, in order to cope with one or more faults. Specifically, three different current sharing control methods are presented and evaluated by means of simulations and experimental tests, taking into account the effects of operations in fault conditions both on healthy and faulty drives.