Fault Tolerant Control and Reliability Assessment of Modular PMSM Drive Systems

This report proposes an approach to implement improved Fault Tolerant (FT) control in a modular Open Winding (OW) Permanent Magnet Synchronous Machine (PMSM) drive system. The report also proposes a reliability assessment on FT converter topologies and the effect of layering redundancy. An existing lab setup is used as a case study to create a new control system. The redundant case functions with multiple sets of phases, a fault will disable the faulted set leaving the sound phases operational.The new system aims to utilise all remaining sound phases (5 out of 6) in case of an OCF. Operating the drive system in this post-fault condition will leave the system unbalanced, leading to Common Mode (CM) voltage and current. The new system therefore has to operate with the remaining sound phases, whilst reducing the CM disturbance. It is expected that this can be achieved by modifying the control system. Expanding the control system from dq to dq0 allowed control of the zero-sequence current, the CMC.Applying the CMR control allows reduction of CMC in pre- and post-fault condition at nominal load. For post-fault this did result in a current overload of 344.21% in one of the stator phases relative to the pre-fault current. This overload should be taken into account when designing a machine for a specific applications by reducing the post-fault load or over-sizing the machine. The CMR control system proposes an approach to control the machine and reduce the CMC during post-OCF condition. The reliability assessment compared traditional VSI to OW to the extra switching leg converter. Each assessed for one, two and three sets of three phases, also for split and common DC bus. The extraswitching leg and OW topology showed the highest reliability across all phase set configurations. The application of a common DC bus has greatly reduced reliability compared to a split DC bus. The reliability gain of the extra switching leg and OW converter is relatively small compared to the traditional VSI, it is concluded that the traditional VSI is a cost effective converter for achieving FT, if applied redundant