Open-Circuit Fault-Tolerant Control Methods for a Multiphase Permanent Magnet Machine
thesisposted on 11.01.2022, 14:39 by Ali Akay
This thesis focuses on the open-circuit fault-tolerant (OCFT) control of a multi-phase machine to increase their reliability. There are several OCFT control method in the literature. First developed OCFT control methods focused on a control method that does not need a change on the drive system. However these developed methods had very high resistive loss. In the following years, new methods were developed to obtain a minimum ohmic loss. Nevertheless, these methods were developed up to two phase OCFT conditions. This thesis presents three different solutions for the open-circuit fault conditions, so the five-phase machine can run up to three phase OCFT condition. These methods had also minimum ohmic losses compared to the existing methods, and were developed by using the current space vector (SV) theory, rotating magnetomotive force (MMF) of a machine and d-q (direct-quadrature) axes currents. In the first developed method,the vec-toral sum of current SV in sinusoidal machine is a constant resultant SV. This resultant SV has been reobtained under OCFT conditions. Each phase produces two MMF terms; a pulsating and a constant term. The sum of these pulsating parts is zero under healthy condition. However, this is not zero under open-circuit fault conditions. A solution has been found to eliminate these pulsating parts in the second method. D-q axes currents are smooth when there is no fault in the machine. Nevertheless, these currents pulsates under faulty conditions. In the third developed method, a solution has been proposed to obtain a smooth d-q currents for OCFT conditions. This thesis also presents a solution to reduce the torque ripple for healthy and OCFT conditions. These developed methods has been validated by using an finite element analysis (FEA) software.