Fault Tolerance Performance of Two Hybrid Six-Phase Drive Systems Under Single-Phase Open-Circuit Fault Operation

This paper discusses the fault tolerance performance of two hybrid six-phase drive systems under single-phase open-circuit fault. The topologies are considered to be hybrid because each of the two three-phase groups of the six-phase machine is connected to a different type of converter. One group is connected to a two-level converter and the other group is connected to a dual converter in an open-end arrangement. A compensation strategy is discussed in order to keep the rated operation even after the occurrence of the fault. The six-phase machine mathematical model after the fault is presented and utilized to elaborate the compensation strategy. Simulation and experimental results show the validity of the discussed solutions. It is observed that the use of the degree of freedom represented by zero-sequence components makes stator currents assume lower amplitudes after a single-phase open-circuit fault than the case in which these components are not present. This fact brings the possibility of operation with rated torque/power after the fault or lower reduction in torque/power to meet the thermal windings requirements.