Short-circuit fault mitigation methods for interior PM synchronous machine drives using six-leg inverters

This paper characterizes six-leg inverters to mitigate short-circuit faults for interior permanent magnet (IPM) synchronous machines. Key differences between bus structures in six-leg inverters are identified. For six-leg inverters employing two isolated DC links, it is shown that up to 75% of rated output power could be produced following a single-switch short-circuit fault. A magnet flux nulling control method is proposed as a response to stator winding type short-circuit faults. This control method results in a zero-torque fault response by the motor. The important influence of the zero sequence in both the motor and inverter structure is identified and developed for this class of fault. Simulation and experimental results are presented verifying the proposed magnet flux nulling control method.