Magnet-flux-nulling control of interior PM Machine drives for improved steady-state response to short-circuit faults

This paper proposes a control method to null the magnet flux in an interior permanent-magnet (IPM) motor following short-circuit-type faults in either the inverter drive or motor stator windings. Phase-based control is employed to implement the flux-nulling-control method so that it is possible to take advantage of a zero-sequence current in order to minimize the current in the shorted phase. It is shown that phase-based control results in a smaller induced current than when employing a synchronous-frame dq0 current regulator. The induced torque is also less than that when employing a purposely commanded symmetrical short circuit in response to a short-circuit-type fault. In the paper, the complete magnet-flux-nulling-control algorithm is derived with reference to the proposed phase-current-control method. The impact of controlling the zero-sequence current on the resulting phase currents is presented. Both simulation and experimental results are presented, verifying the operation of the proposed methods.