FOC Transformation for Single Open-Phase Faults in the Five-Phase Open-End Winding Topology

Abstract

Many critical five-phase permanent-magnet synchronous machine drive systems require operation after a single open-phase fault. The single dc supply open-end winding inverter topology allows for the injection of four unbalanced phase currents to better optimize the postfault machine torque after this fault. However, all previously published field-oriented control schemes send varying current references to the proportional–integral (PI) current controllers when controlling four unbalanced phase currents. This makes the design of the PI controllers considerably difficult as each machine operating point will require a different gain to accurately track the varying reference with minimum ripple. Consequently, this paper proposes a new postfault transformation matrix that obtains constant current references for any given set of four unbalanced sinusoidal phase currents. This facilitates easy design of the PI current controllers as the steady-state error can be reduced to zero in a user-defined response time for all operating points. This current control technique is the first to be designed specifically for the case of an open-phase fault to a five-phase open-end winding system.