Synchronous frame current control of multi-phase synchronous motor - part II asymmetric fault condition due to open phases

In this paper, the synchronous frame current controller of a multi-phase synchronous motor with open phases is proposed. The proposed method can not only possess the superiority of a linear controller over the conventional hysteresis-type current controller but it also enables the current to be regulated without a steady state error. The key idea is that all the harmonics of the current and voltage, which can still contribute to the torque positively, can be equivalently represented as dc components even under asymmetric fault conditions. Through out this paper, a five-phase synchronous motor with one open phase is used as a practical example and the basic concepts can be easily extended into an n-phase ac motor with multiple open phases, which has the arbitrary number or configuration of the remaining healthy phases. Experimental results prove the validity of the proposed modeling and control algorithm.