Improved Flux Weakening Control of Doubly Salient Electromagnetic Motor Considering d-and q-Axis Voltage Harmonics

The parallel stator poles structure and concentrated field winding configuration of the doubly salient electromagnetic motor (DSEM) lead to the asymmetric three-phase flux paths and thus causing the significant
d
-axis and
q
-axis voltage harmonics. In the conventional flux weakening control methods, these
d
-axis and
q
-axis voltage harmonics are not considered, which will cause the deviation between the computed voltage and the actual voltage and reduce the dc-link voltage utilization. In this article, an improved flux weakening control method considering the
d
-axis and
q
-axis voltage harmonics induced by the asymmetric three-phase flux paths is proposed for the DSEM. First, the asymmetric three-phase flux paths of the DSEM are analyzed in this article. Then, the voltage equation considering the asymmetric three-phase flux paths is derived and verified. The current and voltage constraint are constructed and the reference current curves at different speeds are obtained through the proposed offline method. Finally, the proposed flux weakening control method is implemented on the 12/8-pole DSEM drive system. The experimental results indicate that the proposed flux weakening control method can improve the dc-link voltage utilization, effectively extend the constant torque region, and enhance the output power and torque capability of the DSEM drive system.