A High Frequency Square Wave Harmonic Excitation Control Strategy for Self-Excited Synchronous Motors

Electrically excited synchronous motors are widely used in industrial automation, wind turbine power generation, transportation and other fields due to their advantage of being free of rare earth materials. However, traditional harmonic excitation schemes choose low order harmonics of the fundamental wave for excitation, which makes it impossible to completely decouple the excitation current from the fundamental wave and results in significant torque ripple. This paper proposes a novel square wave injection type harmonic excitation control strategy. This strategy can change the induced voltage generated at the rotor side by changing the amplitude and frequency of the injected voltage square wave, and then adjust the excitation current on the excitation winding after passing through the rectifier system behind the harmonic winding. A multi-phase self-excited motor experimental platform based on the proposed strategy has been established. The experimental results verified that the strategy can flexibly adjust the excitation current and output stable torque.