Research On An Open-winding Harmonic-current-excited Brushless Synchronous Machine And Control Technology

The excitation magnetic field of permanent magnet synchronous machinecannot be adjusted, while for small and medium sized electric excitationsynchronous motor, the brush brings a series of problems. The paper proposed anew type of harmonic current excited brushless synchronous machine based on anopen winding pattern, which could not only adjust excitation magnetic fieldconveniently, but also removed the slip ring and brush. So it has important academicsignificance and practical value. This machine was studied by the theoreticalanalysis, system simulation and experiments systematically.Firstly, through the theoretical analysis of the armature magnetic field, themechanism of harmonic winding induction electromotive force was expounded.And the principle of harmonic excitation was verified by the finite element analysis,which laid a theoretical foundation for follow-up study.Then on the basis of traditional electric excitation synchronous machine, theharmonic excitation synchronous machine was designed. The influencing factors,including the turns of harmonic winding, arc coefficient, the thickness of the poleshoe, were analyzed. The effect of exciting current ripple was studied and the effecton the exciting current by filter capacitor was analyzed. With the theoreticalanalysis and finite element analysis of the tooth harmonic magnetic field and highorder harmonic magnetic field, the machine structure was optimized, which madethe structure be more suitable for the operation of the harmonic excitation.According to the special requirement of the stator currents, this paper putforward a PWM modulation strategy, which injected the third harmonic modulatingwave to the middle hexagon vector SVPWM. This strategy realized the decouplingcontrol of fundamental current and the third harmonic current. The MATLABsimulation model of the harmonic excitation synchronous machine and its controlsystem was established and the simulation results verified the validity of the motormathematical model and the effectiveness of the proposed control strategy.Finally, the prototype of harmonic-current-excited brushless synchronousmachine was made and the hardware experimental platform of control system wasset up. The experiment results verified the validity of the principle of harmonicexcitation and the effectiveness of the control strategy, which also confirmed thefeasibility of this novel machine.