Research On ZSC Suppression Strategies Of Open Stator Winding Permanent Magnet Synchronous Machine

Permanent magnet synchronous motor has been widely applied in industrial and military areas due to its high torque current ratio,small inertia,high control precious and high efficiency.And the structure of open stator winding permanent magnet synchronous machine is proposed as the electric drive system develops towards high-power rate.The open stator winding permanent magnet synchronous machine can be categorized into two types according to the fact that whether the same voltage source voltage(VSC)is adopted for the two converters,i.e.,the open stator winding permanent magnet synchronous machine with the same VSC and the open stator winding permanent magnet synchronous machine with the isolated VSC.The ZSC exists in the structure of OSW-PMSM with the same VSC.Hence,how to suppress ZSC is always the research hotspot.This article is also developed on the suppression of ZSC.In this paper,the mathematical model of open stator winding permanent magnet synchronous machine with same VSC is derived,especially the model of zero-sequence loop and the corresponding equivalent circuit.Through the analysis of the equivalent circuit of zero sequence,it can be found that the ZSC is produced simultaneously by the third harmonic back electromotive force and common mode voltage of the two inverters.Based on this point,this paper proposed the method to suppress the ZSC by redistributing the reference voltage into two parts for the two inverters.The constraint conditions of the two subsidiary reference voltage are obtained by setting the common mode voltages of the two inverters to be cancelled out by each other.Further,the extra control loop is set to suppress the ZSC.According to the theory of volt-second balance,the relationship between the adjusting time of zero basic voltages and the reference voltage of zero sequence is obtained.Then in the modulation process,the adjusting time is applied in the arrangement of the duration time of zero basic voltages to suppress the ZSC,which is revised in the modulation module of the system in Matlab/Simulink.Finally,the two strategies are verified through the simulation results in Matlab/Simulink,which proves to be effective in suppressing the ZSC.Besides,the modulation range of the two methods is analyzed.