Current Harmonic And Torque Ripple Suppression In Dual Three Phase Permanent Magnet Synchronous Motor

Dual Three-phase Permanent Magnet Synchronous Motors(DTP-PMSMs)have been widely used in since it inherits the advantages of both the PMSMs and multiphase machines.However,large stator current harmonics and large torque ripple under magnetic circuit saturation and postfault operation in the DTP-PMSM system limit its further application.Based on the comprehensive consideration of the shortcomings of the current harmonic and torque ripple suppression technology and the limited research on high-frequency current suppression and torque ripple suppression under magnetic saturation in DTP-PMSMs,this paper aims to suppress the current harmonics and torque fluctuations in the DTP-PMSM system.Focusing on the low-frequency current harmonics which are dominated by 5th,7th current harmonics in DTP-PMSM,this paper suppresses them by designing the control schemes.The harmonic suppression strategy based on an Extended State Observer(ESO)are proposed by regarding the current harmonics as disturbance.The anti-disturbance ability and robustness of the proposed methods are verified by theoretical analysis.The analysis also shows that the control strategy based on ESO has better low-frequency harmonic suppression ability than the Proportional-Integral controller and Quasi-PR controller.The scope of application of the strategy based on the ESO is also explored,and it is proved that this strategy can effectively suppress the current harmonic components caused by magnetic circuit saturation,motor salienty,overmodulation region operation,dead zone,and voltage drop in the inverter.It can also be applied in a large speed range.Simulation and experimental results verify the effectiveness of the proposed strategy.Aiming at the high-frequency current harmonics distributed around the carrier frequency and its integer multiples caused by the action of switching devices in DTP-PMSM,this paper suppresses them by improving the Pulse Width Modulation(PWM)strategy.the distribution of high-frequency harmonics in DTP-PMSM are analyzed first.The harmonic suppression strategy based on the carrier phase shift strategy with periodic frequency modulation(PFM)and the strategy based on changing the sequence of the PWM wave are proposed.The former reduces the harmonic peak at the carrier frequency by shifting the carrier wave in one set of three-phase winding by 90 degrees,and with the help of PFM.The latter eliminates odd-order high-frequency harmonics by changing the orders of the Pulse Width Modulation(PWM)waves.The effectiveness of the above strategies is verified by simulation and experiment.Considering the torque ripple of DTP-PMSM under magnetic saturation,firstly,it is pointed out by Finite Element Analysis(FEA)that the low torque ripple advantage of DTP-PMSM is undermined when the magnetic circuit is saturated due to the change of motor inductance.The mathematical model of torque ripple considering the mutual inductance between d-q axis and dq-z1z2 axis is established.It is pointed out that the 12 th harmonic is the main component for the torque ripple of DTP-PMSM under magnetic saturation.On this basis,the torque ripple suppression method based on optimized harmonic current injection is proposed.The reference value of harmonic current is obtained by analytical method to suppress the torque ripple with minimum copper loss.And the reference values are affected by the real-time inductances.The influence of the magnetic saturation on the torque fluctuation is considered through the change of the inductance under different load conditions.The experimental results show that the proposed control algorithm can successfully suppress the torque ripple caused by magnetic saturation.The proposed strategy has good dynamic performance since the algorithm involves no iterative computation and is computationally effective.DTP-PMSMs are famous for their fault-tolerant capability.However,the complex modeling,high copper loss and torque ripple under post-fault operation limit their further application.In this paper,a fault tolerant control(FTC)strategy is developed based on the virtual healthy DTP-PMSM model for DTP-PMSMs under the open-phase fault(OPF)where the coordinate transformation,the modulation strategy and the controller structure remain unchanged under OPF,is adopted in the proposed FTC scheme.And the current references are derived with minimum copper loss.Comprehensive theoretical analysis shows the relationship between the controller output voltage and the actual stator voltage should be considered in the proposed FTC strategy otherwise distortion in torque and current will be introduced.The torque ripple suppression method under OPF based on voltage compensation and Quasi-PR controller is proposed.Simulation and experiment results prove the analysis and the effectiveness of the proposed strategy.