| Permanent Magnet Synchronous Motor(PMSM)has been widely used in industrial production,new energy vehicles,etc.due to its high power density and high efficiency.Therefore,the control of PMSM has become a research hotspot.At present,the PMSM control system is very mature,but in some special occasions,the inverter needs to be fault tolerant.When a certain phase bridge arm of the inverter fails,the system will not work.Therefore,it is proposed to reconstruct the inverter after the fault into a three-phase four-switch topology to realize fault-tolerant operation of the inverter.In this paper,the theoretical study of the three-phase four-switch inverter power supply PMSM system is carried out,and the predicted direct torque control and the hybrid space vector modulation method are applied to the control system to minimize the PMSM torque ripple.Firstly,this paper analyzes the mathematical model of PMSM and three-phase four-switch inverter,and builds a three-phase four-switch inverter-powered PMSM direct torque control system based on the basic principle of direct torque control algorithm.The control system mainly introduces the working process of three-phase four-switch vector switch table and stator flux linkage and torque observer.By constructing the simulation model and analyzing its control effect,the rationality of the control algorithm is verified.Secondly,due to the poor power supply conditions of the three-phase four-switch inverter and the inherent shortcomings of direct torque control,there is a large torque ripple in the steady state operation of the system.In order to solve the problem of large torque ripple of PMSM in direct torque control,based on the idea of predicting direct torque control,a three-phase four-switch inverter-powered PMSM predictive direct torque control system is established.In this algorithm,the magnitude and phase of the voltage vector are predicted by the relationship between the electromagnetic torque and the stator flux linkage and the voltage vector,and the voltage vector is synthesized using a three-phase four-switch space vector modulation strategy.The simulation results show that compared with the direct torque control,the algorithm reduces the PMSM torque ripple during steady-state operation and maintains good dynamic performance.Thirdly,different zero vector synthesis methods in the three-phase four-switch space vector modulation strategy have different effects on PMSM torque ripple.In order to minimize the PMSM torque ripple in the predicted direct torque control system,a hybrid space vector modulation strategy is proposed in this paper.The effect of different zero vector synthesis methods on PMSM torque ripple is analyzed by the method of torque ripple RMS.At the same time,the sector is re-divided by a simplified engineering approximation algorithm,and the zero vector synthesis method used in each sector is obtained.The simulation results show that the hybrid space vector modulation can minimize the PMSM torque ripple in the predicted direct torque control system.Finally,this paper builds a three-phase four-switch inverter power supply PMSM control system experimental platform,and experimental verification of the proposed direct torque control strategy and hybrid space vector modulation strategy.Through the analysis of the experimental results,the proposed control strategy can effectively solve the problem of large PMSM torque ripple. |
