Research On SVPWM Modulation Strategy Of Nine-phase Open-winding Permanent Magnet Synchronous Moto

With the development of motor control and power electronics,the multiphase motor drive system is widely used.Compared with the three-phase motor,the multi-phase PMSM has the advantages of higher power,lower torque ripple and more flexible control mode.At the same time,the open winding of the motor shows more degrees of freedom,higher utilization rate of bus and stronger fault tolerance than the traditional star connection winding.In this thesis,the driving system of nine-phase open-winding permanent magnet synchronous motor(PMSM)is taken as the research object,and the space vector pulse width modulation(SVPWM)strategy is studied under the power supply of H-bridge inverter.According to the winding structure of nine-phase open winding PMSM,the extended Park transformation matrix is derived when the motor winding is semi-symmetric.Then the mathematical model of the motor in the rotating coordinate system is established,and the motor drive system based on vector control algorithm is built according to the motor model.SVPWM modulation strategy of H-bridge inverter is studied.Firstly,the relationship between the switching state of inverter and the level state of motor winding is analyzed,and a simplified algorithm is proposed to express the voltage vector by using the level combination instead of the switch combination.On this basis,a series of optimization and screening of vectors are carried out to eliminate the inefficient energy vectors and retain the necessary efficient energy vectors,greatly reducing the number of vectors.Finally,the basic voltage vector distribution diagram is constructed.Three SVPWM modulation strategies are proposed to suppress harmonic components by freely combining basic voltage vectors to improve the characteristics of the modulation algorithm.A single vector modulation strategy is proposed according to the structural advantages of nine-phase open-winding motor.In order to improve the universality of the algorithm on the basis of suppressing most harmonic components,the combination of voltage vectors is optimized under off-line condition,and then the modulation strategy of combining seven vectors into two vectors is proposed.Based on the feasibility of further optimization of the modulation strategy,a multi-vector modulation strategy based on online operation is proposed.In order to verify the actual control effect of theoretical analysis,an experimental platform of nine-phase open-winding PMSM drive system was built,and a nine-phase H-bridge inverter was used to supply power to the motor.Based on DSP and FPGA as the core of the controller,the algorithm programs of vector control,SVPWM modulation and carrier modulation are written.Finally,the effectiveness of SVPWM modulation strategy designed in this thesis is verified by simulation and experiment.