| With the rapid development of China’s urban rail,the permanent magnet synchronous motor(PMSM)traction system has begun to receive widespread attention.Compared with the three phase PMSM traction system,the multi phase PMSM has many significant advantages:higher power density,smaller volume and superior fault-tolerance;small output torque ripple and low operating noise;increased control freedom and richer control strategies.In this paper,a five-phase internal PMSM is taken as the research object,based on the maximum torque per ampere control and the vector control algorithm,the inductance parameter identification and multi-mode modulation are studied.This modulation scheme combines space vector pulse width modulation.(SVPWM)and selected harmonic elimination pulse width modulation(SHEPWM).And a multi-mode modulation switching algorithm is developed to overcome the torque and current impact caused by commutation between different modulations.Firstly,this paper deduces the mathematical model of five-phase PMSM in different coordinate systems,analyzes the working principle of five-phase inverter and the distribution state of five-phase space voltage vector,and summarizes the distribution rule of 32 space voltage vectors in fundamental wave space and harmonic space in detail.Secondly,the principles of vector control and maximum torque per ampere control are studied,and combined with the characteristics of the five-phase internal PMSM system,the field oriented control strategy of five-phase PMSM based on the maximum torque per ampere control is introduced;In order to reduce the dependence of the control system on the inductance parameters and enhance the system stability,the principle of recursive least squares with forgetting factor(FRLS)is analyzed,and combining with five-phase PMSM mathematical model,a FRLS-based inductance identification algorithm is discussed.By using this algorithm,the direct-axis inductance L_d and the quadrature-axis inductance L_q of the motor can be identified online.Thirdly,two SVPWM schemes,the nearest two-vector SVPWM(NTV-SVPWM)and the nearest four-vector SVPWM(NFV-SVPWM)for five-phase PMSM are studied.And the salient features of two modulation schemes are compared.The basic principle of SHEPWM scheme is studied,the solving process of switching angles in five-phase SHEPWM scheme is derived in detail.Combined with the characteristics of SVPWM and SHEPWM schemes in five-phase system,a multi-mode modulation scheme for five-phase system is designed,and based on the equivalent circuit model of PMSM,the multi-mode modulation switching algorithm is studied,which overcomes the problem of torque and current shock caused by switching between different modulation modes.Finally,DSP+FPGA controller is designed and built in conjunction with the RT-LAB experimental platform.The proposed algorithm is verified by hardware in the loop and the experimental results show that the adopted schemes are effective and correct. |
