Harmonic Current Suppression Of Six-Phase Permanent Magnet Synchronous Motor

With the development of micro industrial manufacturing technology and modern control theory,multiphase AC drive system is widely used.Polyphase permanent magnet synchronous motor has the characteristics of strong fault tolerance and high power density,which can respond quickly when driven by frequency conversion.Due to the strong coupling phenomenon of polyphase motor,it is more difficult to restrain the current harmonic and increase the motor loss.The six-phase permanent magnet synchronous motor with 30 degree y-shift is selected for analysis,and its mathematical model and drive control strategy which can effectively suppress harmonic current are studied.Firstly,the stator winding structure of six-phase permanent magnet synchronous motor is analyzed,its mathematical model is deduced,the modeling method of double d-q transformation and vector space decoupling is deduced in detail,and the simulation model is built in Matlab / Simulink.This paper introduces the main six-phase voltage source inverter PWM technology under two modeling methods,including three-phase decoupling and two zero sequence signal injection PWM algorithm based on double d-q coordinate transformation,and traditional vector six phase SVPWM algorithm based on vector space decoupling.Secondly,the vector control system of six-phase PMSM under two coordinate transformations is simulated and analyzed to study the control ability and harmonic suppression effect of traditional vector control for motor drive.This paper introduces the model predictive control theory of modern control theory and analyzes its application in the control system of six-phase permanent magnet synchronous motor.Thirdly,a model predictive current control method based on virtual voltage vector is proposed for current harmonic suppression of six phase PMSM.In this method,three orthogonal subspaces generated by vector space decoupled coordinate transformation are analyzed.Combined with the model predictive current control theory,the voltage vector is combined to generate a virtual vector with zero effect in the harmonic subspace,instead of the basic vector for value evaluation.The effectiveness of the algorithm is verified by simulation.Considering the effect of harmonic subspace,the stator current harmonic of the system is greatly reduced,and the model predictive control method has better dynamic performance.Finally,the switch signals of traditional vector control and model predictive control system are analyzed.Aiming at the problem of variable switch signals of inverter,an improved model predictive current control method is introduced to optimize the switch frequency.This method reanalyzes and recombines the virtual voltage vectors proposed above,selects the switch vectors with different voltage amplitudes,and under the condition of satisfying the harmonic subspace voltage constraint,the synthesized vectors are symmetrically fixed after PWM modulation,achieving the effect similar to three-phase PWM signals.Finally,matlab simulation verifies the effectiveness of the method,further reduces the stator current harmonics,and improves the stability of the system.