Research On Common Mode Voltage Suppression Of Permanent Magnet Motor Drive System Based On Predictive Control

With the continuous development of power electronic control technology,the motor drive system composed of permanent magnet synchronous motor and inverter has entered all aspects of our life.As a result,the harm caused by the common-mode voltage of the motor drive system has also attracted more and more attention.The common-mode voltage will not only affect the internal system,causing bearing corrosion,cable burst,control performance decline and other consequences,but also cause external interference in the form of radiation,affecting the normal operation of other equipment.Therefore,the suppression method of common-mode voltage is studied.It is very important for the development of motor drive system.In the traditional SVPWM modulation mode,the use of zero vector 000 and 111 is the root cause of the high amplitude common mode voltage generated by the inverter.Hardware suppression methods such as the use of multilevel topology or the addition of output filters will increase the design cost of the system,and the corresponding control methods need to be changed because of the change of circuit structure.The software suppression method using the zero-vector modulation algorithm will sacrifice the drive performance of the motor.Therefore,it is the practical goal to study the common mode voltage suppression algorithm to improve the control performance of the system while suppressing the common mode voltage.In view of the defects of the above suppression methods,this paper uses the idea of model predictive control to suppress the common mode voltage according to the conditions of many constraints,free vector selection,no axis beat and excellent dynamic response.Firstly,the mechanism of common-mode voltage generation is explored,its propagation path in the motor drive system is analyzed,and the equivalent circuit parameter simulation model on the motor side is established to study how the common-mode voltage causes shaft voltage and shaft current inside the motor,so as to obtain its essential characteristics.Then,we study the conventional suppression methods,including adding output filters,changing the inverter topology,and non-zero vector modulation and random PWM,and analyze the advantages and disadvantages of each method.In this paper,an improved two-vector MPCC method and an improved three-vector MPCC common mode voltage suppression method are presented.The former calculates and allocates the action time of the vector on the basis of the traditional single vector MPCC,and selects the second vector again in a control period.The variation of the common-mode voltage is introduced into the calculation of the two cost functions,and the common-mode voltage is taken as one of the conditions for optimization,which inhibits the amplitude of the common-mode voltage and improves the dynamic response performance of the system.The latter combines the control idea of non-zero vector modulated NSPWM,and in order to improve the problems of large current ripple and current distortion in dual-vector MPCC,the three non-zero vectors closest to the target voltage vector are selected in a sector to synthesize reference vectors,and the method of multi-vector synthesis of target voltage vector is used to reduce the poor control accuracy caused by not using zero vector.Current pulsation problem.Both methods are simulated and verified based on MATLAB platform.Finally,the PMSM common mode voltage suppression experimental platform is introduced,and the improved three-vector MPCC common mode voltage suppression algorithm is successfully implemented on the platform,and the effectiveness of the algorithm is verified by the combination of simulation and theory.