Research On The Control System For Open End Winding Pmsm Based On Z Source Network

Permanent magnet synchronous motor(PMSM)has been widely used due to its excellent structure,high power density,energy saving and high efficiency.The three-phase winding of the motor has a traditional closed winding connection method and an open winding connection method.The open end winding permanent magnet synchronous motor(OEW-PMSM)can avoid the limitation of the power level of the switching device and solve the high voltage.This can solve the problems of electromagnetic interference,switching loss,and device safety and reliability in high-voltage and high-power motor systems.In the servo field,the Z source network can be used to increase the DC bus voltage to expand the speed range of the motor while avoiding the adverse effects of dead time.In this paper,the advantages of the two are combined to study the open-winding permanent magnet synchronous motor system based on Z-source network.The specific research contents are as follows:Firstly,the working mode of the Z-source network and the working principle of the buck-boost are studied.The different modulation strategies of the Z-source network formed by different zero-voltage vector insertion methods are compared and analyzed.The component parameters of the Z source network are analyzed and calculated,and the main circuit structure is optimized and improved.Secondly,a mathematical model of two topologies of common DC bus type and isolated DC bus type OEW-PMSM based on Z source network is established.The open-winding structure turns on the zero-sequence loop,and the influence of the third harmonic component in the counter-electrical mode needs to be considered in modeling.The voltage equation,flux linkage equation and electromagnetic torque equation are established.Decoupling obtains the equivalent circuit of d-axis,q-axis and zero-axis,which is convenient for analyzing zero-sequence loop and system control.Thirdly,the common mode voltage and zero sequence current of the common DC bus type OEW-PMSM based on Z source network are studied.The Z source network can increase the modulation ratio and avoid the common mode voltage component corresponding to the dead time,and analyze the voltage vector distribution of the dual two-level inverter and the common mode voltage caused by the voltage vector.According to the relationship between the common mode voltage component,the third harmonic back electromotive force component and the zero sequence current of the inverter output,the zero sequence current closed loop control is established to achieve the zero sequence current suppression.The simulation and experimental verification are carried out by using the 12-segment straight-through modulation strategy.Finally,based on the isolated DC bus type OEW-PMSM topology based on Z source network,the level of the output voltage of two Z source networks and the voltage vector distribution of the open winding motor are studied.The Z source is analyzed.The network output voltage ratio is 2:1 and 1:1.The problem that partial voltage vector may cause over-charging of low-voltage side Z-source network capacitor is studied.The modulation strategy of isolated OEW-PMSM system based on Z-source network is verified by simulation and experiment.