Control Strategy Of Switched Reluctance Drive System

In recent years,with the development of power electronics and microprocessor technology,the driving system based on switched reluctance motor(SRM)has attracted the attention of many scholars.As a new driving system,it has the advantages of simple structure,low cost,reliable operation,wide range of speed regulation,and has been widely used in electric vehicles,aerospace,industrial automation and other fields.But its doubly salient structure and nonlinear characteristics of the flux in the process of operation produced torque ripple,which limits the further application of SRM.How to effectively restrain the torque ripple has become a hot topic of research.therefore the thesis chooses the direct torque control strategy and torque sharing control strategy as the research direction,from the design of the driving system expounds how to achieve this two kinds of control theory,aiming at reducing the torque ripple.In the thesis,the development of switched reluctance motor(SRM)and the current research status of control strategy are introduced,the operating principle and mathematical model of SRM are also introduced.Switched reluctance motor with doubly salient structure leads to the operation of flux has nonlinear characteristics,and the magnetic circuit is very easy to saturate,it is difficult to accurately establish the motor model,analyze its magnetic properties by using the finite element method to get the flux and torque data,using the look-up table method to establish the motor model.establishing chopped current control system based on PID and analyzing operating performance,it can be found that the torque of the chopped current control strategy is stable,but the amplitude of the torque ripple is very large,the dynamic response to the load disturbance is slow.In order to reduce the torque ripple and improve the stability of the control system,Firstly,the direct torque control(DTC)of AC motor speed control is used for reference,combined with the switch state of switched reluctance motor's power converter to establish reasonable voltage space vector,DTC of SRM control torque of motor directly.Then through building simulation model and analyze its performance under various conditions,it can be found that DTC can effectively reduce the torque ripple,but the negative output torque of each phase in the operation reduces the operational efficiency of the motor.Then the another control strategy which has a effective suppression of torque ripple is torque sharing control strategy(TSC),The desired torque is assigned to each phase by using the torque sharing function,and the constant torque control of SRM is realized by the superposition of the phase torque,cosine sharing function is used in this thesis to realize torque sharing control of SRM.Then through building simulation model and analyzing its performance under various conditions found that the torque ripple of TSC is very small at low speed,and the fluctuation of torque amplitude is not large in high speed operation.Moreover,the control performance of speed and torque are good,the effect of torque ripple suppression is obviousFinally,the experiment platform of the SRD based on the DSP TMS320F2812 control chip is built,the software and hardware design is completed.