The Research And Design Of Discrete Frequency Soft Starter Based On DSP

With the development of moden control theory and computer control technology,electronic soft starter has been used in industrial production.The main control method is to change the trigger angle of the thyristor to complete the motor starting.triggering pulses in different ways lead different starting ways.Single limited current starting and ramp voltage starting control modes have gradually been eliminated.The discrete varible frequency soft starter has same topolgical structure with electronic soft starter,which increase torque while reducing the starting current of the asychronism motor through the new control algorithm.Therefore,the discrete variable frequency soft starter can be applied in high-load occasions which the electronic soft starter can not be competent.This thesis introduces the basic principle of three-phase regulating thyristor,and proposes the control method of discrete variable frequency soft start,and introduces how to change power frequency into different subbands using the symmetrical component method to calculate the maximum positive phase combinating of non positive component.Secondly,we analyzed the selection of the initial and transition frequency band.Then we studied the distribution of pulse trigger signal in each sub frequency band in detail.Finally,the power factor angle is used as the feedback signal in each sub frequency band in detail.Finally,the power factor angle is used as the feeback signal,which can retrain asynchrocism motor chattering near the rated speed.After theoretical analysis,we did simulation software,and by comparing the frequency of 13 and 7frequency divider,summarized the most suitable initial sub bands of high-load starting.We also compared the discrete variable frequency soft starter with the ramp voltage starting.We also compared the discrete variable frequency soft starter with ramp voltage starter and the limited current starter,and then we can see the discrete variable frequency soft starting control method has advantages the others do not have.At last,the thesis intriduces software and hardware design of the discrete frequency soft starting based on digital signal processor DSP28335 made by TI company,and proves the discete frequency soft starting the oretically and simulate through the physical exeriment platform.We found the experimental waveforms and simulstion waveforms are basically the same,so verified the feasibility of screte variable frequency soft starting.