Research On High Efficiency Control Strategy Of Switched Reluctance Motor Used In Electric Forklift

Switched reluctance motor(SRM)has the advantages of simple structure,low cost,high reliability,no need of rare earth permanent magnet materials,and easy to realize four quadrant operation.It is very suitable for driving electric forklift.However,the serious torque ripple of SRM and the single energy conversion mode of power converter limit its application in electric forklift.Aiming at the problem of energy conversion and recovery in SRM drive system of electric forklift,a new design method of integrated power converter is proposed to realize flexible energy conversion.In this method,interleaved bi-directional DC-DC(DC / DC)converter is used as the front-end circuit of traditional SRM power converter.By changing the on-off mode of bi-directional DC / DC converter,SRM can be flexibly switched between electric mode and regenerative braking mode.At the same time,the new integrated power converter adopts the hybrid energy storage of super capacitor and lead-acid battery,which can quickly recover the SRM braking energy in the process of electric forklift braking and lowering goods;in the process of electric forklift accelerating and lifting goods,it can quickly release the recovered braking energy and realize the efficient utilization of energy.Secondly,aiming at the torque ripple and noise of SRM used in electric forklift,the direct torque control strategy suitable for the new integrated power converter is studied.Through in-depth analysis of the mechanism of SRM electric and braking operation,a direct torque control method which can flexibly switch between electric and braking States is designed to meet the different working modes of the new integrated power converter.The control strategy can not only effectively reduce the torque ripple and noise during the SRM electric operation,and realize the smooth operation of the electric forklift,but also realize the efficient recovery of energy through torque matching during the SRM braking operation,so as to further improve the vehicle operation efficiency.In order to verify the new integrated power converter and direct torque control strategy proposed in this paper,the simulation model of 6 / 4 pole SRM drive system for electric forklift is established in matlabgsimulink,and the load characteristics of electric forklift and braking operation process are simulated.The results show that the new integrated power converter and direct torque control strategy can meet the requirements of frequent start stop and fast response of electric forklift,reduce the current ripple at the input and output,and improve the efficiency of energy recovery.Finally,the software and hardware design of the SRM drive system is completed,the SRM drive system experimental platform is built,and the operation of the control system is verified on a real machine.The experimental results show that the system has good speed regulation ability for regenerative braking and electric operation,stable speed operation,and small current ripple,which has a certain engineering practical value.