The Optimization And Development Of The Direct Torque Control In Switched Reluctance Motor Drive

The output torque of the Switched Reluctance Motor contains inherent ripple,thus the observation and modulation of the output torque is the focus of the recent research.The implementation of the Direct Torque Control increases the stability of the output torque,as well as promoting the response of the torque.The method is parameter-less and improve the whole performance of the Switched Reluctance Drive system.This paper proposes optimization methods of the defects remained in conventional Direct Torque Control,and combines it with other control method and power converter by some adjustments.These processes improve the performance and adaptation further.Firstly,the conventional Direct Torque Method is optimized.Negative phase torque would be produced if the conventional method was directly implemented in the Switched Reluctance Motor drive,though the torque is limited within the hysteresis band.Therefore,the phase current amplitude is large and the torque-ampere ratio will be decreased accordingly.The optimized method concentrates on the output torque control by newly divided sectors,newly built voltage vectors,and newly set selection standards without combined flux control.The coordinate effect of sectors and vectors avoids the production of phase negative torque to a great extent.A Simulink + Simplorer + Maxwell co-simulation model is established to verify the effectiveness of the new method.Experiments are also carried out on a 12/8 structure prototype.The simulation and experiment results demonstrate the good torque performance and high torque-ampere ratio.Secondly,the Model Predictive Control is combined with the Direct Torque Control to drive the Switched Reluctance Motor.The Direct Torque Control provides the sector sequence and the possible switch states whereas the predictive model predicts the state value and the controlled output value.In order to stabilize the real output torque,the cost function evaluates the results of each predictive input by the standard of the least error with the torque reference.The simulation and experiment results demonstrate the effectiveness of the proposed method.Lastly,for the aim of expanding the application and decreasing the cost,the Direct Torque Control is implemented on a universal power converter to drive the Switched Reluctance Motor.Due to the different structure of the converter and the operation mode of the machine,sectors and switch state groups need to be redesigned.The length of the sectors are assigned to guarantee the positive torque production of the working phase on the one hand,and to avoid the negative torque production of the serial phase on the other hand.The newly added freewheel sectors compromises the positive torque to minimize the torque ripple more effectively.The experiment results demonstrate that under this method,the output torque is sufficient and the torque ripple is minimized.