Research On Four-phase Switched Reluctance Motor Direct Torque Control Algorithm

Switched Reluctance Motor(SRM)is a new type of motor that is extremely superior to conventional motors.SRM has been widely used in various fields such as household appliances,aerospace,and electronic machinery,especially in the field of electric vehicles,because it has many advantages such as simple structure,many controllable parameters,wide speed range,and so on,which has become a hot topic in recent years.Due to its inherent double salient pole structure,its torque ripple during operation is relatively large,which limits its practical application.In order to reduce the torque ripple,a four-phase switched reluctance motor is often used instead of a three-phase switched reluctance motor.For its control method,the direct torque control is to analyze the mathematical model of the motor in the stator coordinate system and directly control the flux linkage.The torque,oriented by the stator field,does not require rotor parameters,which greatly reduces the effect of parameter changes on the system performance,which can effectively suppress the generation of torque ripple.At present,the domestic study of four-phase switched reluctance motor direct torque control algorithm is much less than three-phase switched reluctance motor.Therefore,the study of four-phase switched reluctance motor direct torque control technology has certain application value.Four-phase switched reluctance motors have more switching states than three-phase switched reluctance motors,which also makes the control strategy more flexible and variable.Firstly,the thesis analyzes the direct torque control strategy in the two-level state of the flux linkage,and combines the cosine torque distribution function,through the joint action of two control strategies to study the inhibitory effect on torque ripple.In addition,due to the particularity of the phase angle of the four-phase SRM,the application of the three-level state of the flux linkage in the four-phase motor is studied,and the use of increasing the transition voltage vector to optimize the switching table is proposed and the switch table is redesigned.The above four designs were simulated using Matlab/Simulink simulation software.The simulation results showed that the direct torque control based on the cosine distribution function and the direct torque control of the three-level flux linkage can suppress the torque ripple better than the conventional two-level direct torque control of the magnetic flux chain.But in comparison,the three-level flux chain has the best effect in suppressing torque ripple.