Study On Unipolar Sine Excitation Control Of Switched Reluctance Motor Based On Voltage Space Vector

Switched reluctance motor(SRM)has attracted extensive attention and research due to its simple structure,high fault tolerance,low cost and flexible control after the emergence of high power thyristor and the development of power electronics technology.It has been widely used in many fields such as home appliances,industry,aviation and so on.But its special double salient structure and control mode,because it will produce large torque ripple and electromagnetic noise,is limited in the field requiring high dynamic performance.Therefore,domestic and foreign scholars have successively carried out research on reducing SRM torque ripple.The torque ripple can be suppressed from the motor structure and control strategy optimization.So,in this paper,the research status of SRM is introduced.To improve the operation performance of SRM and reduce the torque ripple,this paper presents a unipolar sine excitation control for SRM based on voltage space vector in dq rotating coordination,in which stator three-phase windings excited by unipolar current consists of sinusoidal current with DC bias,and selecting the optimal voltage space vector considering the coupling between d-q-0 axes.In this paper,the finite element model of SRM is established by Maxwell software,and its electromagnetic characteristics and dynamic characteristics including transient magnetic field simulation,current chop control and angle position control simulation are analyzed.In order to establish a precise SRM mathematical model,the parametric analysis of phase current and rotor position angle is carried out to obtain the nonlinear flux and torque characteristic dataes of SRM,and then establish the nonlinear motor model by Matlab/Simulink.Finally,building the simulation of current chopping control to verify the correctness of the model.In view of the control strategy proposed in this paper,we introduce and derive the inductance equation and the torque equation in the mathematical model of the three-phase static coordinate of the switched reluctance motor,then,the mathematical model of the d-q rotating coordinate system is derived by the coordinate transformation.By analyzing the torque equation and voltage equation,we find that the internal relations among the torque,the current and voltage component of d-q-0axis,which can use voltage space vector to control phase current to accomplish the indirectly torque control.Aiming at the coupling problem of d-q-0 axis in voltage equation,a suitable voltage space vector is selected by calculating the variation ofvoltage and current on dq axis under different voltage space vector to realize the control of d-axis,q-axis and zero-axis current component,thus,realizing the indirect control of torque.The research of the torque equation has found that the three harmonic currents injected into the DC bias current can further reduce the torque ripple,and the feasibility of the control strategy and the correctness of the theoretical analysis are verified by building the concerned simulation.Finally,respectively introduce the hardware modules and the whole software framework of the control system.We experience CCC and the control strategy proposed in this paper by the experimental facilities mentioned above.It shows that the proposed control strategy can effectively control the winding current and realize the stable and reliable operation when suddenly loading or acceleration.Compared with the current chopper control,the torque ripple is smaller,and the torque ripple can be further reduced by injecting third harmonic current to dc bias.