A Segmented-Rotor Switched Reluctance Motor And Its Direct Torque Control For The BSG Used In Mild Hybrid Electric Vehicles

With the problem of energy shortage and environmental pollution becoming more and more serious,the research of energy saving and emission reduction becomes more and more important.The belt-driven starter generator(BSG)technology is an important part of the mild hybrid vehicle technology,and it is of great significance for the research of energy saving and emission reduction.Compared with other types of BSG motors,switched reluctance motor(SRM)has become a hot research topic of BSG motors,because of its no permanent magnets,no wound windings on the rotor and its simple structure.In this thesis,the segmented-rotor SRM(SSRM)of BSGs is taken as the research object,and supported by the National Natural Science Foundation of China(U1564201)and the Outstanding Youth Project of Jiangsu Province(BK20180046).And ontology structure optimization,nonlinear modeling analysis,direct torque control(DTC)strategy and the prototype experiment are emphatically studied.The main research contents are as follows:1.The operation principle and mathematical model of the SSRM for BSGs are expounded,and the structural characteristics of the SSRM are introduced.In order to satisfy the requirements of rated torque and low torque ripple,the stator and segmented rotor pole arc angles,and segmented rotor groove depth of the SSRM are optimized.Then it is found as shown in the simulation results that the torque ripple of the SSRM reduces obviously after optimization analysis.In addition,the influence of the different winding connections on the output torque and torque ripple of the SSRM is analyzed.The results show that the output torque meets the design requirements when the winding connection is NSNSNSNS.Besides,the torque ripple of the SSRM is low relatively.2.The advantages and disadvantages of several common nonlinear modeling methods of the SRM are expounded.Under the premise of not using the rotor clamping device and position sensor,the electromagnetic characteristic curves of the SSRM is obtained by using torque balance method and simplifying second-order Fourier series.Moreover,the nonlinear ontology module of the SSRM is built by using cubic spline interpolation.At last,compared with the angle position control(APC)method,the simulation results show that the proposed method can achieve the same effect as the conventional control under the simplified hardware condition.This nonlinear modeling method lays the theoretical basis for the next DTC strategy reasearch.3.As the traditional control strategies are difficult to suppress the torque ripple of the SSRM,the DTC strategy is used to further suppress the torque ripple of the SSRM.The basic principles and main modules of DTC strategy are introduced,including the flux linkage calculation,sector judgment,flux linkage and torque adjustment,and switch table modules.Moreover,the strategy is compared with the chopped current control(CCC)strategy in detail,including the flux linkage,current,rotate speed and torque characteristics.The comparison results show that the DTC strategy significantly reduces the torque ripple of the SSRM compared to the CCC strategy.4.In order to test the effectiveness of the prototype,the static experiment bench of the SSRM was constructed and the corresponding static experiment was carried out,mainly including the inductance and torque characteristics of the SSRM.Based on the dSPACE rapid control prototype development platform,the transient experiment bench of the SSRM was constructed and the corresponding transient experiment was made for verifiction,including the nonlinear modeling method and DTC strategy.The experimental results verify the feasibility and effectiveness of the nonlinear modeling method and DTC strategy theory.