Core Losses Analysis And Real-time Magnetic Equivalent Circuit Modeling Of A Segmented SRM-BSG For Mild Hybrid Electric Vehicles

With the acceleration of urbanization,the vehicle ownership is increasing rapidly in China.The energy shortage and environmental pollution are becoming more and more prominent,and the issue of energy saving and emission reduction has been paid more attention.The belt-driven starter generator(BSG)is a mild hybrid technology,and the BSG performs well in quick start-up,quick stop and recovery braking energy,which can effectively save energy and reduce emission.Due to the small change in the structure of vehicle,the additional production cost is relatively low and the cost performance is high.Compared with the induction motor and permanent magnet motor,the switched reluctance motor(SRM)is an ideal candidate for the BSG motor,which has the simple structure,low cost,and high robustness.Furthermore,it can work in harsh environment.In this dissertation,under the financing of the National Local Joint Engineering Research Center for Hybrid Vehicle Technology,the deep study of a novel 16/10 segmented SRM(SSRM)is made,including electromagnetic characteristics,torque ripple,fault tolerance,core loss,and real-time equivalent magnetic circuit model.The main research contents are as follows:1.The basic principles and control methods of the SSRM are clarified,and the prototype structure and the size of each part of the novel SSRM are introduced.Based on the detailed parameters of the SSRM,the 3-D finite element analysis model is builded.Based on this model,the static characteristics and dynamic characteristics of the SSRM are studied,including magnetic flux density,flux linkage,inductance,static torque,dynamic torque,torque ripple torque,and fault tolerance.The comparative analysis of electromagnetic characteristics is performed by using a conventional SRM with 8/6 structure and SSRM.The simulation results show that the torque ripple of the SSRM is smaller and the output torque is larger.In the case of open-circuit of one phase,the SSRM shows good fault tolerance.In case of failure,the vehicle can still run normally and maintain stable power.2.A new nonlinear lumped parameter circuit model is presented,and the core loss of the SSRM is analyzed.The influence of magnetic saturation,leakage flux and joule loss to the core loss of the SSRM are clarified.The nonlinear core loss model with incremental leakage inductance,incremental equivalent winding resistance,incremental magnetizing inductance and incremental equivalent core loss resistance is established.Based on the new nonlinear lumped parameter circuit model,the precise calculation method of core loss for the SSRM is proposed.In the new algorithm,the incremental leakage inductance and incremental equivalent winding resistance are considered together to ensure the one-to-one relationship between them and the current.Similarly,the incremental magnetizing inductance and incremental equivalent core loss resistance are also considered together.The method lays a foundation for the optimization design,thermal analysis and precise control of the SSRM.3.Several common SRM modeling methods are introduced,and a new real-time magnetic equivalent circuit(RT-MEC)model is proposed.Based on the air gap reluctance,slot leakage reluctance and iron core reluctance,the RT-MEC model of the SSRM is established.The RT-MEC model is simplified by using the proposed model and the special structure of the SSRM,and the model is transformed into a 10-by-10 square matrix system.A new algorithm for real-time simulation analysis of the model is presented.Compared with the gauss-seidel iteration method,this method alleviates the convergence problem of iterative inversion of the matrix.Moreover,the computational burden is small and the model works steadily.The real-time simulation of this model is of great importance to build the joint simulation platform of vehicles.4.Based on the requirements of experiments,the test bench of the static characteristics and dynamic characteristics are built.The test bench is used to measure the results in term of the electromagnetic characteristics,torque ripple,fault tolerance,core loss and RT-MEC modeling,and the experimental results are compared with the simulation results.The comparison results show that the SSRM performs small torque ripple,large output torque,and good fault tolerance.Furthermore,the validity and correctness of theoretical analysis of the RT-MEC model and calculation method of core loss are verified.