Research On Design And Parameters Of PMSM For Electric Passenger Cars

In order to alleviate the energy shortage and environmental pollution problems, pure electric vehicles has become an important development direction in today’s automobile industry. As a special traction motor for the primary power delivery of pure electric vehicles,, Interior Permanent Magnet Synchronous Motor(IPMSM) has become a hot research field of the traction motor by the merits of small size, light weight, high efficiency, high output power density, high torque current ratio, and the wide range of field-weakening. Actually, for high-power traction IPMSM control the key is to solve a small denominators control problem. A small parameter deviation will directly affect the precision of the high-power traction IPMSM.The difficulties of driving motor research lie in the output performance of high-power IPMSM in actual traction, design, the quantitative study of parameters. The cores of precise quantitative study are the design and parameter calculation of IPMSM for electric buses. From the character requirement and control performance demand, taking the pure electric bus as the background, this dissertation conducted in-depth research on the following points: the parameter matching design of high-power tracking IPMSM, the impacting mechanism of the motor parameter to the control performance, the structural parameter design method, the traction motor design to meet the driving demand, the calculation and experimental methods of key control parameters, the system experimental validation, etc.1. The output performance of pure electric vehicle drive by IPMSM has great difference with that of traditional combustion engine. The superiority of the pure electric vehicle is determined not only by the performance of its core components, but also greatly depending on the coordination between the components. From the dynamics of the vehicle, this dissertation give the evaluating criterion of electric vehicle power and the constraint model of the key performace parameters. A mathing design method of electric vehicle IPMSM performance parameters is proposed. That lays the ground work for the IPMSM design of pure electric vehicle drive to meet specific requirements, and provides the precondition for the parameter matching and performance optimization of the electric vehicle.2. As the performance of control is influenced greatly with the change of the traction IPMSM parameters, the fundamental wave vector method is adopted by the definition of per unit in this paper, and the performance of control influence mechanism for the traction IPMSM parameters in different control strategies are analyzed in-depth. And then the design method of the traction IPMSM by increasing quadrature axis inductance parameter is proposed. This method for pure electric bus cars can satisfy the requirements of high torque output at low speed as well as the wide range of field-weakening at high speed. The design method of increasing quadrature axis inductance parameter provides a theoretical basis for the high-power traction IPMSM rotor structure optimization design.3. Aimed at the significant differences between the design method of the traction IPMSM and ordinary fixed frequency sine wave PMSM, all kinds of special requirements and design principles of the traction IPMSM for pure electric vehicles are analyzed systematically. On the basis of the performance parameters of the matching design and vehicle arrangement space constraints, the analytical determination of optimal split ratio to meet the maximum torque density for traction motor is proposed, and the size precision scope of the traction IPMSM stator structure for pure electric bus, and the rotor structure of the traction IPMSM is determined by the increasing quadrature axis inductance parameter rotor optimization design method. Finally the electromagnetic performance of the designed prototype is calculated by FEM. The effectiveness of the proposed design method of traction IPMSM is proved by the prototype experiments.4. Aimed at the research object of the traction IPMSM in the paper, the rotor structure without damping conducting cage bar, the traction IPMSM itself has no line-starting ability leading to the finite element calculation with load starting being difficult for the structural traction IPMSM. increasing the difficulty of forecasting performance and the accurate calculation of the control parameters under different load conditions. A method to determine the rotor initial position in load operation is proposed in this paper. The motor power-angle characteristic curve of the traction IPMSM is determines by this method, and the rotor position in the actual starting moment of the traction IPMSM is calculated. Therefore, the finite element calculation with load starting of the traction IPMSM is realized, and the necessary premise is provided for the prototype performance forecasting and the d- and q-axis inductance parameters of accurate calculation.5. As the calculation difficulties of d- and q-axis inductance parameters high-power IPMSM and the experimental test, based on the analysis and derivation of the mathematical model of self-inductance and mutual inductance coefficients, the internal mechanism of ignored cross-saturation effects of static finite element method and cross-saturation magnetic permeability considering the impact of the freezing are studied intensively. To to meet the real pure electric vehicle drive power IPMSM control parameter changing needs, a freezing orthogonal axis inductance permeability method is proposed. Based on the precisely calculation of magnetic field saturation under load situation, two different finite element methods are used to calculate the d- and q- axis inductance at differenet load circumstances, and prototype perpendicular axis inductance parameters are experimentally measured by static exchange method. Through the comparative study of the experimental data and two finit element ehtod, measured values and the calculation of ignored the static prototype cross-saturation effect of static finite element agree well. But the results freeze permeability are closer to d- and q- axis inductance parameter values of at different load points. Thus, providing a more accurate d- and q- axis inductance calculation method for the pure electric vehicle control system tests and simulation.6. Based on the control system design using DSP, and the prototype control system experimental platform is built in this dissertation. The core issues such as the control parameters, load performance, field-weakening performance of the high-power traction IPMSM are tested experimentally. The calculation by the proposed method agrees well with the experimental data. It shows that the designed prototype can meet the requirements of the performance demand. Moreover, the proposed design method of driving IPMSM and the parameter calculation method are validated.