Control Strategy Of Flux Intensifying Permanent Magnet Brushless Motor With Wide Speed Range For Electric Vehicles

With the deteriorating energy crisis and environmental pollution, new energy vehicles have emerged with the characteristics of energy conservation and environmental protection, resulting that lots of manpower, material and financial resources have been invested on the research and promotion. As a member of the new energy vehicles, the electric vehicles(EVs) have attracted increasing attention and enjoyed rapid development due to the advantages of low noise and no pollution. Furthermore, among the competing traction motors, the traditional interior permanent magnet brushless(IPMBL) motors have been extensively applied in EVs since they inherently offer the advantages of easy maintenance, high power density and torque density. However, it is difficult to regulate the open-circuit air-gap field produced by permanent magnets, which makes it difficult to achieve wide speed operation in the constant power range to some extent. Meanwhile, the efficiency of the motor is relatively low in high speed region. Therefore, with the rapid development of urban transportation, the traditional IPMBL motors cannot meet the drive requirements of modern EVs completely. To solve the problems, a new type of wide speed flux-intensifying permanent magnet brushless(FI-PMBL) motor is investigated in this paper. Not only the motor inherits the advantages of traditional PMBL motor, but also provides intensified flux and high efficiency. According to the nature of the FI-PMBL motor, this paper presents the corresponding control strategy. Furthermore, the theoretical analysis and experimental verification are carried out. The main research work is given as follows:Firstly, the development status of EVs and the research status of wide speed FI-PMBL motor and vector control are introduced in the paper. Next, the topology of FI-PMBL motor is shown. Moreover, the mathematical mode of FI-PMBL motor is set up in the stator coordinate, based on it, the mathematical mode of FI-PMBL motor is further deduced in the rotor coordinate.Secondly, the differences of the vector control used in the FI-PMBL and traditional PMBL motor are analyzed. Based on it, the basic principles of maximum torque per ampere(MTPA) and id=0 control are described in detail, and the control simulation model of the motor is built. After that, the different conditions, including starting, variable speed and variable load, are simulated and the corresponding results are compared, verifying the superiority of MTPA control based on the flux-intensifying characteristics.Thirdly, the components of the drive control system are introduced, where the hardware design and software design of drive control system are analyzed in detail, and the motor experiment platform is set up.Finally, the experiment platform is set up, and the experiments used MTPA and id=0 control are tested on the prototype motor, mainly including starting, variable speed and variable load. By comparing the experimental results, the superiority of MTPA control is illustrated, and the flux intensifying effect can be achieved. Therefore, the experimental results verify the correctness and feasibility of MTPA control.