Research On Current Segmented Optimization Control Strategy For Permanent Magnet Synchronous Motor Used In Electric Vehicle

The electric vehicle used permanent magnet synchronous motor must meet the requirements such as wide speed variation range, good torque output ability and high reliability and operational efficiency, for motors which have been well designed, the control algorithm with high efficiency is the key factor to improve the performance of the controlled motor. The permanent magnet synchronous motor can be regarded as a complex system with various variables, nonlinear and strong coupling, the parameters often changes with the variation of operational conditions, it is sensitive to the vibration and outside interference, the controller can also be regarded as a complex system coupled with electricity with high voltage and low voltage, it is not only with power devices of high voltage and high current and also includes processors with small signal inputs and integrated chips which are sensitive to electromagnetic radiation, besides, the vehicle used condition has a relative high requirement for deal, waterproof, oil resistance and anti-seismic, recently, with the emerging of more and more fierce pollution and the serve shortage of oil resource which forced people to find breakthroughs in new energy vehicles thus the research on permanent magnet synchronous motor and its driving control algorithms is of a great significance.The maximum torque per ampere is a interior permanent magnet synchronous motor common used method when it functions at low speed, it can effectively take advantage of the reluctance torque generated by the asymmetry inductance thus to enhance the torque output ability. In this dissertation, the core idea of maximum torque per ampere and its implementation method are explained. And then the likely happened issues during practical utilizations are analyzed and the corresponding solutions are proposed as well. First and foremost, the maximum torque per ampere is a high order and coupled equations based function, several approximately measured points are obtained to approach the ideal function, for the conventional control systems which adopted the liner modulator, if the control target is not capable of decoupling accurately, thus it will be hard to achieve the individual control, hence it will jeopardize the control performance; the trajectory of maximum torque per ampere is the ideal trajectory, it refers to the curve which is generated under no outside interferences according to the motor designing itself, inaccuracy trajectory will always happen under the practical function due to various kinds of interferences, thus the high performance functionality is hard to guarantee and waste may occur. An accurate decoupling algorithm is proposed in this paper, a prelinear decoupling method is proposed, one intermediate variable is used for the current decoupling of the motor which brings about a great benefit for the controller performance adjustment, based on the analysis on anti-interference ability of the conventional algorithm, a dynamic realization method based on minimum value seek is proposed, it regards the interference as a whole and try to find the minimum point of torque divided by current, it can be beneficial for the system dynamic performance improvement and convenient for the simplified designing of the regulator, thus will improve the current adjustment quality.High speed running is often required in electric vehicle used motors, thus the stable function of motor under large range of speed is often required. Fluxweakening control is an effective way to improve the PMSM functional speed, by the adoption of this control method, the motor speed can be can be gradually improved while with proper loading ability. The current trajectory control method within the traditional flux weakening region is explained in this paper, an algorithm which can extend the portion flux weakening region is proposed, this algorithm can improve the motor power density within flux weakening region; aimed at the commonly happened regulator saturation problem during high speed region, the voltage order regulating algorithm is added in to realize the real-time voltage regulation and to avoid the mistakes which may caused by processor recognition problems when the voltage order exceeds the vector range; the overmodulation method is adopted in deep flux weakening region in order to take full advantage of the DC voltage which further improve the motor speed; what’s more, the current trajectory movement issues under motor saturation and out of control are also analyzed in this paper, the reasons caused the saturation of the regulator are elaborated and the corresponding resolutions are explained.The simulation and experiment of the proposed current control method within all speed range is conducted in this dissertation, the simulation model and experimental platform are set up. All test results indicate that the proposed algorithm can meet predicted goal, it can confine the current vector to run within optimum trajectory; with a preferable dynamic and steady-state characteristics, while ensuring maximum voltage untility ratio it can effectively reduce the losing control phenomenon caused by regulators’ saturation, which can guarantee the motor a high efficiency and stable operation within all speed range. The proposed method is of good portability, being proven by experiments, as well as the theory and practice significance.