Research On Sensorless Control Technology Of Permanent Magnet Synchronous Motor For Electric Vehicles

To cope with the impact of global environment and climate change on human existence,governments at home and abroad have been advocating energy restructuring and actively developing and utilizing clean energy to reduce greenhouse gas emissions for decades.China put forward the development strategy goal of "carbon neutral" and "carbon peak",and various industries are continuously implementing the development concept of low carbon and environmental protection while continuously promoting sustainable economic development.Among them,the automotive industry as China’s leading force in the development of a lowcarbon economy,major automobile manufacturers are carrying out the development and production of new energy vehicles.The permanent magnet synchronous motor is the first choice for electric vehicle drive motor because of its high power density,wide speed range,excellent starting and speed regulation performance,which meets the working environment of frequent start/stop and high torque at low speed required for electric vehicles.Due to the complex and changing working environment,the mechanical sensor in the traditional speed control system to detect the position of the motor rotor is easily damaged,so the sensorless technology is of practical significance to improve the safe and reliable operation of electric vehicles.This thesis first analyzes the current situation of electric vehicle and drive motor control technology research,and establishes the main research content of this paper.Then the structure and electrical characteristics of permanent magnet synchronous motor are introduced,and the mathematical model of permanent magnet synchronous motor is established through coordinate transformation theory.Several commonly used vector control methods are analyzed and compared,and the SVPWM technology is explained in detail.Then,for the problem of how to determine the parameters of the speed regulator and current regulator in the vector control system,an improved particle swarm algorithm is proposed for the self-tuning of PI parameters.Based on the basic particle swarm algorithm,the speed evolution equation is divided into two parts of the self-factor and the social-factor,and the optimization process of the particle swarm algorithm is optimized by applying different linear functions to these two parts.The optimization process of the particle swarm algorithm is optimized by applying different linear functions to these two components.By building a simulation model of the vector control system of a permanent magnet synchronous motor,the feasibility of the self-tuning PI controller parameters of the particle swarm algorithm is verified,and it is demonstrated that the improved particle swarm algorithm takes less time and has higher accuracy in the optimization search.Next,a sensorless technique based on a sliding-mode observer is proposed to obtain rotor information for a sensorless technique in which the motor rotor position information is susceptible to external disturbances and changes in its own parameters.The fundamental theory of the sliding mode control is detailed,and the jitter problem inherent to this control method is also regarded,which can be improved from the following two aspects by analysis.The first is the use of an exponential convergence law to weaken the jitter,and the use of a double inverse tangent function instead of the traditional sign function to further weaken the jitter.Second,a phase-locked loop-based position observer is used for estimating rotor information.The simulation model of the system before and after the improvement is established,and the simulation is combined with the actual operating situation of the electric vehicle,and the results demonstrate that the improved sliding mode observer can not only effectively weaken the jitter,but also can better predict the speed and position information of the motor.Finally,the sensorless technique of pulsed high-frequency voltage injection method is used to get rotor information for the problem of sliding mode observer method that causes ineffective due to low counter-electromotive force when the motor is in zero-speed and lowspeed operations.The saturated convex pole of the hidden-pole motor is emphasized,and the basic principle of voltage injection is explained.The correlation simulation model is established to verify the usefulness of the method in the low speed condition.