The Research Of Sensorless Vector Control Strategy Of Permanent Magnet Synchronous Motor For Electric Vehicle

Environmental pollution and energy shortages are important aspects in the world, This articles presents that the development of new energy vehicles are the main means to solve the above problems and that motor driving system is the most important part of new energy electric vehicles. Permanent magnet synchronous motor (PMSM) is the first choice of a modern electric vehicle motor driving system because of its efficient power density, high operating efficiency, compact and smaller in size, etc. There is always a sensor assembly at the side of the PMSM shaft to get the motor speed and the rotor position. Because of operating conditions and motor operating environment, the PMSM become relatively poor in performance, which greatly increases the post-maintenance costs of electric vehicles, and affects motor vehicle stability of the controlling system. Therefore, the development of sensorless vector control system has become an ideal and necessary topic today.Sensorless control technology includes open-loop and closed-loop control method, the open-loop in the case of outside interference estimation accuracy is low and inaccurate. On the other side, Closed-loop can quickly track system output, effectively weakening the noise and environmental interference. Aiming vehicle permanent magnet synchronous motor drive system features, based on the new proposed sliding mode observer (Sliding Mode Observer, SMO), high frequency injection method (High Frequency Injection, HFI) and model reference adaptive (Model Reference Adaptive System, MRAS) three position sensorless control strategy. We establish a system model based on three control strategy, simulation verify the feasibility of the three methods.Sliding Mode Controller has the advantages of simple arithmetic, very fast dynamic response in PMSM sensor less control. Based on the current error equation, designed sliding mode observer (SMO), using the arc tangent function instead of sign function to reduce the chattering. However, we collect back EMF of PMSM for the sliding mode control theory, at the motor starts and low-speed range, the back EMF is very weak and difficult to acquire. Therefore, High frequency injection (HFI) method is presented to estimate motor speed and the rotor position of PMSM for problems of SMO, in the process of high-frequency injection estimation, adding a large number of filters, resulting in declining of stability even distortion in high speed of PMSM. Finally, the combination of the two control strategies, realized to estimate the speed and position of the rotor in the full range of PMSM sensorless vector control. This method applies to vehicle drive motor which has apparent salient structure, with high estimation accuracy.When an electric vehicle uses an inconspicuous salient structure of motor, the recognition accuracy for the salient is not high enough to extract useful information and to separate useless information. Therefore, we finally proposes an estimation method for this type of motor which is model reference adaptive control (MRAS). We make the permanent magnet synchronous motor equation as the reference model and the stator current equation as adjustable model to design model reference adaptive observer, and ultimately achieving estimation of the speed and the rotor position of PMSM. Through simulation, the model reference adaptive control algorithm is simpler, easier to implement, broader in speed estimation, it also has a very good estimation accuracy in low and high speed range.