Research On The Flux Weakening Control Strategy Of Premanent Magnet Synchronous Motor Via Improved Projection Method With Improving Parameter Robustness

When the voltage on the supply side of the motor is limited,the flux weakening control can effectively extend the speed range of the motor.The dynamic performance of permanent magnet synchronous motor flux weakening control based on online search method is good,which is convenient to design the given trajectory of the quadrature and direct axis current under flux weakening conditions,and is conducive to real-time online application.Most of the online search methods use algebraic methods for online iterative solution,the projection method for flux weakening control utilizes geometric projection for iteration,which can effectively reduce the number of iterations and the computational burden of the controller compared to other algebraic methods.However,the iterative initial point position of the projection method is relatively fixed,and this positioning method of the initial current point increases the number of iterations when the target point is far from the initial point,which will cause unnecessary computational burden.At the same time,the iterative process of the projection method depends on the motor parameters.The infl uence of various factors such as temperature,magnetic saturation,and vibration can cause changes in the motor parameters,thereby affecting the given quadrature direct axis current under flux weakening conditions,ultimately leading to a deterioration of the system’s flux weakening performance.Therefore,it is of great significance to conduct research on the projection method for flux weakening control strategy for permanent magnet synchronous motors in response to the above issues.This thesis takes the surface mounted permanent magnet synchronous motor as the research object.Firstly,an improved projection flux weakening control strategy is studied for the iterative initial point positioning problem in projection method flux weakening control.This strategy designs different current iteration initial point positioning methods in the acceleration stage and steady-state stage of flux weakening,in order to achieve dynamic tracking of the current iteration initial point to the target point,avoiding multiple iterations caused by the distance between the initial point and the target point and reducing the computational burden of the controller.Secondly,in response to the problem of poor system parameter robustness caused by reliance on motor parameters during the iterative process,this thesis studies an improved projection method flux weakening control strategy with improving parameter robustness.This strategy uses a Luenberger disturbance observer to simultaneously observe voltage disturbances caused by changes in multiple motor parameters,and compensates the observed lumped voltage disturbances in real-time to the voltage limit circle equation to achieve dynamic updates of the voltage limit circle,thereby providing the optimal current operating point in the case of motor parameter mismatch and improving the system’s parameter robustness.Thirdly,in order to demonstrate the feasibility and effectiveness of the improved projection method flux weakening control strategy and the improved projection method flux weakening control strategy for parameter robustness improvement studied in this article,simulation and experimental verifications were conducted on the studied strategies.The simulation and experimental results show that the improved projection method flux weakening control strategy can effectively lessen the excessive number of iterations caused by the initial point being far from the target point,shorten the iteration time,and reduce the operational burden of the controller.Compared with the improved projection method flux weakening control strategy,the improved projection method flux weakening control strategy with improving parameter robustness can effectively reduce the system’s dependence on stator inductance and permanent magnet flux parameters under flux weakening conditions,and exhibit better flux weakening operation ability in the case of motor parameter mismatch.