Research On Flux-Weakening Control Strategy Of Permanent Magnet Synchronous Motor

In the energy-short world,permanent magnet synchronous motors have been widely used in many fields due to their advantages of high efficiency,low energy consumption,high power density,and small size.The flux-weakening control can broaden the speed range of permanent magnet synchronous motor to meet the needs of different applications.It has become one of the research hotspots in the field of electric drive today.This paper focuses on how to expand the operating speed range of the permanent magnet synchronous motor through different flux-weakening control strategies and improve the flux-weakening performance of the system.This paper introduces the structural characteristics of permanent magnet synchronous motor and establishes a mathematical model,expounds the principle and control strategy of field orientation control,studies the constraint conditions and operating region of flux-weakening control,analyzes the realization of SVPWM algorithm and validates it through simulation.These lay a theoretical foundation for the study of the flux-weakening control strategy.In order to meet the performance requirements of constant power control and wide speed range operation for many application scenarios of permanent magnet synchronous motors,the principle of flux-weakening control of permanent magnet synchronous motor is described,the influence of motor parameters on the flux-weakening performance is studied,and a permanent magnet synchronous motor flux-weakening control system based on voltage closed-loop feedback is constructed.The maximum torque per ampere control is used in the constant torque region to improve the system operation efficiency.The voltage closed-loop feedback flux-weakening control is used in the constant power region.By comparing the relationship between the reference voltage and the output limit voltage of the inverter,it is automatically judged whether to enter the flux-weakening region,and the output d-axis demagnetization current automatically adjusts the excitation level and expands the speed range of the system's constant power region.A simulation model of voltage closed-loop feedback flux-weakening control system is built.Simulation experiments show that the control scheme achieves a wide range of flux-weakening acceleration and the smooth transition from constant torque region to constant power region.To solve the problem of out-of-control of current oscillation,torque oscillation and the saturation of current regulator in deep field weakening region of voltage closed-loop feedback flux-weakening control system,a new type of deep flux-weakening control strategy is proposed.The q-axis current error integral control slows down the rate of change of the q-axis current and suppresses the current regulator saturation.Then limit the d-axis current according to the maximum torque per voltage curve,determine the q-axis current increment and re-planning the flux-weakening current trajectory.Designing the parameter self-tuning fuzzy PI regulator on the current loop to further suppress current oscillations and torque oscillations in the deep field weakening region.A simulation model of new deep flux-weakening control system is built.The simulation experiment shows that under the new deep flux-weakening control strategy,the system operates stably in the deep flux-weakening region,the current oscillation,torque oscillation and saturation of the current regulator are obviously suppressed.The smooth transition of the different operating areas in the whole speed range and the smooth switching of the three phase control strategy are realized,and the dynamic performance of the system is good under continuous load mutation.