Research On Flux-Weakening Control Strategy For High-Speed Permanent Magnet Synchronous Motor Based On Active Disturbance Rejection

High-speed PMSM has the advantages of small volume,high power density,small inertia and good dynamic characteristics,which is widely used in electric vehicles,high speed machine tools,flywheel energy storage and other industries.However,due to the large harmonic current and high mechanical loss at high speed,the motor will generate serious heat,which will change the actual parameters of the motor and affect the control performance.Moreover,the high-speed motor drive system under low load-frequency ratio has serious magnetic chain and torque coupling under high speed conditions,which will increase the coupling of the current loop and affect the dq axis voltage distribution,and also reduce the control performance of the motor.Therefore,it is necessary to study the parameters identification algorithm of the motor to feed back the actual parameters to the control algorithm,and optimize the voltage distribution of the motor under the high-speed flux-weakening condition to improve the control performance of the motor.At the same time,it is necessary to consider the uncertain disturbance problem of high speed PMSM in practical application scenarios,and improve its robustness by disturbance rejection control.In this paper,aiming at the above problems and requirements,the high-speed PMSM flux-weakening control drive system is studied in the following aspects :1.The mathematical model of PMSM in dq coordinate system and the implementation method of vector control are described in detail.Combined with the voltage limit circle,current limit circle,MTPA curve and MTPV curve,the running track of PMSM in the flux-weakening region is analyzed.The running track of PMSM is divided into base speed,flux-weakening region I and flux-weakening region II,and the current distribution method of the corresponding working area is introduced.In this paper,the flux-weakening control strategy based on dq-axis voltage feedback is adopted.In view of the voltage distribution problem caused by the coupling of dual current regulators in the high-speed region of flux-weakening,the control performance is improved by using a single current regulator,and the smooth switching between PMSM and flux-weakening conditions below the base speed can be realized.Simulation and experimental results show that the single current regulator flux weakening control strategy can make the motor have better steady state performance and can switch smoothly between MTPA and flux weakening control.2.Aiming at the problem of parameters variation,based on the SQCR-VVA control method used in this paper,the error between the voltage and current given value and the actual value when the motor parameters are not matched with the parameters used in the controller is analyzed,and the mathematical relationship between the parameter variation coefficient and the above error is obtained.Then,the actual parameters calculated are fed back to the control strategy online at the same time through the parameter compensation module.The control objective of online compensation for multiple PMSM parameters is realized,and the control performance of the motor is improved when the parameters change.The effectiveness of the parameter compensation algorithm is verified in the experimental platform.When the inductance and flux are changed by 30% and 5% respectively,the recognition error of the parameter compensation algorithm for the two parameters is less than 5 %,and the torque error is reduced from 12.02 % to 0.38 %.3.In order to further improve the robustness of the flux-weakening operation of PMSM,the ADRC controller is selected to replace the PI controller in the speed loop.Firstly,the basic principle and implementation method of ADRC are analyzed,but it contains multiple nonlinear functions,which leads to more parameters to be set and higher setting difficulty.Therefore,linear function is used to replace the nonlinear function,namely LADRC,which reduces the number of parameters to be set and the difficulty of setting.According to the motion equation of PMSM,the first-order LADRC controller for the speed loop of motor vector control is designed,and the parameters of the controller are determined by the idea of bandwidth.For the problem that the input signal with high tracking frequency of LTD has phase difference,a phase compensator is designed based on the first-order LPF and HPF,so that it can better track the constant input signal and the input signal with high frequency.Through the simulation and experimental results,it can be found that,compared with PI control,LADRC control method can make the motor stably track the given speed without overshoot in the speed regulation process.When the PMSM works in a stable state,the speed,torque and current also fluctuate.