Research On Anti-disturbance Strategies For Permanent Magnet Drive System Based On Electric Vehicle Application

Because of the advantages of simple structure,high efficiency and high power density,permanent magnet synchronous machine(PMSM)has been widely used in the fields of electric vehicles,robots,aerospace,and so on.With the development of power electronics technology and control theory,PMSM drive system is becoming a hot branch of ac machine field.With the characteristics of strong coupling,multi-variables and nonlinear,the performance of PMSM drive system is effected by various disturbances.In order to acquire super drive performance and high-reliability in the complex working environment of the electric vehicle application,it is necessary to solve these problems,such as the parameter mismatch and external disturbance.First,the PMSM model and its vector control theory are proposed in this paper.Then,the parameters design process of speed and current controllers,as well as the current decoupling control method are introduced.Combing the sliding mode control(SMC)theory with motion equation,a sliding mode speed controller is designed to enhance the dynamic performance.And the contradiction between the convergence law and the chattering in the traditional sliding mode is analyzed.Some potential solutions for the problem,advanced sliding variables,optimal switching functions and new approach law-based controllers are proposed.Then,the second-order motion model of PMSM is derived.Based on the model,the non-singular terminal sliding mode controller and super-twisting controller are designed to improve the dynamic response and steady-state precision of the PMSM drive system.Secondly,the disturbances of PMSM system,such as modeling error and parameter uncertainty,inverter nonlinearity and external disturbance are analyzed.Thereby,the motor dynamics are divided into two parts: the ideal model and the uncertain disturbance.Considering the disturbance as the extended state,on basis of the ideal mode,the disturbance observer is constructed.The observed disturbance is compensated to the controller,so the robustness of drive system is greatly improved.In this paper,the proposed disturbance observers include,the motion equation-based first-order sliding mode disturbance observer,the second-order speed model-based high-order sliding mode observer,the differentiator(applied to the speed and the current loops),and the uncertainty and disturbance estimator.Finally,the design process,stability proof and result are given too.The rotor position and speed estimation method of PMSM is also studied in this paper.Firstly,the the shortcomings of the traditional extended back electro-motive force(EMF)sliding mode observer,i.e.chattering and phase shift are analyzed.Then,combining the high-order sliding mode,notch filter and phase-locked loop,a new position sensorless control strategy is proposed in this paper.Based on the new observation method,the accuracy of the rotor position and speed observation is improved.Lastly,the application limitings of conventional rotor flux observers,such as the dc offset and saturation effect of the first-order integrator,the amplitude attenuation and phase shift of low-pass filter,are analyzed.Based on generalized integrator,the second-order generalized integral flux observer(SOGIFO)and high-order generalized integral flux observer(HOGIFO)are proposed to overcome the problems.In particular,the HOGIFO has a strong suppression ability aganist the dc component and harmonics.Then,the observation of the rotor flux can be accurately obtained.Meanwhile,the PMSM sensorless control strategy can used in a wide speed range.Finally,the detailed theoretical analysis,simulations and experimental verifications are proposed.