Research On Key Technologies Of High Power Permanent Magnet Synchronous Motor Servo Control System

In recent years,high-power permanent magnet synchronous motor(PMSM)servo system gradually replaces the existing hydraulic servo structures and products with its high precision,high power density,fast frequency response and low noise?It is used in servo systems such as stamping,cutting and metal forming.And its applications cover many aspects needed for the rapid development of national economy and national defense construction,such as aerospace,rail transit,heavy equipment and so on.Although the technical level and market share of domestic brands in low-power universal servo system are constantly improving,there is still a big gap between domestic and foreign brands in high-power servo system.The improvement of power level and the deterioration of application conditions bring new technical difficulties to the high-power servo drive system.Although the system focuses on different performance indicators under different special application background,the system faces some common problems,such that,the current dynamic response is severely limited by controller saturation and bus voltage,the discretization error and the dq-axis coupling affect current tracking performance at low switching frequency,the robustness of speed control is limited by controller saturation and dynamic performance,the effect of restraining periodic speed fluctuation and external load is poor at low speed and so on.Aiming at the above problems,this paper studies the key technologies of current and speed control of high-power PMSM servo system,which provides new control strategies and practical exploration for the development of domestic high-power servo drive products with higher performance.In this paper,firstly,the disturbance and parameter perturbation in the system are analyzed,and the model of PMSM with disturbance in different coordinate system is built.Then,the differential voltage equation in the stationary two-phase coordinate system(??-axis)is solved,and the accurate electrical model is obtained.Then,the mechanism of periodic speed fluctuation in the system is studied,and the impact of current sampling errors is analyzed using the complex vector method.The modeling and analysis provide the basis for the controller design.In order to improve the dynamic performance of current control under large current command and voltage limiting,deadbeat predictive current control(DPCC)and finite control set model predictive control(FCS-MPC)are studied in this paper.In the current plane,geometric method is used to judge the relative position of current command and working point.The current tracking dynamic is effectively improved by tracking the nearest working point to the current command in each cycle.In order to improve the robustness of the model-based current control method,a disturbance observer based on the moving horizon optimization theory is designed to observe and compensate the voltage error caused by parameter mismatch.Furthermore,an improved DPCC structure based on the accurate model of??-axis is used to reduce the dq-axis coupling and system delay,which improves the model accuracy and the current control performance at low switching frequency.Experimental results validate the generality of the proposed current control methods and the effectiveness of the composite current control strategy.In order to improve the ability of speed control of high-power servo system to atten-uate external load disturbance and parameter perturbation,this paper firstly studies the permanent magnet synchronous motor H_?speed control.The parameter tuning method of the weighting function are studied.Compared with proportional integral(PI)controller,The solved H_?speed controller has better anti-disturbance ability when the dynamic performance is similar.In order to further improve the disturbance rejection ability and dynamic performance of the mechanical system,the structure of the H_?speed control sys-tem is improved.The disturbance observer,feedback controller and feedforward controller are designed step by step.Accurate observation of external disturbance and two degree of freedom H_?control,velocity feedback closed loop are realized.The closed-loop transfer function of the system is derived.The theoretical analysis and experimental compari-son show that the proposed method can effectively improve the dynamic characteristics,anti-disturbance ability and inertia robustness of the speed control.Although the proposed H_?speed control can effectively suppress external distur-bances,the suppression effect of periodic speed fluctuations needs to be improved.In this paper,an iterative learning control(ILC)parallel structure with forgetting factor is used to suppress periodic speed fluctuation and external load disturbance.Firstly,taking PI parallel speed controller as an example,the open-loop frequency domain expression of the whole structure is derived accurately,and a stability analysis method of parallel structure based on Nyquist stability criterion is proposed.The expressions of ILC control parameters are solved to obtain the stable range,and the parameter tuning method is pro-posed.The position sampling mechanism is designed enabling the algorithm to operate at different speeds.In order to suppress the influence of non periodic disturbance and noise in the actual situation,the method of embedding zero phase filter in ILC is studied.Furthermore,the parallelled PI speed controller is replaced by 2-DOF H_?speed controller and the hybrid strategy is verified by experiments.Then the iteration period is extended for the external periodic load.Experimental results show that the proposed method can more suppress the inherent periodic speed fluctuation and periodic external load in the system effectively.