Research On Key Technologies For Control Of Permanent Magnet Synchronous Motor Connected With LC Filter

At present,almost all the PMSM controllers use PWM technique.In the applications of long-distance transmission lines,such as drilling platform and seabed exploration,PWM waves will cause high reflection effect in transmission lines,which may burn out the motors in severe case.Installing LC filter between the inverter and motor is a simple and effective method to suppress the reflection effect.Nevertheless,some shortcomings exist in the PMSM control systems with LC filters.The characters of the zero-state response are changed by the LC filter,so relatively larger error may be engendered or even failure in the process of initial position identification based on the voltage pulse injection.The model of the drive system is changed by the filter.The performance of the system will be limited if the conventional 2-closed-loop control method is used.Larger error or unconvergence may be caused in conventional model-based sensorless control and fault diagnostic methods of drive system.The known solutions are complicated or high-cost,etc.This dissertation devotes to solving those shortcomings.Starting with the system model,this dissertation studies identification of initial position,control of the drive system,sensorless control,fault diagnosis and fault-tolerance control of the drive system.The four main contents are listed as following.The estimation of the initial position is studied to resolve the issue that conventional voltage pulse injection methods are highly inaccurate or even fail.If the pulsed voltages are injected,the current response of the drive systems with LC filters must be seen as the response of a 3-order system.Higher harmonics are included in the current responses.Thus,the larger error may exist when the conventional voltage injection method is still implemented.The error problem is analyzed,and the transfer function of the equivalent circuit is deduced,and it is proved that the expression of the low-order component approaches the situation when the LC filter is not connected.Thus,the function-fitting-based identification of initial position strategy is proposed.The step responses of the current vectors are filtered by the 2-order Butterworth filter,and the function fitting for the filtered data is used.The inductance is estimated by the time constant,thus the position being estimated.The larger error even false detection is resolved.The effectiveness of the proposed estimation method of initial position is verified by simulation and experimental results.The effectiveness of the proposed initial position estimation strategy is verified by the experimental results.In order to improve the transient performance of the system,the sliding mode vector control considering the LC filter is studied to improve the control performance.The conventional 2-closed-loop control scheme does not control the LC filter,so the control performance will be worse.The mathematical model is deduced,and the reaching-law-based sliding mode controller for LC filter and PMSM is proposed.Every closed-loop control law is deduced.The issue that the control performance becomes worse caused by LC filter is solved.The design method of the parameters is discussed.The comparison between cascade PI control and the proposed sliding mode control is realized by simulation and experimental tests,and the advancement of the proposed sliding mode control strategy is verified.In order to solve the possible large error or even unconvergence caused by conventional methods based on the observers because of the LC filter,the issues of sensorless estimation are studied.Because the mathematical model is changed by the LC filter,the voltages and currents in the filter output and motor input are different.Therefore,the conventional observer methods based on the models may be invalid.The full-order PI observer and full-order sliding mode observer are proposed.The design of the gain matrix is studied.The issues of conventional observers are resolved.On this basis,the compound control of low-speed PLL and quadrature PLL is presented.In intermediate region,the result is fused by two PLLs through root mean square method according to the quadrature PLL and low-speed PLL,thus improving the performance of the sensorless control in this region.Lastly.The proposed strategies are demonstrated by simulation and experimental results.The open-circuit fault diagnostic and fault-tolerance method for the inverter and capacitance branches are studied to resolve the possible error or even unconvergence of the conventional methods for drive system caused by the LC filter,and the issue that capacitors breaking down.The model of the system is changed.The fault diagnostic methods based on the fault observers should be revised because the fault observer is based on the model.The fault observer is presented.Thus,with the help of the constructed observer,the fault signatures are deduced,and the open-circuit fault diagnostic method based on the residual errors of the voltages are presented.The faults are extracted from the least square regression method.The open-circuit fault diagnosis for the capacitor branches of LC filter based on the absolute mean currents is proposed,and the fault signatures are deduced.Based on the previous studies,the fault-tolerant topology of three-phase four-switch is revised for the fault-tolerance control of the PMSM with LC filter,and the effect of the LC filter is analyzed.The effectiveness of the methods is demonstrated by simulation and experimental resuts,therefore realizing the fault diagnosis and fault-tolerant control of PMSM drive system with LC output filter.