| Compared with the traditional driving method"rotating motor+roller screw",the permanent magnet synchronous linear motor(PMSLM)eliminates the mechanical conversion structure and adopts the method of directly driving sports equipment,which having the advantages of low inertia,long travel,high efficiency,fast response speed,etc.The control system with PMSLM as the core is widely used in high-precision manufacturing industries such as laser cutting and additive manufacturing.However,during the operation of PMSLM,due to the existence of the inverter dead zone effect and the influence of nonlinear factors such as tube voltage drop when the power electronic device is turned on,there will be a series of harmonic components in the linear motor control system.These harmonic components will cause additional losses in PMSLM,resulting in a rise in the temperature of the three-phase winding of PMSLM,reducing the working efficiency.At the same time,the current harmonics will produce thrust fluctuations,which directly reduces the reliability and stability of the PMSLM control system and severely restricts the application of PMSLM in high-precision occasions.Therefore,this paper proposes an adaptive harmonic injection method to suppress the current harmonics of PMSLM.This paper specifically includes the following aspects of research:1. Firstly,the basic structure and working principle of the permanent magnet synchronous linear motor are analyzed,and the mathematical model of PMSLM under three coordinate systems are established in accordance with the principle of coordinate transformation.Then the principle of space vector pulse width modulation(SVPWM)technology is studied,and the technology is simulated and verified.Finally,analyzing and comparing several common vector control methods.Combined with PMSLM's mathematical model and SVPWM technology,the i_d=0 vector control method is used to build a PMSLM three closed-loop vector control system in Simulink.2. Analyzing the generation of harmonics caused by the air gap magnetic field distortion,inverter dead zone effect and turn-on voltage of power electronic device,establishing the mathematical model of the harmonic components and the harmonic steady-state voltage equation.The harmonic injection method is introduced to construct a harmonic suppression loop to suppress the main harmonic components.Firstly,the harmonic component in the dq coordinate system is extracted,then the harmonic component is zero as the control target,and the harmonic compensation voltage is obtained through the harmonic steady-state voltage equation.Finally,the harmonic compensation voltage is positively fed back to the SVPWM reference modulation voltage terminal,which cancels each other with the harmonic components to achieve the effect of suppressing harmonics.Finally,a PMSLM harmonic suppression vector control system based on harmonic injection method was built in Simulink,and the effect of harmonic suppression was verified by simulation.3. During the operation of PMSLM,the values of inductance,resistance,and flux in the motor will change in real time,and it will affect the accuracy of harmonic suppression by harmonic injection.Therefore,in order to improve the accuracy of harmonic suppression and reduce the impact of parameter disturbance on harmonic suppression,this paper introduces the model reference adaptive parameter identification(MRAI)algorithm,which together with the harmonic injection method constitutes the adaptive harmonic injection method.Among them,MRAI can online identify the inductance,resistance and flux value of the motor during operation,and feed back the identification results to the harmonic suppression link to suppress current harmonics in real time and improve the accuracy of harmonic suppression.First introducing the basic structure and principle of MRAI,then determining the reference model and simulation model,and using Popov super-stability theory to establish the parameter adaptation rate.Finally,building an adaptive harmonic suppression loop in Simulink,change the motor parameters,and verifying that the parameter identification is effective and the effectiveness of harmonic suppression under parameter disturbances.4. Based on the AD5435 semi-physical simulation system,an experimental control platform was built,and the adaptive harmonic injection method used in this paper was experimentally verified under different experimental conditions.The verification results show that the adaptive harmonic injection method used in this subject can effectively suppress the current harmonics and reduce thrust fluctuations.Moreover,the influence of the disturbance of the motor parameters on the harmonic suppression effect can be reduced,and the accuracy of harmonic suppression can be improved. |
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