| Permanent Magnet Synchronous Motor(PMSM)has broad application prospects in modern advanced industrial fields such as electric vehicle drive,locomotive traction and aviation propulsion.The variable frequency speed regulating device has become one of the drive circuits widely used in AC synchronous motor because of the advantages of various speed regulating methods,accurate speed regulating and energy saving.However,due to the non-linear factors such as the inverter dead time of the frequency conversion device and the tube voltage drop,as well as the distortion of the air gap magnetic field caused by the design process of the motor itself,the motor current contains rich harmonic current components.In addition,the vibration and noise generated by each harmonic current component of the motor has a great influence on the operation performance of the motor,which will seriously limit the application of PMSM in the field with higher requirements on the performance of the motor.Therefore,based on the analysis of the source of the harmonic current of the motor,the design of a frequency conversion system that actively suppresses the current harmonic is of very important research significance for improving the performance and efficiency of the motor’s overall operating system.Firstly,according to the structure of PMSM system and the principle of variable frequency speed regulation system,the ideal mathematical model of the motor is established.Due to the non-linear factors of the inverter switch tube and the non-sinusoidal air gap magnetic field,the voltage and current harmonic content generated by the inverter is very complicated.Therefore,the mathematical model of permanent magnet synchronous motor based on the distorted voltage,current and back EMF is established,which provides theoretical support for the further research of current harmonic suppression algorithm.Secondly,the control algorithm of low order harmonic current suppression based on multi-rotation proportional integral controller is studied in this thesis.The strategy is to introduce harmonic current signal feedback link through harmonic injection compensation signal method,and then suppress the main harmonic current component of the motor.First,the harmonic components of the current in the synchronous rotating coordinate system are extracted,and then the harmonic components are obtained by the harmonic steady state voltage equation with the harmonic component being zero as the control objective.Then the harmonic voltage compensation component is positively fed back to the space vector pulse width modulation(SVPWM)reference input terminal,and the harmonic voltage in the motor current can be suppressed by controlling the output of the inverter circuit.Since SVPWM actually controls the voltage,the back EMF also has harmonic components,so only controlling the motor voltage cannot directly control the harmonic current.Therefore,the hysteresis AC regulator is used to suppress the current harmonics of specific times.This is because the hysteresis AC regulator can adjust the AC signal without static error.The current harmonic semaphore extracted in the DQ coordinate system is directly compensated at the given end of the intersecting direct axis current in order to suppress the motor current harmonic.Finally,the PMSM vector control speed regulation system based on the multi-rotation proportional integral controller and the hysteresis AC regulator harmonic injection compensation signal is built on the MATLAB/Simulink simulation platform.The simulation results of the two algorithms for suppressing harmonics are compared,and it is shown that both can be Suppress the harmonic components of the motor current,but the latter has a more obvious suppression effect. |
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