EMI Suppression Method For Servo System

The servo system is widely used in various fields of social life with its superior performance.The servo driver generally uses pulse width modulation technology.However,due to the existence of the switching tube in the driver,the switching process will cause serious electromagnetic interference in the servo system.The voltage control method can reduce the overshoot and oscillation of the switch tube off voltage,and reduce the electromagnetic interference of the system;the DC side bus capacitor of the inverter generally uses an electrolytic capacitor.When the ambient temperature is high,the electrolyte in the capacitor will volatilize,causing electricity The reduced capacity seriously affects the reliability of the system.Therefore,the electrolytic capacitor on the DC bus can be replaced with a thin film capacitor with a longer life and a smaller capacity,thereby forming a small bus support capacitor drive system.When the inverter DC side of the servo drive After the support capacitor uses a small support capacitor,the bus voltage cannot be stabilized,resulting in the inverter output voltage periodically entering the low value area.After the SVPWM overmodulation algorithm is used,the voltage fluctuation in the low value area can be compensated back.This thesis mainly studies the EMI suppression method of the servo system,the main contents are as follows:(1)First introduce the research background and significance of the subject,analyze the research status of the electromagnetic interference suppression method of the servo system,the research status of SVPWM overmodulation and the research status of small bus support capacitor motor drive,and turn off the switch tube voltage overshoot And the voltage fluctuations caused by the inverter under the support capacitance of the small bus are the research focus.(2)Then the basic theoretical analysis was carried out,the principle of SVPWM overmodulation,the relationship between bus voltage fluctuation and supporting capacitance,and the modeling and analysis of the switching process of the switch tube were introduced,and the mathematical expression of turn-off voltage overshoot was obtained.(3)According to the mathematical expression of the switch-off voltage overshoot,the influence of different factors on it is analyzed.For the switch-off process of the switch,the influence of different parasitic parameters on the switch-off process of the switch is analyzed.Changing the driving voltage can reduce the overshoot and oscillation of the switch-off voltage.For this purpose,a gate voltage control circuit was designed.During the turn-off process,the driving voltage can be changed in time through the control circuit,and simulations were carried out to verify the theoretical correctness.(4)Then,with the small bus support capacitor for the inverter,the bus voltage cannot be stabilized,and the inverter output voltage will fluctuate.The SVPWM overmodulation algorithm can compensate for the voltage fluctuations,and different overmodulation areas can reduce the voltage.The range of fluctuation compensation is different.Simulation analysis is carried out to verify the correctness of the theory.(5)Finally,when the reference voltage vector is less than the radius of the inscribed circle of the regular hexagon and the bus voltage fluctuates,the SVPWM overmodulation algorithm can be used to simulate the voltage fluctuation compensation.Then based on MATLAB/Simulink,under the bus voltage fluctuation,the use of The double closed-loop control method of permanent magnet synchronous motor with SVPWM overmodulation algorithm was modeled and simulated.The analysis of the introduction of overmodulation algorithm to the motor speed,d 、 q-axis current waveform,three-phase current waveform,line voltage waveform and line voltage harmonics The effect of content.