Modeling And Suppression Of Electromagnetic Interference In Servo Drive System

Servo drive systems are now widely utilized in industry and transportation,including new energy vehicles,industrial robots,spacecraft,rail transit and other high-tech fields,due to the efficient operating characteristics.However,there exist a large number of high-frequency switching devices inside the servo driver,which causes serious internal electromagnetic interference(EMI)in the system.Besides,the driver’s being compact makes the electromagnetic environment of the driver more complicated.There are two power supply systems within the servo drive system,i.e.,high-voltage power supply and low-voltage auxiliary power supply.The high-voltage power supplies the motor through the inverter bridge in the driver,and the low-voltage power supplies to the drive circuit,control circuit,and other sensitive equipment through the switching power supply in the driver.The interference on the high-voltage side is more serious than that of the low-voltage side,and the interference of the high-voltage side can be conductively coupled to the low-voltage auxiliary power bus.Therefore,it is of great significance to study the EMI coupling mechanism between the high-voltage bus and the low-voltage bus,and to establish its high-frequency model effectively.Firstly,in this paper,a general servo system is used as the research object.Aiming at the problem of EMI coupling between the high-voltage side and the low-voltage one,a careful research is conducted.EMI receiver and oscilloscope are used for EMI testing,and a test method for separating differential mode(DM)current and common mode(CM)current was used.The interference sources of servo drive system,the main path of interference propagation and the domain components of interference was determined in the experiments.And the EMI receiver test results and oscilloscope test results were compared,as well.Secondly,based on the experimental results of a large quantity of tests,simulation models were built in both Matlab and Saber simulation platform.A high frequency model and a CM equivalent model of the servo drive system are established in Matlab.A method of fitting impedance spectrum with Monte Carlo algorithm to extract CM impedance parameters was adopted,the test results and simulation results are compared to verify the accuracy of the model.Finally,according to the simulation model,the key circuit of the interference coupling in the servo drive system can be restrained in a targeted manner.This paper adopted a comprehensive suppression method through transformer optimization and filter design.The transformers in the auxiliary switching power supply within the interference propagation loop is optimized,and the design of the filter was carried out based on the optimized test results.In this way,the EMI on auxiliary power lines was reduced significantly with a lower cost.