Research On Electromagnetic Interference Filter Of Three-phase Motor Drive System

Electromagnetic interference(Electromagnetic Interference,EMI)is a widespread problem in power electronic systems.The power converter is widely used in power electronic devices are currently using pulse width modulation(Pulse Width Modulation PWM)technology to transform the power and control,the performance index of motor system can be greatly improved.However,the semiconductor devices in the power converter produce a large number of harmonics of the discontinuous voltage and current,conduction and radiation noise,resulting in the EMI problem.The new power semiconductor devices can increase the switching speed,which helps to reduce the size of the converter and reduce switching losses,but further exacerbated the problem of EMI.The production of EMI makes it possible to use EMI filters in the design of most converters.For example,the motor of the aircraft must be EMI filter.EMI filters are usually the main elements that determine system volume,weight and cost.The traditional method of designing EMI filter is to create a complete system prototype,and then measure the attenuation of the EMI signal.This method of measuring EMI is not the best solution,this approach often leads to more time consuming and more expensive.In order to solve this problem,and at the same time to create a general EMI filter design method,first of all,the motor drive system modeling.The linear behavior of different components of a typical motor drive system is modeled,such as semiconductor devices,passive components,interconnect cables and motors.This behavior model can be applied to both the motor drive circuit and the filter design,thus providing a means to evaluate the performance of the EMI and to design the EMI filter without the need for system prototype measurements.In this paper,we use the new method to reduce the EMI problem of the motor drive system.Impedance balance method is in common mode(Common Mode CM)voltage source around insert passive components to establish a balanced Wheatstone bridge,through the return current offset a bridge for another bridge input or output current of CM,EMI will be reduced.The passive component is loaded only with the CM current,so it can be much smaller than the traditional CM filter assembly that must carry full input or output current.