| In order to solve the problem of oil supply and environmental pollution, developing the new energy automobile has become the national strategy. Electric vehicle(EV), as an important part of new energy automobile, gets consider development in recent years. Compared to the traditional vehicle, the working power electronic devices in EV generate serious EMI which lead to serious problems.This study aims to research the EMC problems for motor drive system of EV and the generating mechanism、propagation path and prediction methods are discussed in this paper. The research thinking and approaches which is used to solve EMC troubles in motor drive system can be generalized to other vehicle electronics. The main research contents and results are listed as follows.1) Through analyzing the mechanism of EMI in motor drive system, the main interference sources is produced by the fast rise(fall) time of the switching transient in the converter. In this part, the influence factors of voltage spectrum, such as frequency, amplitude, duty ratio, rising(falling) time and so on, are discussed to lay the foundations for establishing the EMI prediction model.2) A method based on vector fitting(VF) is proposed to model a star or delta connection topology motor with high accuracy in a wide frequency range. The proposed method is verified by experimental measurement and simulation, it also can be used to model other AC motors, and therefore, this method has certain common ability.3) A prediction model of conducted interference for motor drive system in no load conditions is established in this part. The high-frequency models of various parts of the system are proposed, including motor model based on VF method, cable model based on theory of transmission lines, and parasitic capacitance model based on ”second measurement” an so on. A system model is composed by all these sub-models and it has been verified via practical test. Moreover, parametric analysis is carried out to the common model simulation circuit, and the influence on common mode current by the parameters such as parasitic capacitance, cable length and the motor winding capacitance is discussed at the same time.4) The experimental platform which can meet the various working conditions of pure EV motor drive system is established, and then, the conducted EMI of each working conditions is measured and contrast with each other. The conducted EMI predictive model of motor drive system is established in no-load, 45N·m and reverse charge working condition, respectively. The modeling method is universal and transplantable by contrast the simulation and measurement results of the interference voltage and current.5) Analyzing the radiated emission mechanism of conductor, confirming the research spectrum of the single motor drive system through experimental method, the radiated emission predictive model is established with common current measured on the three-phase cable as the interference source. By jointing simulation technology, the complex CATIA model of EV is simplified to the finite element simulation model. The radiated EMI simulated model of the EV is established on the basis of single model and the comparison between experiment and calculation result of the electric field certify the validity of the car body FEM model, meanwhile, it indicated that the EV radiated simulating model can be used to predict the radiated EMI. |
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