Analysis And Suppression Of Conducted Electromagnetic Interference In Z-source Inverter Systems Of Hybrid Electric Vehicles

In recent years, industrial pollution and energy problem have become increasingly serious. Thus, the resulting environmental problems have gained the focus of public attention. Hybrid electric vehicle is a new energy vehicle, which not only can save energy and reduce pollution, but also has a broad application prospect. However, compared to conventional vehicle, the power electronics devices used in the hybrid electric vehicle have been greatly increased, leading to serious electromagnetic compatibility problem to the automobile system. In addition, inverter system of the hybrid electric vehicle is one of the main sources of electromagnetic interference. The EMI(Electromagnetic Interference) produced by the inverter system can seriously affect the normal working of automotive electronics, resulting in adverse impact on safe driving of the vehicle and external electromagnetic environment. The main object of this dissertation is the Z-source inverter system in the hybrid electric vehicle, and its conducted EMI problems are also studied. The main content includes:Firstly, the structure and working principle of Z-source network are introduced and the oretical values of the capacitors and inductors in the Z-source network are calculated. Combined with working principle of the inverter system in the hybrid electric vehicle, working process of the inverter system under open state, through state, and non-through state and main noise source and its propagation path of the conducted EMI are analyzed. Then, the equivalent circuit model of each component in high frequency is established, including motor drive, LISN(Line Impedance Stabilization Network), and cable. The parasitic capacitance generated by the components of the inverter system at high frequency is analyzed, and parameters of it have a big impact on the conducted EMI. The influence of various parameters on the conducted EMI is also predicted. Furthermore, the common mode and differential mode interference simulation circuit are constructed in MATLAB. The interference generated in the circuit is simulated and analyzed, and relevant parameters are adjusted to observe the influence of different parameters on the interference.Secondly, suppression method of the conducted EMI in Z-source inverter system of the hybrid electric vehicle is investigated. By analyzing the conducted EMI of the inverter system theoretically, the interference source need to be suppressed can be determined, and then targeted inhibition and improvement measures can be implemented. Moreover, an active compensation circuit is used to suppress the conducted EMI generated by the inverter system in this dissertation. It can compensate the common mode current generated by the inverter system, leading to reduced common mode interference. The structure, working principle, and design method of the compensation circuit is discussed at length.Finally, the active compensation circuit and Z-source inverter main circuit are connected, modeled, and simulated in MATLAB. Then, the obtained simulation results are compared with the results without an active compensation circuit. The main conclusions are as follows: the compensation circuit can reduce the EMI generated by the Z-source inverter system in the hybrid electric vehicle effectively, the interference is suppressed, electromagnetic environment of the automobile is improved, and the effectiveness of the proposed method is validated.