Study of Electromagnetic Interference in Lithium-ion Power Battery Pack 2019-01-1060
When electric vehicle speeds up or slows down, rapidly changing current and voltage (di/dt and du/dt) would occurs in its lithium-ion power battery. In this way, the impedance of power battery would changes with parasitic parameters because that the ion transport in electrolytes would influence diffusion effect and polarization effect of battery. Thus, the lithium-ion battery cannot be regarded as ideal component in high frequency, which could cause unpredictable problem in electromagnetic interference (EMI). However, most previous studies took lithium-ion power batteries as disturbed objects or transmission routes, which ignore the electromagnetic interference of battery itself. Based on it, this paper analyses the internal mechanism of EMI in lithium-ion power battery, and simulates the distribution of electromagnetic field as well as it corresponding interference suppression measures.
Firstly, the second-order low-frequency equivalent circuit of lithium-ion power battery is established. Besides, the test platform for parameter extraction of battery monomer is built. The parasitic parameters are extracted through numerical calculation after testing. The high-frequency equivalent circuit of power battery is consequently established.
Secondly, peripheral circuit of lithium-ion battery including DC/AC and DC/DC systems is built by joint simulation of saber and Simulink to study EMI of sensitive components in battery system such as sensors. The current at DC bus is obtained to import to CST as excitation source to conduct co-simulation of field and circuit for distribution of electromagnetic field in battery.
Thirdly, the lithium-ion battery pack is optimally designed in EMI. The structure and parameters of the filter are selected according to energy distribution frequency band of EMI signal. Results of simulation and testing turn out that the designed filter could decrease EMI effectively.