Influence of Selective Harmonic Elimination Technique of Multi-Level DC/DC Converter on Second-Life Battery Performances

This paper is part of a research project, which aims to investigate the possibilities of using the second life batteries after their replacement from the plug-in electric vehicles (PHEVs), hybrid electric vehicles (HEVs) and battery electric vehicles (EVs) for smart grid applications. In these applications, the power electronics converters (PECs) play a key role in the development of a high performance integrated system. This paper shows that the performance of the batteries will be affected by the performance of the PECs, which are utilized to achieve the integration of the batteries with the smart grid. Therefore, this paper demonstrates the impact of the Multi-Level DC/DC Converter (MLDC) on the performances of the battery system. The Selected Harmonic Elimination (SHE) technique is used to realize the control system of the Multi-Level DC/DC Converter (MLDC). In addition, the battery model of a Lithium-ion iron phosphate (LFP) with different capacities (7Ah, 14Ah and 20Ah) is used to investigate the impact of the switching angles and the voltage levels of each module on the performance of each battery module. This system (including the battery modules, MLDC and electric load) is designed and verified by using MATLAB/Simulink environment. Furthermore, this paper provide an extended analysis to select the proper switching angles for different units of MLDC, which can be used for both of designing the control strategy of second life battery and achieving less Total Harmonic Distortion (THD) at AC side.