Analysis of Lithium-Ion Battery CMV Characteristics According to Grid-Connected ESS Operation

In the DC link of a lithium-ion battery system, common mode voltage(CMV) is generated due to grounding. CMV is mainly generated by grounding imbalance, ground potential difference, and signal interference within the system, and affects the performance of the battery system. In particular, CMV can cause electromagnetic interference(EMI) in the high-frequency range or reduce efficiency during the power conversion process, which can adversely affect the reliability of the power system. Therefore, in this paper, we analyzed the characteristics of CMV generated due to grounding of a lithium-ion battery through hardware experiments under various conditions. To this end, we compared and analyzed the CMV characteristics generated during charging and discharging according to the ESS operation during the day and night. In addition, we analyzed the variation of CMV according to the presence or absence of load when charging the battery through photovoltaics(PV) and when connected to the grid.