| Title |
A Study on the Cause of CMV and Leakage Current, and Mitigation Strategy on the Lithium-ion Battery of ESS |
| Authors |
김승호(Seung-Ho Kim) ; 최형석(Hyoung-Seok Choi) ; 김진용(Jin-Yong Kim) ; 한 아(Ah Han) |
| DOI |
https://doi.org/10.5370/KIEE.2021.70.1.061 |
| Keywords |
ESS; Lithium Ion Battery; Stray Capacitance; CMV; Delta-V; Leakage Current; Conduction Noise; Isolation Transformer |
| Abstract |
ESS(Energy Storage Systems) using lithium ion battery are rapidly increasing their capacity because they can efficiently store electrical energy in a small area with high energy density. However, 29 fire accidents have been reported in Korea for last 4 years.
Up to now, the root cause of ESS fire has not been clearly defined, but some lithium ion battery manufacturer assert that the reason of fire may be caused by CMV(Common Mode Voltage) and leakage current. This study investigated the mechanism, measuring, acceptable level, and mitigation of CMV and leakage current through experimental field analysis with its corresponding simulation. The stray capacitance of IGBT module and lithium-ion battery are investigated as the cause of CMV and leakage current, and the magnitude variation of CMV and leakage current by the type of system earthing of the AC side is investigated too, then this paper suggested the use of an isolation transformer as a mitigation method. In addition, it was analyzed how the use of an isolation transformer can reduce CMV and this study proved that the installation of an isolation transformer is a complete and fundamental solution to reduce both CMV and leakage current by simulation and field measurement results. On the other hand, this study found the shape and period of the waveform of CMV and leakage current are completely identical, and prove that these two are produced by the same cause and the leakage current was also demonstrated to be lowered when the CMV was lowered. On the other hand, based on the analyzing the path of the leakage current flow in the grounded system and the non-ground systems, this study found that it was reasonable to measure CMV and leakage current on the DC side of PCS, and this was proved by P-Sim simulation and field experiments. |