Abstract: In order to meet increasing safety demands from coal industry and mining company, a lead acid and lithium iron phosphate (LFP) based battery energy storage is developed for a megawatt level emergency power supply in Pinggou coal mine of Wuhai, Inner Mongolia. If the local power grid works normally, the proposed system compensate the reactive power instead of the use of traditional static capacitor. When there is a local grid failure, the energy storage system provides stable power to extremely critical loads of coal mine for at least 30 min. Besides, the proposed energy storage system could also play a role in the ‘peak shaving’ and smoothing distributed energy generation for the demand side. To ensure safety, reliability and sufficient lifetime, the work is focused on the selection of batteries, capacity ratio of different batteries, circuit topology and smart control strategy design of the power conversion system.

Key words: energy storage system, power conversion system, battery, coal mine grid