Optimal Control Strategy of Echelon Battery Energy Storage System Based on Battery Health State

The life cycle of the battery can be extended and the waste of resources can be reduced by using the retired battery in echelon. In order to avoid the deep charge and discharge of the battery with lower health state, and make full use of the potential of the battery in good condition, a targeted control strategy is proposed, which takes into account the health state of the echelon battery as a key factor. Under the background that the echelon energy storage aims at coordinating the output plan of new energy power stations, firstly, each energy storage unit of the retired battery energy storage system is grouped based on the difference of the health state of the retired battery, and the power distribution of different energy storage units is carried out according to the energy storage charge and discharge demand, and a differentiated control strategy is proposed. Then, based on the rain-flow counting method and the equivalent cycle life method, the life of the cascade energy storage is evaluated. Finally, the results of an example show that the proposed control strategy has significant advantages over the existing control strategies in prolonging the working life of the echelon battery energy storage system.

I. Introduction

At present, driven by national policies and market choices, China's new energy vehicle sales have grown rapidly. The indispensable power battery for new energy vehicles is also booming. According to industry estimates, the power battery capacity required by China's new energy vehicle market will be about 1000 to 1200GWh by 2025 [1], but the on-board power battery capacity is no longer suitable for electric vehicles if it is less than 80% [2]. The total number of retired power batteries in China has reached 25GWh in 2020 and is expected to exceed 100GWh in 2025 [3]. If a large number of retired power batteries are directly scrapped, it will not only lead to waste of resources but also cause environmental pollution and safety problems. The application of retired power batteries in echelon energy storage system can maximize the value of retired batteries, and has a significant role in promoting the development goals of environmental protection and resource conservation.