Route Optimization Equalization Scheme Based on Graph Theory for Liquid Metal Battery Strings

Abstract

In order to solve the inconsistency problem of series connected liquid metal battery (LMB) strings, a route optimization equalization scheme is proposed in this article. In terms of balancing topology, a modular double-layer cell-to-cell balancing topology based on inductor and flyback multi-winding transformer is designed, which can transfer energy between any two batteries within or among modules. For control strategy, an equalization strategy based on graph theory and ant colony optimization (ACO) is proposed, which has been compared with the traditional maximum/minimum equalization control strategy. The static condition simulation results show that compared with traditional equalization strategy, the balancing speed of the route optimization control strategy is improved by 88.62%, and the balancing efficiency is increased by 19.43%. Moreover, the inconsistency problem of the battery strings can be significantly improved under both static and dynamic conditions. Therefore, by improving the balancing effect, the proposed scheme can not only effectively avoid overcharging or discharging problems, but also increase the consistency, available capacity and service life of liquid metal battery strings.