Low-Complexity Fast Charging Strategies Based on Explicit Reference Governors for Li-Ion Battery Cells

Abstract

This paper proposes and compares a new family of low-complexity control schemes for the fast charge of Liion battery cells accounting for degradation constraints. These schemes are based on a two-levels architectures, where a lowlevel linear quadratic regulator (LQR) ensures stability and fast tracking of the applied reference, while an outer control layer, based on an explicit reference governor (ERG), enforces constraints satisfaction by manipulating the applied reference of the lower level. The ERG is based on the construction of a suitable Lyapunov level set contained inside of linear constraints. The main challenge to build a performing ERG for the fast charge of Li-ion batteries is how to choose a convenient Lyapunov function for non-convex constraints arising from the electrochemical model of the battery. This paper proposes and compares four different approaches to obtain performing Lyapunov functions for a concave constraint evaluating the impact on the charging time of a Li-ion battery and on the required computational time. Experimental validations on commercial LCO battery cells (Turnigy nano-tech 160 mAh) show a trade-off between the four methods computational time and the charging time.Index Terms-reference governors, explicit reference governor, state feedback control, lithium-ion batteries, fast charging, computationally-efficient constrained control, nonlinear concave constraints I. INTRODUCTIONS ince the release of the first lithium-ion (Li-ion) battery cell back in the 1990s [1], research on this technology has mainly focused on developing new battery materials to improve power delivery and extend lifespan. So far, little attention has been paid to improve the current battery charging protocols in order to reduce the charging time while increasing lifetime expectancy and safety. As the number of batterypowered devices increases in the daily life, customers are not willing to wait several hours for fully charging their batteries, Manuscript received August 18, 2019. 2nd Version Resubmitted April, 2020. This work is performed within the framework of the BATWAL project (Convention 1318146, PE PlanMarshall 2.vert) financed by the Walloon region.

An Optimized Fuzzy Controlled Charging System for Lithium-Ion Batteries Using a Genetic Algorithm

“…It is well known that fast charging is a preferred way of charging batteries, but it causes an increase in battery temperature that results in an undesired degradation of its performance and in an accelerated ageing. The authors of [6] propose low complexity fast charging strategies for Li-ion battery cells that take into account explicit reference governors.…”

Cycle life and influencing factors of cathode materials for lithium-ion batteries--a case study of lithium-cobalt oxides

“…Still, due to the lack of Co resources and its high price, people are constantly looking for better substitutes, such as LiNiO2, LiMn2O4, and other new materials. Still, the actual battery performance of these materials is not as good as that of LiCoO2 [16][17]. In order to obtain LiCoO2 with higher discharge voltage and better cycle stability, LiCoO2 has been doped with different elements such as Al, Mg, F, Ni, etc.…”