Current and voltage control system designs with EKF-based state-of-charge estimator for the purpose of LiFePO4 battery cell charging

Adaptive Constant-Current/Constant-Voltage Charging of a Battery Cell Based on Cell Open-Circuit Voltage Estimation

“…The main contributions of the paper are: (i) a systematic design of the equivalent circuit model parameter estimator using the SRAM technique and Lyapunov stability criterion for proof of estimated parameter convergence, (ii) establishing an indirect battery SoC feedback based on a priori known OCV(SoC) characteristic, and (iii) expanding the overall CCCV control strategy with an additional degree of freedom when controlling the battery SoC during charging. The effectiveness of the proposed augmented charging control system is verified by means of simulations using a realistic model of the LiFePO 4 cell presented in [50].…”

“…Due to the nonlinear character of the internal battery model, the so-called extended Kalman filter [48] or unscented Kalman filter [49] are typically used for that purpose. Reference [50] recently demonstrated that using an SoC estimator has good potential for charging speed improvement when compared to the conventional CCCV charging strategy, wherein the adaptation to temperature-related battery model parameter variations can also be employed [40]. These approaches, however, still require a rather complex battery model typically comprising multi-dimensional parameter maps (in the form of look-up tables), which may also require online updating [51].…”

“…Figure 1 shows the dependences of averaged model parameters of a commercial 100 Ah LiFePO 4 battery cell (see [20]) with respect to state-of-charge ξ for the case of battery charging, which were originally recorded in [52] and further elaborated upon for the purpose of a battery charging study conducted in [50]. Averaged profiles of battery polarization and equivalent series resistance R p (ξ) and R b (ξ) are shown in Figure 1a,b, whereas Figure 1c shows the OCV vs. SoC characteristic (U oc (ξ) curve).…”

“…Figure 3a shows the conventional control system structure used for CCCV battery charging based on the inner current control loop with a battery terminal voltage-limiting outer feedback loop, denoted herein as the CCCV-VL control strategy [50]. This type of charging strategy represents a state-of-the-art approach to CCCV charging according to [22], and is used herein as a benchmark case.…”

Introductory remarks on the special issue of Optimization and Engineering dedicated to SDEWES 2021 conference

“…Electrical battery technologies in transportation and stationary applications have become increasingly important to the functioning of electricity supply systems. Pavković et al (2022) present two control systems concepts for constant-current/ constant-voltage battery charging. These rely on a cascade-type system arrangement with the overlaid proportional-integral (PI) controller having command on the battery-charging current reference to the inner control loop for current control.…”