No abstract

Redox flow batteries are one of the most promising technologies for large-scale energy storage, especially in applications based on renewable energies. In this context, considerable efforts have been made in the last few years to overcome the limitations and optimise the performance of this technology, aiming to make it commercially competitive. From the monitoring point of view, one of the biggest challenges is the estimation of the system internal states, such as the state of charge and the state of health, given the complexity of obtaining such information directly from experimental measures. Therefore, many proposals have been recently developed to get rid of such inconvenient measurements and, instead, utilise an algorithm that makes use of a mathematical model in order to rely only on easily measurable variables such as the system’s voltage and current. This review provides a comprehensive study of the different types of dynamic models available in the literature, together with an analysis of the existing model-based estimation strategies. Finally, a discussion about the remaining challenges and possible future research lines on this field is presented.

This work presents the preliminary findings of a feasibility study for a class of sliding mode differentiators to be used in an on-line parameter estimation methodology for vanadium redox flow batteries (VRFB). Specifically, three high-order continuous differentiators are considered: a Standard Differentiator; a Filtering Differentiator, which excels the former by incorporating rejection to large noises small in average; and a Tracking Filtering Differentiator, which produces smooth consistent derivatives while inheriting the noise rejection capabilities from the previous one.To model the vanadium redox flow batteries an equivalent circuit model is employed, whose time-varying parameters are estimated by a recursive least squares algorithm with forgetting factor, that requires the VRFB measured voltage and current, together with their derivatives. To assess the performance of the different differentiation algorithms in obtaining reliable values of the VRFB parameters, the storage system is excited with standardised current demand profiles. Finally, representative simulation results are presented and discussed.

No abstract