Analysis and Evaluation of a Fault-Tolerant Strategy for Module Vanadium Redox-Flow Batteries

A battery energy storage system (BESS) can provide flexible energy management solutions for power systems. A BESS with the ability to maintain functionality can greatly affect power system reliability. In this paper, two fault-tolerant (FT) strategies (i.e., a lower-rated power mode and times-rated power mode) and four reliability evaluation indexes are proposed for vanadium redox-flow batteries (VRFBs) in power systems. Each strategy is evaluated in terms of both power and energy response capabilities of VRFBs and verified via experiments. The testing results show that the lower-rated power mode is suitable for energy applications, such as load shifting, and the times-rated power mode is suitable for power applications, such as power smoothing. The reliability evaluation index, considering power and energy, is an extension of the traditional index and can be used to quantitatively evaluate the FT method in the energy storage field.