Peak Power Estimation Method of Vanadium Redox Flow Battery for Solar-Battery Powered Electric Vehicle Charging Stations

Abstract

Vanadium redox flow batteries (VRBs) are promising energy storage systems suitable for large-scale solar-battery integrated electric vehicle charging stations. Such a system can mitigate the impact on the grid system due to high and random charging power demand. In this application, an accurate estimation of the peak power of VRBs is the premise of its safe and efficient operation. This work thus proposes a peak power estimation method based on economic model predictive control (EMPC) is thus proposed. This method first establishes an integrated equivalent circuit model consisting of an electrical and a hydraulic submodel. With the model, the state of the VRB and terminal voltage can be accurately predicted under given input excitation. Then, the receding optimization method is carried out based on the VRB model and estimated state. Finally, the proposed EMPC-based peak power estimation scheme is numerically verified via computer simulation. The results show that by optimizing the current and flow rate of the VRB, a safe operating area for charging electric vehicles can be obtained for practical use.