The study of dynamic response model and energy optimization management process for the application of vanadium redox flow battery in microgrid

In order to realize the reasonable configuration and efficient operation of vanadium redox flow battery (VRB) in microgrid containing renewable energy and the traditional power system such as supercritical carbon dioxide coal-fired power generation system, an advanced dynamic response model of VRB is constructed and a feasible energy optimization process is proposed in this paper. First, the U_battery-I_battery-SOC curves are obtained based on the improved electrochemical mode. Key parameters for the simplified equivalent circuit model of VRB are further analyzed to refine the dynamic response model of VRB with fast computational capabilities. Second, the optimized configuration design method of microgrid is proposed with the consideration of investment costs, operation costs, economic benefits and rates of renewable energy utilization. Finally, the energy optimization management process for microgrid is proposed combining with the load distribution algorithm aiming at efficiency. The results are presented as follow. First, the combination of the fitted curve and the experimental data can be used to calculate the key parameters of the simplified equivalent circuit model of VRB. In the state of charge, the maximum U_battery of VRB of 86.14 V is obtained at the I_battery of 10A and SOC of 0.99. Second, with the lowest average daily cost as the optimization target, the optimal rated power and rated capacity of VRB are 891 kW and 7344 kWh, respectively. Finally, the change frequency of load distribution results for grid, VRB and S-CO₂ in microgrid matches their dynamic response characteristics. The VRB energy storage system is operating at an efficient level with a time average efficiency of 82.50%. The time average efficiency of S-CO₂ generation system is up to 43.53%. The study can provide a theoretical reference for the optimal operation of the VRB energy storage system.