Modeling And Performance Analysis Of Zinc Nickel Single Flow Battery Energy Storage System

With the rapid development of renewable clean energy,which contains solar energy,wind energy,a corresponding large-scale energy storage device is in an urgent need to eliminate fluctuation and intermittent energy storage.Flow battery has received much concern for its performance-power and capacity can be independently designed,be suitable for all kinds of storage places,low life-cycle cost,this merits has potential application in large emergency power supply system,and smart grid.The zinc–nickel single flow battery(ZNB)proposed in recent years is a cost-effective flow battery,which uses a single electrolyte and no ion exchange membrane,and exhibits the advantages of a simple structure,extended life cycle,high reliability and nonpollutionThis paper builds a simulation model for the single ZNBs energy storage system,series-parallel battery pack equivalent circuit models are simulated with several stacks and explores the influence of the inconsistency of single cell on the performance of battery pack.Providing a reliable foundation for the research and application of large-scale energy storage systems for ZNBs.The work of this paper can be expressed as follows:(1)Based on 2kW ZNBs modular system with pipeline design scheme of single side and bilateral.This paper builds a simulation model for the single ZNBs energy storage system.Flowmaster is used to simulate and compare different pump,main pipe diameter,branch pipe diameter and control valve matching scheme.In order to improve the efficiency of pump and the practicality of energy storage system with flow rate and velocity.The results of simulation and experiment provide a reference for further research and engineering applications.(2)Investigating a battery system with ZNB stack by a series-parallel-connected system based on two-order Thévenin equivalent circuit model for single-cell stack and the parameter identification of the experimental model.Two single-cell stacks are simulated with three kinds of series-parallel battery pack equivalent circuit models,and compared with the experimental data.Results show that the simplified equivalent circuit model can accurately characterize the voltage of discharge for the series-parallel battery pack.The relative errors of the series/parallel battery pack are 0.8% and 0.71%.Furthermore,the simulation and experimental test data of the large-scale series-parallel system are compared,thereby indicating that the simplified equivalent circuit model of the series/parallel battery based on the two-order Thévenin model can provide a high-precision prediction for the external characteristics of a large-scale ZNB energy storage system.(3)With the experiment of investigated the effects of the charge/discharge current,initial SOC,internal resistance,and initial nominal capacity on the performance characteristics and efficiency of series-parallel battery to address the inconsistency problems of ZNB during the use of series-parallel battery pack.Experimental results show that the differences in charge/discharge current,initial SOC,and initial capacity change the inconsistency of battery pack.The difference in initial nominal capacity is the most influential factor,whereas the charge/discharge current is the least influential factor.Meanwhile,the inconsistency of internal resistance increases,which enlarges the energy loss of the battery pack and increases the temperature.The optimum operating current is below 30 A and the optimum deviation in initial SOC is within 10%,at which the inconsistency of the battery group is satisfactory.