Single Flow Nickel Zinc Battery Pngv Equivalent Circuit Modeling And Performance Analysis

Redox flow batteries due to their merits in large-scale energy storage, fast charging and discharging conversion rate and long cycle life,have attracted more and more attention. In the year of2007,Research Institute of Beijing chemical defense developed single flow nickel-zinc battery by analyzing the characteristics of single flow lead-acid batteries and traditional nickel-zinc batteries.This battery solves the problem of zinc dendrite in the traditional nickel-zinc battery and the cycle life is improved.Since it can be refreshed to maintain its performance and need not membrane,making it has the high research value.In order to better study the single flow nickel-zinc battery, it is essential to model the battery and analyze its voltage feature.Firstly,the voltage relationship of the single flow nickel-zinc battery is analyzed.The inner ohm resistance of the battery is equivalent to a resistance.The change of the polarization voltage is similar to the RC network response curve,so a RC network is used to represent the polarization voltage,the open circuit of the battery is equivalent to a power source,the change of open circuit voltage in the charging/discharging process is equivalent to a capacitor,then a PNGV model is established.The change of the terminal voltage during the charging/discharging process versus the charging/discharging time is derived,after that,The Hybrid Pulse Power Characterization(HPPC) text is recommended to extract the model parameters.Finally,the model is validated by using the experimental data.Based on PNGV model and electrochemistry mechanism of the single flow nickel-zinc battery,the electrochemical polarization produced by the electric double layer and concentration polarization produced by the diffusion are equivalent to two RC networks respectively.An improved PNGV model of the single flow nickel-zinc battery is proposed in this paper,then a zero-order holder is adopted to discretize the model to obtain the discretization model related to time.The least square method based on forgetting factor is used to extract the model parameters online and predict the change curve of the battery voltage.At last,The improve PNGV model is compared with the original PNGV model to evaluate the advantages of the improved model.The battery has been tested under various condition,the results are obtained as following:1)When the discharge current is less than120A,the capacity efficiency is greater than95%;The larger discharge current it is, the shorter discharge time it is,but the capacity efficiency becomes lower.2)Compared with the continuous discharging,the intermittent discharging and discharging with small current after discharging to the cut-off voltage are all can raise the capacity efficiency.3)The capacity efficiency is higher than95%under different depth of charging/discharging,so we can choose the depth of charge according to actual demand.4)The battery performance is lower than85%at about200cycles,it needs to refresh to recovery its capability.