| With the wide application of lithium-ion batteries in the national economy,the disadvantage that the energy and power characteristics of lithium-ion batteries can not be considered at the same time is particularly prominent.In actual design,it is often necessary to make a trade-off between energy and power.In addition,in the context of large-scale use of batteries,batteries need to be connected in series and parallel to meet the demand for voltage and capacity.Due to the inconsistency of capacity,internal resistance,polarization,initial SOC,etc.between the cells,most battery cells of energy storage battery packs can not be fully charged and discharged,and the cycle life of the battery will also be affected.In this paper,energy-type battery and power-type battery are taken as research objects,and two different types of battery parallel simulation considering cycle life and the optimal management strategy for energy storage system applications are studied.The specific research content and work are as follows:(1)Battery capacity,OCV-SOC curve and other experiments were carried out by battery testing equipment and its data acquisition system,and battery model parameters were identified.The MATLAB/Simulink platform was used to build a single cell equivalent circuit simulation model.The accuracy of the simulation model was verified by the constant current charging experiment and the dynamic stress test working condition experiment.The absolute value of the error was within 1%.Considering the inconsistency between the cells,the MATLAB simulation model of passive hybrid parallel connection of energy-type battery and power-type battery was established.The initial SOC calculation method for different types of parallel battery packs was proposed.The simulation model of the parallel connection of power battery packs with energy battery packs through DC/DC converter was carried out.Moreover,the simulation results of different parallel connection modes of power-type battery and energy-type battery were analyzed.The simulation results showed that the high power characteristics of LTO in passive hybrid battery energy storage system can not be effectively utilized,and the power distribution was coupled with battery parameters.While the power distribution of active hybrid battery energy storage system was controllable,and the SOC of battery can be restrained.(2)Taking NCM/graphite batteries as the research object,the experiments of battery cycle life under different interval and rate were designed,and related experiments were carried out by using battery test equipment.Two kinds of lithium-ion battery operation methods were compared and analyzed from two aspects of battery capacity and cumulative energy.The results showed that the cycle life of batteries can be increased by more than 6.5%and the cumulative discharge energy of hybrid battery energy storage system can be increased by more than 5.6%by optimizing the method of use.The variation characteristics of the capacity increment curve were used to analyze the degradation characteristics of the battery cycle life during the aging process.Thermodynamic losses of batteries in 10%?85%SOC use interval were mainly caused by lithium ion loss,while those in 15%?80%SOC use interval included lithium ion loss and negative material loss.Combined with the characteristics of battery cycle life,an optimization strategy for parallel operation of different types of energy batteries considering the SOC interval and rate of energy battery was proposed.(3)The energy management strategy of variable filter time constant power allocation considering cycle life of energy cells and grid-connected power volatility was proposed.The battery capacity allocation strategy considering battery charging and discharging efficiency,DC/AC converter efficiency and DC/DC converter efficiency was proposed.The power allocation of energy-only battery,the power allocation of constant filter time and the power allocation of variable filter time constant were compared and analyzed by taking wind farm energy storage as an example.The simulation results showed that the optimal energy management strategy can not only give full play to the high power characteristics of power batteries,but also control the SOC of energy batteries within a certain range to avoid overcharge or overdischarge of battery,thus prolonging its service life.There are 55 figures,7 tables and 88 references in this thesis. |
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