| Large-scale electrochemical energy storage is considered to be a key technology to support the safe operation of a high percentage of renewable energy power systems.Large-scale energy storage realizes high-voltage,large-capacity,and large-scale applications by combining low-voltage and small-capacity battery cells through series and parallel structures.The inconsistency and time variability of the state of charge and health performance of single cells restrict the full utilization of energy storage capacity.Accurately estimating the battery status,reducing battery dispersion,and optimizing the system's operating path are the keys to achieving maximum utilization and safe operation of the energy storage system.The thesis takes 200Ah lead-carbon battery as the research object,and conducts in-depth research on the technical problems such as battery state estimation,battery performance degradation estimation and system control strategy design encountered by the battery energy storage system to suppress micro-grid power fluctuations.The main tasks are as follows:(1)State estimation of lead carbon battery based on Thevenin equivalent circuit model.Energy storage battery performance decay and operating path dependence determine its external characteristic parameters to be time-varying non-linear.Traditional estimation methods do not consider the impact of battery performance aging,resulting in poor adaptability of the battery life cycle estimation.The paper analyzes the formation mechanism of lead-carbon battery storage capacity and terminal voltage,proposes a method for identifying open-circuit voltage and resistance-capacitance parameters of lead-carbon batteries based on Thevenin model.Based on a large amount of battery charge and discharge test data,the lead that can reflect the battery performance aging characteristics is excavated.The correlation between the working voltage of the carbon battery and the available power of the battery.Based on this,a new method for estimating the state of lead-carbon batteries based on the relationship between the open-circuit voltage of the fully discharged state and the available power is proposed,realizing high-precision estimation of the state of the battery,and balancing energy storage batteries.Lay the foundation for optimal control of management and energy storage systems.(2)Balanced management of lead-carbon energy storage battery packs taking into account battery status.The dispersiveness of the performance of the single cells,the difference in the running path and the working environment lead to the inconsistency between the voltage between the series batteries and the power between the parallel batteries in the energy storage battery pack,which causes the energy storage batteries to be overcharged and discharged,and the system capacity utilization is reduced.The paper analyzes the reasons for the inconsistency of battery voltage and power,and proposes a battery balancing control strategy for parallel battery packs that considers the state of the battery,a circuit topology based on battery voltage to achieve power transfer through series flyback converters to achieve series battery voltage balancing,and can be achieved.Circuit topology for failed battery replacement online.Finally,combining battery management technology related theories,a battery management system(BMS)hardware experimental platform capable of real-time management of 108 battery energy storage systems is designed,and the design process and design concepts of the main functional components in the BMS are carried out.(3)Optimal operation control of lead-carbon battery energy storage system considering battery state constraints.In the micro-grid with renewable energy power generation and fluctuating loads,there is a problem of energy storage battery charge and discharge path optimization when the energy storage system is used to smooth the fluctuating power.The paper analyzes the source-charge fluctuation characteristics and the operating characteristics of the battery energy storage system in the microgrid.Based on the dual battery energy storage system(DBESS)charge-discharge separation operation mode,the DBESS operation balance index control storage.It can optimize the charging and discharging path of the system.Through the control of the DBESS charge and discharge path,the optimization of the DBESS battery state is realized,the coordination and flexibility of the DBESS operating state are improved,the available capacity of the DBESS is expanded,and the bidirectional adjustment capability of the battery energy storage system is enhanced. |
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