| With the increasing scale of new energy installations year by year,new energy represented by wind power has been rapidly developed.In order to reduce the impact of large-scale grid connection of new energy on the frequency stability of the power system,the safe,fast,and precise control characteristics of lithium battery energy storage systems can be fully utilized to achieve the stable and fast regulation effect of wind storage systems assisting traditional thermal power units in improving grid frequency.Therefore,studying the control strategy of wind storage systems to achieve different rates of charging and discharging based on the state of charge to achieve safe and fast primary frequency regulation of combined thermal power units is one of the core key issues in the development of future power system frequency regulation applications.The following work has been done on this article:This article first compares the advantages and disadvantages of electrochemical models,black box models,and equivalent circuit models,as well as the differences between various equivalent circuit modeling methods such as second-order RC;Then,the Sanyo 18650 GA lithium battery was used as the experimental object to obtain HPPC experimental data under different states of charge.The extended Kalman EKF filter and ampere hour integration method were applied to achieve joint state of charge SOC estimation for the lithium battery.At the same time,the least squares method was used to identify the relevant parameters of the model.A second-order RC equivalent circuit simulation model was built based on MATLAB/Simulink,The simulation model has been verified to have high accuracy based on SOC and terminal voltage output waveforms.Then,this article completed the construction of a 1MW/0.5MWh energy storage system model based on a single lithium battery simulation model through series and parallel connection,and implemented a Simulink system simulation structure for the joint energy storage system of a 10 MW traditional thermal power unit and a 5MW wind power unit to participate in primary frequency regulation;By applying fuzzy control rules to convert inputs such as wind speed and frequency slight increase into virtual inertia coefficient Kp and droop control coefficient Kd,the output frequency and power waveform of various combination conditions under different wind speeds and different states of charge were compared and analyzed.The influence of wind speed on the primary frequency regulation process of the wind storage system was analyzed,and the effectiveness of the primary frequency regulation control strategy considering wind speed was verified.Finally,this article proposes a wind storage system combined with thermal power units to participate in primary frequency regulation control strategy,taking into account the fast charging and discharging characteristics of lithium batteries.Divide the state regions of the lithium battery energy storage system and develop relevant charging and discharging priority control strategies;By combining the continuous characteristics of the sigmoid function,the optimization of the charging and discharging coefficient m of the lithium battery energy storage system is achieved,and simulation experimental waveforms such as frequency,power,and current are obtained under different SOC and wind speed conditions;A comparative analysis was conducted on the simulation results before and after taking into account the charging and discharging rate,verifying the effectiveness and correctness of the proposed wind storage system combined with the traditional primary frequency control strategy for thermal power units,laying a theoretical foundation for the application of related engineering technologies. |
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