Research On Control Strategy Of Battery Energy Storage System Participating In Primary Frequency Regulation Of Power System

With the deepening of the energy system clean transformation strategy,the proportion of clean energy in China is gradually increasing.Among them,the clean energy represented by wind and solar energy is gradually replacing the traditional fossil energy,and the power sys tem is gradually showing the characteristics of ‘high proportion of renewable energy penetration’.However,the randomness and volatility of clean energy power generation will lead to intensified power fluctuation at the power supply side,which brings great challenges to power system frequency regulation.Therefore,it is urgent to introduce a new frequency modulation method to alleviate the frequency modulation pressure of thermal power units.Battery energy storage system（BESS）,as an effective means to solve the grid connection of clean energy,has attracted much attention in the field of primary frequency regulation（PFR）due to its advantages of accurate tracking,fast response,high control accuracy and bidirectional regulation ability.Reasonable control strategy can make BESS more efficient and more economical to participate in the PFR of power system.Therefore,the research on the control strategy of BESS participating in the PFR of power system has important theory meaning and engineering value.The main research contents are as follows:The basic principle of PFR of power system is analyzed,and the PFR model of traditional power system is established.According to the technical and economic indicators of energy storage,the applicability of different kinds of energy storage to participate in the PFR of power system is evaluated,so as to determine the selection of lithium-ion battery to participate in the PFR of power system.On this basis,the equivalent model of BESS considering charge-discharge efficiency is constructed.Combined with the PFR model of traditional power system and the equivalent model of BESS,the PFR model of power system with BESS considering charge-discharge efficiency is established,which provides the foundation for the verification of the proposed strategy in the following.In order to solve the issue of insufficient charging and discharging frequency regulation capability of BESS when state of charge（SOC）is low or high,an integrated control strategy of energy storage for PFR based on frequency regulation coefficient of BESS and SOC recovery is proposed.The strategy divides the PFR of energy storage into energy storage frequency regulation stage and energy storage SOC recovery stage according to the upper and lower limits of energy storage frequency regulation dead zone.In the frequency regulation stage,based on S-type function,the construction method of auxiliary frequency regulation control and the calculation method of frequency regulation coefficient of BESS are put forward,and the power system frequency is controlled by frequency regulation coefficient of BESS.In the SOC recovery stage,the output strategy of SOC recovery is constructed,which considers the demand of SOC recovery and the limitation of power system operation state comprehensively.Based on the Matlab/Simulink simulation platform,the PFR model of power system with BESS considering charge-discharge efficiency is built.On this basis,the necessity of considering charge-discharge efficiency in the PFR model of power system with BESS is verified.The effectiveness and superiority of the integrated output control in the frequency regulation stage and the output control in the SOC recovery stage are verified by the control variable method under step and continuous load disturbance conditions.