| With the rapid development of China’s national economy,the social demand for electricity consumption is increasing,and the stability of the power grid operation is more and more demanding.But at the same time,the large-scale integration of new energy power generation into the power grid,its characteristics of volatility and randomness will bring many negative effects on the safe and stable operation of the power system.The frequency modulation of China’s power system is mostly dependent on thermal power units and hydropower units.Under the policy of "carbon neutral" vigorously implemented by the state,the proportion of installed capacity of thermal power units will gradually decrease,and it has the disadvantages of long response time lag and low climbing rate.The frequency modulation performance of hydroelectric units is superior,but limited by geographical and climatic conditions,it cannot be used as a stable and reliable frequency modulation power supply throughout the year,and the pressure of frequency modulation of the power system increases year by year.With the continuous development of battery energy storage technology,more and more attention has been paid to the application of large-scale battery energy storage devices in the frequency modulation of power grid.Although battery energy storage cannot generate power continuously like thermal power and hydroelectric power,it has the advantages of fast response rate and accurate command tracking,which forms a complementary advantage with thermal power units.In this paper,in-depth research has been done on the participation of battery energy storage in primary frequency modulation and secondary frequency modulation.The main work and achievements of this paper are as follows:(1)Firstly,the principle of primary and secondary frequency modulation of power system and the characteristics of various types of energy storage batteries are summarized,and the operation structure of the battery energy storage system is analyzed.The simulation models of battery energy storage,generator,turbine and load are established in Digsilent/ Powerfactory software.Battery energy storage adopts droop and virtual inertia control for primary frequency modulation,and virtual synchronous generator control for secondary frequency modulation.(2)In this paper,an adaptive control strategy of battery energy storage and conventional unit participating in primary frequency modulation is proposed.The droop coefficient is adjusted according to different frequency states,the output is adjusted according to the feedback of SOC,and the strategy of timely participating in and quitting frequency modulation can reduce the output to maintain the SOC when the frequency state is good.When the frequency state deteriorates,the energy storage timely participates in frequency modulation to improve frequency fluctuation.(3)Aiming at the problem that the secondary frequency modulation control method based on the regional control demand will inhibit the response speed of the energy storage battery,this paper proposes a secondary frequency modulation control method based on linear active disturbance rejection control,and the output signal of the linear active disturbance rejection control is carried out.High-low frequency division,the high-frequency signal and part of the low-frequency signal are handed over to the battery energy storage to take advantage of the fast response of the battery energy storage.(4)In view of the above control strategies,single-region and three-region power grid models are built,respectively.Simulation analysis is carried out under two cases of step load disturbance and continuous load disturbance,and the effectiveness of the above control strategies is verified. |
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