Research On Power Grid Frequency Modulation Based On Battery Energy Storage

The output power of intermittent energy sources such as wind power and solar photovoltaic power generation has volatility and uncertainty,and does not have the inertial response characteristics of traditional power sources,which will seriously threaten the stable operation of the power system,making the traditional frequency modulation method in response to the frequency mutation of the system appear to be a bit of a problems.When large-scale new energy is connected to the grid for power generation,if the impact load disturbance occurs,together with slow response and low ramp rate of conventional FM power sources,it will be difficult to fully meet the demand of power system frequency modulation,which has become one of the main constraints of largescale intermittent energy grid connection.Therefore,the great challenge China’s power grid facing is how to ensure the safe and stable operation of power grid with the increasing new energy generation.Since the beginning of the 21th century,due to the extensive application of various energy storage technologies in the field of power system frequency modulation as well as the rapid development of frequency modulation technology,a new technological spring has been ushered in for improving the frequency fluctuations of power grid caused by intermittent energy grid connection.The application of energy storage battery system to the field of power grid frequency regulation can realize the fast and accurate tracking of power grid frequency through its stable active power output,which makes it become the research hotspot in the field of power grid frequency regulation in the world at present.In this paper,firstly the shortcomings of wind power participating in grid frequency modulation are verified.From the perspective of avoiding secondary frequency drops,the need for of energy storage battery to assist frequency modulation is identified,control methods are explored,and the control strategy is optimized.In addition,on the basis of the actual data,the effectiveness of the control strategy and the advantages of energy storage battery in assisting frequency modulation are examined.The main research content is as follows:1.First of all,the principle of the primary and secondary frequency modulation and FM capacity requirements of the power system are expounded,The IEEE three-machine nine-node system is used as the power grid model suitable for the applications of frequency modulation,and the simulation model is built on the MATLAB/Simulink software platform.Then the simulation model for the wind farm participating in power grid frequency modulation is set up.Based on actual data,the shortcomings of wind power participating in power grid frequency modulation is verified,providing research background and theoretical foundation for the future in-depth study of energy storage battery system assisting wind power in power grid frequency modulation.2.Based on the Buck/Boost bidirectional DC/DC charge-discharge circuit principle of lithium iron phosphate battery,the simulation model is set up for the charge and discharge of energy storage battery,and the main circuit structure of inverter based on the lithium iron phosphate battery suitable for frequency modulation applications is given.Besides,on the basis of the mathematical model of the lithium iron phosphate battery converter,a frequency modulation optimization control strategy for energy storage battery system is designed,which combines VSG control strategy with MPC direct power predictive control strategy.Furthermore,with the actual data as the background,the effectiveness of the control strategy is verified and the principle of SVPWM is illustrated.Finally,the frequency response effects of traditional power units,wind turbine and energy storage auxiliary wind turbine participating in the primary frequency modulation are simulated and compared.The research results show that the energy storage battery system has obvious advantages in participating in power grid frequency modulation because of effective control strategy and good control effect.