Research On Primary Frequency Regulation Modeling And Control Strategy Of Wind Farm-Energy Storage Combined System

In recent years,the environmental pollution caused by the use of fossil energy have become increasingly serious.Due to the non-renewability of fossil energy,energy shortage has become increasingly prominent.People are gradually studying and using clean energy.At present,the use of clean energy is mainly wind power and photovoltaic power generation.In some areas,the penetration rate of clean energy has exceeded 20%.At the same time,wind power and solar energy have strong volatility and uncertainty.Compared with the traditional thermal power unit,there are certain difficulties in scheduling,and it is hard to adjust the power grid like the conventional unit.Especially for the frequency regulation,the frequency fluctuation of the power grid can only be adjusted by the active power of the generator.Therefore,it is necessary to consider using the new energy for frequency regulation in the power grid.With the continuous advancement of wind power technology,variable speed fans have been used in large quantities,which makes wind power have certain adjustment capabilities.Therefore,wind power can be considered for frequency regulation.In addition,the flexible and fast response characteristics of energy storage contribute to the grid connection of wind power and the frequency regulation of power systems.Therefore,it can be considered to combine wind power and energy storage to form a wind power and energy storage system for frequency regulation in power system.In this paper,the primary frequency regulation of the wind power and energy storage system is studied.It aims to make the wind power can replace the thermal power unit for a frequency regulation when the wind power penetration rate is high.And by configuring the energy storage,the curtailment is reduced and the frequency regulation effect is better.Firstly,the current development of wind power and energy storage is analyzed.According to the installed capacity of wind power and the technical characteristics of energy storage,the possibility and necessity of wind power and energy storage for frequency regulation are discussed.Through simulation experiments,the influence of wind power on the frequency after connecting to the grid is explored.Then,the quartile method is combined with the proportional curtailment strategy that has been applied to dispatching,considering the coefficient of variation and a method for determining the proportion of curtailment is proposed.The primary reserve can be adjusted according to the maximum available power.Deploying an energy storage,a wind farm-energy storage system is built,and both the wind farm and the energy storage need to provide primary reserve so that the curtailment can be reduced.At the same time,using the Logistic function,a method for calculating the regulation coefficient of state of charge is put forward,which can adjust the proportion of curtailment.And taking a whole day as a scheduling period,considering the state of charge in different situations,the primary reserve of wind farm-energy storage in each state is calculated.Finally,the frequency regulation model of the wind farm-energy storage is improved and established.Considering the reserve capacity and the feedback control of energy storage,the primary frequency regulation strategy of the wind farm and the energy storage system is proposed.And the MATLAB/Simulink was used to construct a frequency-regulated simulation model,which simulated the sudden drop of load,sudden rise and multiple random load fluctuations within 500s,to verify the feasibility and effectiveness of this method.