Research On Wind-storage Combined Frequency Modulation Control Strategy Considering Mode Switching

Frequency is one of the most important indicators for evaluating power quality,and grid frequency regulation plays an important role in maintaining stable operation of the power system.With the increasing support for renewable energy and the continuous increase of grid-connected capacity of intermittent power sources,wind power systems and energy storage systems have broad prospects for participating in grid frequency regulation.Considering the different characteristics of wind power frequency modulation and energy storage frequency modulation,how to coordinately control the energy storage system and wind turbines to participate in the frequency modulation of the power grid to obtain a better frequency modulation effect has become the focus of current research.The main research work of this paper is as follows:Based on the relevant theory of power system frequency regulation,the principles of inertial support,primary frequency modulation,and secondary frequency modulation of traditional power systems are analyzed.When the balance between the load side and the power side is broken,the possible impact on the system frequency is explained.The mechanism of frequency regulation of conventional power generating units and wind energy storage participating in frequency regulation is analyzed.Based on the analysis,the construction of the frequency response model of the power system in the wind power storage frequency modulation link is completed.Based on the method of parameter sensitivity analysis,the influence of two different frequency modulation modes of wind power inertial frequency modulation and energy storage droop control frequency modulation on the frequency characteristics of regional power grids is analyzed in terms of the initial frequency deviation change rate,the maximum value of the frequency deviation,and the steady state frequency.In addition,a control coefficient setting method considering frequency index is proposed,and simulation experiments are performed according to the parameters of an actual power grid and the frequency modulation index requirements to verify the effectiveness of the proposed method.A frequency modulation control strategy considering wind energy storage mode switching is proposed.The sensitivity coefficient characteristics of the control coefficients for wind power inertia control and energy storage droop control are analyzed.Based on the analysis,the timing of switching between the two control modes is determined.Combining the output characteristics of wind power and energy storage frequency modulation,a mode switching frequency modulation control strategy considering the output characteristics is proposed.Through simulation experiments,the frequency modulation effects of different wind storage joint frequency modulation control strategies are compared.Quantitative evaluation method of frequency modulation index based on margin analysis is used to evaluate the frequency modulation effect,and the effectiveness of the proposed frequency modulation strategy is verified.