| Under the guidance of a series of policies aimed at implementing the carbon peaking and carbon neutrality strategy,such as the clean energy structure on the power generation side,the installed capacity of photovoltaic grid-connected in various regions has maintained rapid growth in recent years.However,with the continuous access of large-scale PV,PV’s own output fluctuation and zero inertia characteristics will bring frequency safety risks to the system operation that cannot be ignored.Therefore,taking the large-scale photovoltaic access to the feeder-side power grid as the research object,the stable control effect of photovoltaic active participation in frequency regulation and other measures on the system frequency is deeply discussed on the basis of predecessors,which improves the frequency stability of the actual power grid with high photovoltaic proportion.Firstly,according to the different research objects of the topic,two types of research levels are clarified: site level and whole network level.At the site level:focusing on the sub-topic of "photovoltaic frequency modulation",the research status of three different types of photovoltaic frequency regulation technologies is reviewed.At the whole grid level,three types of regional power grids with high photovoltaic penetration and obvious sending characteristics are selected for literature research,and the main progress made in the existing literature on frequency stability control in relevant regions is summarized.Aiming at the basic unit of the research project,the photovoltaic power generation system,its basic output characteristics,conversion control strategy,filter parameter design,etc.are analyzed,and a two-stage photovoltaic system model is built to verify the aforementioned grid-connected control theory,which laid the foundation for the subsequent photovoltaic participation in frequency regulation and actual power grid modeling research.Secondly,in view of the lack of research at the site level,the effect of photovoltaic-energy storage active participation in frequency regulation on system frequency stability is discussed in depth.Based on the proposed new power system frequency response model considering the effect of photovoltaic frequency regulation,the influence of photovoltaic frequency regulation dead band and modulation coefficient on the frequency stability characteristics of the system is studied.On this basis,combined with the latest national standard,a parameter design method for photovoltaic participation in frequency regulation is proposed,which is more beneficial to new energy consumption and daily maintenance than the previous scheme.At the same time,the frequency regulation parameters of energy storage were determined by analogy with photovoltaics,and the frequency adjustment effects of photovoltaic/solar storage are compared and studied under the same working conditions.Finally,in view of the lack of research on the topic at the whole network level,the effect of various control strategies including unit frequency regulation on the improvement of system frequency stability is deeply discussed.Based on the modeling mechanism of various types of power components and the actual power grid operation mode data,the actual power grid model with photovoltaic penetration rate around 10.74%,15.93% and 20% is constructed in PSD-BPA,and the stable control effect of multiple single or coordinated control strategies on the system frequency after failure was studied.The results reflect the research conclusion of Chapter 3 "The Influence of Frequency Modulation Parameters on System Frequency Stability",and show that the proposed frequency coordination control strategy can not only reduce the amount of cutting,but also achieve better frequency adjustment effect under the premise of smaller power modulation. |
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