Study On The Method Of Participation Of The Thermal Power Plants-Energy Storage Systems Integrated System In Primary Frequency Regulation

With the increasingly serious problems of environmental pollution and resource tension caused by the massive consumption of fossil energy sources such as coal,renewable energy sources such as photovoltaic and wind power are connected to the power grid on a large scale,which effectively reduces carbon emissions and relieves resource tension while also bringing new pressure on the frequency stability of the power system.With the rapid development of energy storage technology in recent years,the advantages of energy storage such as fast speed,high accuracy and flexible control make its role in the frequency stability of power grid is paid more and more attention by scholars,so how to design the control strategy of energy storage to participate in primary frequency regulation is especially important.Meanwhile,although the proportion of thermal power units decreases due to the rise of renewable energy in the grid,it is still the main means of frequency regulation in the grid,so using energy storage to assist thermal power units in primary frequency regulation to equivalently improve the primary frequency regulation capability of thermal power units is the most direct and effective means of energy storage at present,therefore,this paper conducts an in-depth study on the control strategy of energy storage to assist thermal power units in primary frequency regulation,and the main results achieved are as follows:Firstly,based on the basic principle of primary frequency regulation of power system,the equivalent models of thermal power unit and energy storage suitable for designing primary frequency regulation control strategy are established,in which the thermal power unit model is more specific and can fully reflect the working characteristics of thermal power unit when participating in primary frequency regulation,so as to find the deficiencies that need to be compensated by using energy storage and accurately improve the frequency regulation performance of thermal power unit;while the energy storage is selected from the simpler control structure of A simplified equivalent model that mainly describes the external characteristics of energy storage when participating in primary frequency regulation is used;the primary frequency regulation demand of thermal power units is analyzed under two different scenarios,and it is obtained that thermal power units need to improve their own response speed in the event disturbance scenario,while the response of thermal power units to the high-frequency component of frequency fluctuation needs to be reduced in the load fluctuation scenario.Secondly,the thermal power plants-energy storage systems(TPP-ESS)integrated system is proposed as a control strategy for using energy storage to assist thermal units to participate in primary frequency regulation,and the structure of the TPP-ESS integrated system is briefly explained;the control strategy of the TPP-ESS integrated system is designed under two disturbance scenarios respectively to realize different frequency regulation demands of thermal units;the TPP-ESS integrated system-based storage state of charge(SOC)recovery control strategy based on the integrated thermal-storage system is proposed,which can achieve periodic recovery of energy storage SOC without affecting the normal frequency regulation process of the system;theoretical analysis and simulation results show that the proposed TPP-ESS integrated system can speed up the primary frequency regulation response of thermal units,improve the frequent operation of the primary frequency regulation function of thermal units caused by high-frequency load fluctuations,and maintain the energy storage SOC level.Finally,a capacity assessment method is proposed for the TPP-ESS integrated system.By extracting the evaluation indexes that can fully characterize the primary frequency regulation capability,and analyzing the relationship between the indexes and the physical parameters and operation status of the system,the capability boundary of energy storage and thermal power unit is obtained;through the equivalent frequency change curve,the output curve of the ideal output system and the output curve of the thermal power unit under the limitation of the capability boundary can be obtained,and then the power and energy deficit of energy storage that needs to be replenished can be compared with its capability boundary.By comparing with its capacity boundary,we can determine whether the TPP-ESS integrated system has the primary frequency regulation capability to achieve the ideal power contribution index.Theoretical analysis and simulation results show that this capacity assessment method can effectively assess the capacity of the integrated system and can be used as a method for energy storage selection.