| In order to alleviate the pressure of power grid frequency regulation caused by large-scale renewable energy connected to grid and inadequate frequency regulation capability of traditional thermal power units under the new situation,it is urgent to seek new frequency regulation resources and means.With the continuous development and maturity of energy storage technology,it provides an important idea for power system frequency regulation.It is of great significance to study and clarify the mechanism,access mode,control strategy and capacity allocation method of energy storage participating in frequency regulation.In this paper,the load-side flexible energy storage system and the generation-side battery energy storage system participating in frequency regulation are studied respectively.The control strategy of electric vehicle access to power grid and capacity allocation optimization of energy storage in thermal-storage frequency are mainly studied.The main research contents are as follows:(1)Large-scale cluster electric vehicles,as representatives of load side energy storage,participating in frequency regulation can improve power system frequency stability.It can be used as an effective means to alleviate the frequency regulation pressure.The frequency regulation auxiliary service framework of load side electric vehicles connected to the power system is proposed,which includes the grid scheduling layer(GSL),the distributed access layer(DAL)and the centralized control layer(CCL).The electric vehicles charging mode is clarified and frequency regulation model is established.The CCL regulation pattern is cleared and the DAL electric vehicles Control Strategy is established according to CCL time spent of frequency regulation service,equivalent state of charge ratio,and its up and down capacity.The results of MATLAB/SIMULINK shows that after participation of CCL,the frequency response is more rapid and regulation capability is significantly improved.(2)Participation of energy storage in power system regulation can reduce ramping costs of thermal power unit and improve frequency stability of power system.The scheduling framework of generation-side energy storage participating in frequency regulation and the scheduling strategy of energy storage under different power structure are proposed.Meanwhile,reasonable allocation of energy storage capacity based on area frequency regulation requirements helps to improve economy and stability of system.According to historical typical area control error(ACE),an optimized capacity allocation model of energy storage was established based on ensemble empirical mode decomposition(EEMD)method.Taking into account state-of-charge constraints of energy storage system,the optimal filter order of ACE signal is determined based on EEMD method with the goal of maximizing net benefit expectation.Then the optimal capacity allocation of energy storage in frequency regulation is also determined.And effectiveness of proposed method is verified based on measured ACE data.(3)Relying on the demonstration project actual operation data of megawatt-level energy storage system auxiliary thermal power unit participate in frequency regulation,taking the grid dispatching side as the main body,explore the influencing factors of frequency regulation effect in thermal-storage combined frequency regulation mode.Firstly,the K-means clustering method is used to three-dimensional clustering the data of two power plants frequency regulation response time,adjustment rate and adjustment precision,and influence of different energy storage control methods on the frequency regulation is explored.Secondly,the nine energy flow state eigenvector are determined,and K-means clustering is used to single power plant data,to explore the thermal-storage combined frequency regulation effect under different energy flow states.The results show that different energy storage control methods directly affect the frequency regulation performance,and the change of energy flow state can reflect the frequency regulation performance in a single power plant to some extent.Accurately tracking of energy storage and energy flow state are important factors affecting thermal-storage combined frequency regulation performance. |
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