| With the development of social economy,the rise of new energy technologies such as wind power and photovoltaic is closely related to energy storage.Energy storage technology plays an increasingly prominent role in solving the contradiction between source and network loads.Because of its flexible configuration and fast response speed,large-scale energy storage system can better ensure the balance and continuity of new energy power supply.As a key component in the field of smart grid,energy storage plays a more and more important role.National and local policies on energy storage have been issued frequently,and the development of energy storage has effectively driven local economic growth.Energy storage technology is about to usher in a period of rapid development.In order to ensure the safety and stability of the power grid under different disturbances,it is particularly important for the energy storage system to participate in the primary frequency modulation of the power grid on the basis of considering whether it is suitable for this frequency modulation task.This paper focuses on the analysis and discussion of the problems existing in the evaluation of the frequency modulation state of the energy storage battery pack and the comprehensive control strategy of the energy storage battery pack participating in the primary frequency modulation,and further studies these practical problems existing in the current battery energy storage participating in the primary frequency modulation of the power grid.Firstly,the principle of primary frequency modulation of traditional power grid is described in detail,the advantages and necessity of energy storage participating in frequency modulation are analyzed,and the dynamic model of each component of regional power grid participating in frequency modulation,including energy storage system,is established,which provides a model basis for optimizing the control strategy of primary frequency modulation of energy storage.Secondly,it puts forward the necessity of evaluating the frequency modulation state of the storage battery group based on the characteristic variables of the energy storage battery group.For the current requirement of the frequency modulation state,it is necessary to determine whether the power release system of the energy storage system supports the power grid or the excess power absorbed from the power grid,and the priority of the storage battery group is judged by the frequency modulation state evaluation,and then the appropriate battery pack is selected to participate in the FM.In this paper,analytic hierarchy process fuzzy comprehensive evaluation(AHP-FCE)is proposed to evaluate the frequency modulation state of energy storage battery pack,the weight ratio of factors in fuzzy comprehensive evaluation is calculated by analytic hierarchy process(AHP),the fuzzy matrix is established by using fuzzy mathematics theory,and the frequency modulation priority evaluation model of energy storage battery pack is constructed,The frequency modulation state score of each energy storage battery pack is obtained through fuzzy operation.Only the energy storage battery pack that meets the frequency modulation requirements can be put into operation.Finally,the energy storage battery data of Hunan Furong power station is selected for example analysis to verify the authenticity of the evaluation method.Finally,in order to realize the safe,accurate and fast frequency modulation of the energy storage system to the power grid,for the power demand caused by the system frequency offset,a comprehensive control strategy of energy storage assisted frequency modulation optimization considering the state of charge(SOC)and state of Health(soh)is proposed.This strategy combines virtual inertia control and virtual droop control to realize the complementary advantages and disadvantages of the two control modes.In the period of deterioration of frequency deviation,The two control modes act simultaneously to rapidly reduce the deterioration degree of frequency and reduce the peak value of frequency deviation.In the frequency recovery period,considering that the virtual inertial control hinders the frequency recovery,the virtual inertial control is locked and the droop control can effectively reduce the steady-state frequency deviation.While ensuring the frequency modulation effect of energy storage,each energy storage unit is kept in a healthy working state,so as to improve the safety and economy of the energy storage system.Finally,the primary frequency modulation model of regional power grid is established,and the effectiveness of the strategy is verified by step and continuous disturbance. |
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