Research On Frequency Regulation Strategy Of Battery Energy Storage In Power System

With the increasing penetration of the renewables,the number of synchronous generators is decreasing,the control areas are generally with insufficient frequency regulation capability.Battery energy storage has many advantages,such as fast response speed,high control accuracy,no geographical restrictions,strong switching flexibility and so on.Using battery energy storage to participate in frequency regulation control(FRC)has become one of the solutions to the above problems,so it has attracted wide attention.This thesis studies the related issues of battery energy storage participating in FRC.Firstly,several kinds of common battery energy storage equivalent models and traditional FRC dynamic models are summarized,the dynamic models of battery energy storage participating in primary frequency control(PFC)and secondary frequency control(SFC)of power grid are constructed respectively.In order to rationally distribute the FRC responsibility of conventional synchronous generators and energy storage,based on the empirical curve of operation loss and output power of conventional synchronous generators,the FRC loss function is defined,which is regarded as the key index of responsibility allocation.Finally,according to the technical characteristics of FRC power supply,the constraints of FRC are summarized.Secondly,aiming at the battery energy storage participating in primary FRC,the necessity of battery energy storage participating in PFC is analyzed from the angle of amplitude-frequency characteristics.By comparing the amplitude-frequency characteristic curves of regional power grids with different energy storage unit regulating power,the influence of the unit regulating power value of battery energy storage on FRC is obtained.This thesis presents a PFC strategy for battery energy storage based on dynamic coefficient,which aims at minimizing the total loss of battery energy storage in FRC.The results show that the proposed strategy can significantly reduce the frequency fluctuation of the system under severe load disturbance,rationally distribute the responsibility according to the characteristics of each battery's energy storage and ensure that SoC is near the optimal state to realize the balanced control of battery energy storage.Finally,aiming at the battery energy storage participating in the SFC,several kinds of traditional FRC method are summarized.On the basis of explaining the limitations of traditional centralized control algorithm and the advantages of distributed algorithm in power system,the distributed algorithm is applied to SFC of battery energy storage.Therefore,a SFC strategy for battery energy storage based on consistency algorithm is proposed.The objective function is to minimize the loss of FRC.The global control goal is achieved by iterating the consistency variable.The simulation results show that the strategy can reasonably allocate the responsibility of conventional synchronous generators and batteries on the basis of meeting the FR requirements of power grid.On the one hand,conventional synchronous generators respond to low-frequency SFC signals to avoid the mechanical wear caused by frequent climbing;On the other hand,battery energy storage responds to high-frequency signals to give full play to its rapid response advantages,while effectively maintaining the SoC.