Research On Capacity Allocation And Control Strategy Of BESS Participating In Secondary Frequency Regulation Of Power Grid

With the accelerating fossil energy crisis and environmental protection issues,new energy sources such as wind power,which are random,intermittent and unpredictable,have developed rapidly in the power industry,and they have also brought more and more severe challenges to power grid frequency regulation.Conventional units have limited frequency regulation capacity,slow response,dead zone oscillation and possible reverse frequency regulation,which is difficult to meet the increasing demand for frequency regulation and restricting the ability of the grid to absorb clean energy.Energy storage batteries,as a time-scale flexible power supply,can dynamically absorb and release energy,and have fast response and high control precision;having these advantages,energy storage batteries participating in the secondary frequency regulation has become a very important method of frequency regulation.It is not only directly affecting the technical economy of energy storage participating in frequency regulation,but also affecting its popularization and application in frequency regulation market to determine the suitable revenue mode,the reasonable energy storage configuration and scientific control strategy of BESS participating in the secondary frequency regulation.This paper studies the capacity allocation and coordinated control of energy storage batteries in the secondary frequency regulation in large-scale grid-connected systems of new energy.Firstly,qualitatively analyze the static,dynamic and environmental benefits of BESS in frequency regulation;On the basis of analyzing the two widely used return models of BESS,this paper constructs the cost-benefit calculation model of full life cycle of BESS in the secondary frequency regulation considering real-time electricity,standby power and environmental benefits,which can calculate the benefit of the BESS separately.The cost-benefit model can better explain the gains of BESS in secondary frequency regulation,and can provide some support for the capacity allocation and optimal control of BESS.Secondly,based on the principle of empirical mode decomposition(EMD)and considering the limitation of ramp rate of conventional units,this paper designs an initial power instruction allocation method for BESS in secondary frequency regulation;Basing on the cost-benefit calculation model of BESS in secondary frequency regulation,which is formed above,taking the maximum net benefit as the goal,the capacity and the power as the decision variables,and considering the real-time output,the frequency regulation demand constraint and the State of Charge(SOC)boundary,the optimization configuration model of BESS is established;The process of using genetic algorithm to assist in solving the optimization model is the corresponding capacity allocation method flow.The simulation results show that the proposed initial power instruction allocation method is beneficial to better utilize the advantages of the unit and the BESS,and the proposed capacity allocation optimization model takes into account the constraint effect of the frequency regulation demand on the BESS output,which is convenient to coordinate the economic and technical requirements of the configuration scheme and enhance the flexibility of planning.Finally,regarded the energy storage battery as an independent resource in frequency regulation,a control strategy based on the priority order method is proposed to coordinate the participation of BESS and conventional units in the secondary frequency regulation.Considering the limitation of the maximum and minimum output and the climbing rate of the conventional unit,the SOC and the service life limit of BESS,this paper defines the power response capability,response time and remaining life as the secondary frequency regulation performance parameters.On the basis of the secondary frequency regulation performance parameters,the secondary frequency regulation performance indexes are established,and the initial variable output sequence table of the conventional units and BESS is formed.Then,the correction method of initial variable output sequence table based on output stability requirement of conventional units,the principle of power distribution and the blocking situation of BESS for preventing the SOC from exceeding the limit are designed,thereby the final control strategy implementation process based on the priority order method of the BESS in secondary frequency regulation is formed.The simulation results show that the proposed control strategy has feasibility and certain superiority,and compared with Shijingshan control strategy,on the basis of ensuring the frequency regulation effect,the control strategy reduces the numbers of changing the output for conventional units and BESS,which is conducive to the stable operation of conventional units and to the extension of the service life of BESS.