| At present,large-scale grid connection of new energy has become one of the key ways to solve the problems of global resource shortage and climate change.However,this kind of new energy does not have the inertia and damping characteristics of traditional units,and its output has weak inertia,randomness and uncertainty,which weakens the stability of power system frequency operation and increases the difficulty of frequency regulation.Traditional frequency regulation power supply has been unable to meet the increasing demand for frequency regulation,so it is urgent to introduce more high-quality frequency regulation resources.Electrochemical energy storage technology has developed rapidly in recent years,and its materials and production costs have been greatly reduced.Battery energy storage technology has been applied more and more widely in the field of power grid frequency regulation.Battery Energy Storage System(BESS)has the advantages of fast response,large capacity,bidirectional regulation and so on.It has a very good prospect in the field of power grid frequency regulation.Proper control strategy can make the effect of energy storage participating in frequency regulation better and maintain the State of Charge(SOC)of energy storage better.Therefore,the research on frequency regulation control strategy of energy storage assisted power system has certain theoretical significance and practical application value.The research content of this paper includes the following aspects:Firstly,the primary frequency regulation and secondary frequency regulation are analyzed theoretically,and the mathematical model of each part of the power system and the equivalent model of the energy storage system are established.Combined with the principle of energy storage system participating in frequency regulation,a dynamic response model of energy storage participating in primary frequency regulation and secondary frequency regulation of power system was built,which comprehensively considered the system frequency regulation demand and energy storage self-recovery,laying an experimental foundation for subsequent research.Secondly,for primary frequency regulation,this paper proposes a primary frequency regulation control strategy based on the comprehensive consideration of the system frequency regulation requirements and energy storage SOC.On this basis,the strategy of energy storage participating in primary frequency regulation is divided into two stages by taking the dead zone of energy storage participating in power grid frequency regulation as the boundary.One is frequency regulation stage of energy storage;the other is self-recovery stage of energy storage.In the frequency regulation stage outside the frequency regulation dead zone,a sagging control factor based on S function and an auxiliary frequency regulation control factor are constructed to control the charge and discharge output of BESS.The frequency regulation dead zone is the stage of energy storage self-recovery.In this stage,on the premise of ensuring that the system frequency does not fall out of the dead zone,the energy storage recovery demand coefficient and energy storage recovery limiting coefficient are constructed,which jointly determine the actual amount of energy storage self-recovery charge-discharge output.From the analysis of simulation results,it can be seen that the strategy in this paper has better frequency regulation effect when the energy storage SOC is high or low,and can better promote the recovery of SOC to the ideal state.Lastly,aiming at secondary frequency regulation,this paper proposes a control strategy of energy storage participating in secondary frequency regulation based on model predictive control.Area Control Error(ACE)signal was selected as the control signal,and ACE signal and energy storage SOC were divided into different intervals.In the sub-emergency frequency regulation area,high and low frequency division of ACE signal was carried out by empirical mode decomposition method.Under the premise of comprehensive consideration of frequency regulation requirements and SOC self-recovery,The frequency regulation task to be undertaken by BESS is obtained,and the optimal control variable sequence of BESS in the future period is determined by model predictive control,so as to determine the energy storage output depth and operation timing.Finally,the comparison and analysis of the simulation results show that the proposed method has better frequency regulation effect,and it can make full use of the frequency regulation capability of traditional units,play the advantage of rapid BESS response,maintain good energy storage SOC and improve the operation economy of the system. |
PDF Full Text Request