| Power generation from new energy,represented by wind and solar energy,has been developing rapidly in recent years.Due to its fluctuating and uncertain power output,large-scale integration of new energy will pose a series of new challenges to the safe and stable operation of power systems.Traditional power supplies,such as thermal power plants and hydropower stations,constrained by their ramp rates and response speeds,getting more and more difficult to cope with power grid frequency problem after large-scale integration of new energy.How to ensure frequency stability of power grids containing high penetration of new energy power generation has become one of the major challenges that power grids face.Battery energy storage system(BESS),because of its fast response,large short-time power throughput and flexible control characteristics,has been regarded as the most promising auxiliary frequency regulation means and has got the extensive attention of academic and engineering circles in recent years.Therefore,application of BESS in secondary frequency regulation is researched in this paper,from aspects of application scene mining,optimal capacity configuration and efficiency analysis.Firstly,the basic principle and existent problems of secondary frequency regulation is introduced;taking the operation data of actual power grids as an example,5 application scenes demanding BESS to participate in secondary frequency regulation(i.e.,3 emergency scenarios including start-stop of pumped storage power stations,direction contradiction between primary and secondary frequency regulation,and heat storage shortage of thermal power generating units when conducting primary frequency regulation,and 2 daily automatic generation control(AGC)operation scenes including big tracking deviation between the output of traditional power supplies and area control error(ACE)instructions,and high frequent actions of traditional power supplies under ACE instructions),in order to expound the necessity of BESS to participate in power grid frequency regulation.The feasibility of BESS to take part in power grid frequency regulation is also expounded,from the aspects of technical and economic performances,and industrial development;based on the regional equivalence method,a frequency regulation equivalent model of the regional power system containing BESS is established.Secondly,from the angle of power grid frequency regulation service providers,a capacity configuration method for obtaining the maximum net benefit is proposed for BESS based on empirical mode decomposition(EMD).This method conduct EMD to ACE signal,and assigns the decomposed high frequency components to BESS;according to the calculation results of an established technical and economic model of BESS participating in secondary frequency regulation,an signal allocation method that brings about the maximum net benefit is selected,and the corresponding BESS capacity is obtained.The validity and superiority of the proposed method are verified by the ACE signal generated from the disturbance data of a real power network.Finally,from the angle of frequency regulation capacity,a method for evaluating the efficiency of BESS participating in secondary frequency regulation is proposed.Two modes of BESS participating in secondary frequency regulation are introduced,that is,the mode receiving ACE signal and receiving area regulation requirement(ARR)signal;a comprehensive evaluation index of frequency regulation performances is designed,and efficiency multiples of BESS are defined as the ratios of capacities of traditional frequency regulation units to BESS;based on the frequency regulation dynamic model of regional power system containing BESS,the efficiency degrees of BESS under the two participation modes in the step disturbance and continuous disturbance conditions are simulated and analyzed.This method provides a certain reference to the cognition and evaluation of the value of BESS in the application of power grid frequency regulation. |
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