Control Strategy Of Thermal Power Plant-Energy Storage Integrated System To Improve Secondary Frequency Regulation Performance

With the development of the power system,more and more renewable energy sources(RES)are added to the grid.The rapid growth of RES has alleviated the problems of energy shortage and environmental pollution,but has also brought a series of impacts to the power system.As a lot of operating experience has shown,the thermal power plants currently undertaking the main task of frequency regulation can no longer meet the requirements of speed,accuracy as well as capacity.Therefore,how to improve the frequency regulation capacity of thermal power plants and maintain the frequency stability of the grid under the condition of high penetration of RES into the grid has become a research hotspot for scholars at home and abroad.The advantages of battery energy storage in regulation speed and control accuracy and its rapid development in recent years provide a more novel and promising solution to the existing problems of modern power systems.Firstly,this paper introduces the development status of the current stage of power system,analyzes the conflict between the increase of the connection rate of RES and frequency regulation.The feasibility and effectiveness of the participation of battery energy storage system(BESS)in the field of power system frequency regulation are illustrated,and their research status and demonstration projects are summarized and introduced.Secondly,the principles related to power system frequency regulation are introduced,and the power response model of the unit is established with governor,turbine,boiler and coordinated control system as the main components.The principles and components of the BESS are introduced,different modeling methods of BESS are compared,and according to the need of this paper for secondary frequency regulation performance improvement research,the universal frequency regulation model is finally selected and the relevant module for managing the charge state SOC is established.Then,the main components and operating processes of Automatic Generation Control(AGC)are briefly illustrated,and the AGC system model suitable for secondary frequency regulation analysis is established in MATLAB/Simulink according to the demand of secondary frequency regulation,with the corresponding functions of ACE calculation and filtering,dynamic dead zone and AGC command issuance block,which are focused on in this study.Each function is verified by simulation.Finally,the characteristics of the thermal power plant and BESS respectively involved in frequency regulation are analyzed and compared,and the purpose of improving the secondary frequency regulation power response performance is achieved by establishing a thermal power plant-energy storage integrated system.An output strategy of BESS that enables the utilization of the fast response characteristics of BESS to be maximized is proposed,and the active recovery of the state of charge(SOC)is considered to ensure that the BESS participates in the frequency regulation of the power system safely and stably for a long time.Based on the theoretical analysis,the simulation model of thermal power plant-energy storage integrated system is established in MATLAB/Simulink to verify the feasibility and effectiveness of the proposed control strategy in improving the performance of secondary frequency regulation with respect to the performance indexes of AGC regulation of thermal power plants proposed in the "two rules".The innovations of this paper are:① the AGC system model applicable to secondary frequency regulation analysis is established,which can make the AGC commands received by the generator in the simulation closer to the actual situation and provide favorable simulation conditions for secondary frequency regulation research and AGC performance evaluation.②the thermal power plant-energy storage integrated system is established by comprehensively considering the characteristics of thermal power plants and BESS in frequency regulation,which control the BESS output based on the change of combustion rate.③ the SOC active recovery strategy based on dynamic dead zone is added to ensure the safe and stable operation of BESS and effectively reduce its capacity allocation requirements on the basis of improving the secondary frequency regulation performance.