Research On Control Strategy Of Hybrid Energy Storage Participating In System Frequency Regulatio

With the continuous progress of new energy power generation technology,its installed capacity has increased significantly.However,due to its characteristics of weak inertia and instability,after large-scale grid connection,the stable operation of power system will be seriously affected,especially the frequency stability.At this time,the traditional units can not meet the demand of frequency modulation.In view of the advantages of fast response speed and high control accuracy of energy storage,using energy storage equipment for frequency modulation has become one of the methods to solve the above problems.Due to the inherent defects of single energy storage equipment,the participation of hybrid energy storage in system frequency modulation has become a research hotspot in recent years.This paper studies the control strategy of hybrid energy storage in system frequency modulation.Firstly,it summarizes the development status of new energy power generation and the impact after large-scale grid connection.Based on this background,it analyzes the necessity and feasibility of energy storage participating in system frequency modulation.Then,it analyzes and summarizes the research status of energy storage equipment participating in system primary frequency modulation and secondary frequency modulation from the aspects of control strategy and relevant policies.Secondly,by expounding the characteristics of various energy storage equipment,and comparing various energy storage equipment from two aspects of technology and economy,it is determined that super capacitor and lithium battery are the most suitable combination of frequency modulation hybrid energy storage.Then,the frequency dynamic response model of each part of the system and the simplified simulation model of hybrid energy storage are constructed respectively.On this basis,the dynamic simulation models of primary frequency modulation and secondary frequency modulation with hybrid energy storage are constructed.Then,the control strategy of primary frequency modulation of hybrid energy storage system is studied.In order to make the super capacitor charge and discharge before the lithium battery,the frequency modulation dead zone of the super capacitor is set within the frequency modulation dead zone of the lithium battery,and the specific value is determined by simulation.Then,based on the logistic function,the sag coefficient is adjusted in real time according to the state of charge(SOC)of supercapacitor and lithium battery,so that the hybrid energy storage can participate in the primary frequency modulation of the system with the dynamic sag control strategy.The simulation platform is built in Matlab / Simulink to determine the frequency modulation dead zone of hybrid energy storage.Based on the setting of frequency modulation dead zone,the effectiveness and superiority of the control strategy in this paper are compared and analyzed.Finally,the control strategy of hybrid energy storage participating in the secondary frequency modulation of the system is studied.Firstly,the first-order low-pass filter is used to distribute the low-frequency part of the regional deviation signal to the traditional unit and the high-frequency part to the hybrid energy storage.Then,according to the SOC value of supercapacitor and lithium battery,the internal distribution coefficient of hybrid energy storage is determined by fuzzy control,and the power of hybrid energy storage is distributed between supercapacitor and lithium battery based on this distribution coefficient.The simulation platform is built in Matlab / Simulink to prove the effectiveness of the control strategy in frequency adjustment effect and SOC maintenance effect.