Research On Integrated Control Of Primary Frequency Regulation Considering Dead Band Of Energy Storage

With the increasing of energy shortage,new energy grid-connected and energy storage technology have become an important part of the future energy strategy.The capacity of China's total wind power generation installation ranks the top in the world,however wind curtailment is too much due to the limitation of power grid absorptive capability.Nearly 30% of wind curtailment is caused by frequency regulation.In recent years,a large number of commercial energy storage projects have been applied in the ancillary services at home and abroad,which makes the demand and control strategy of energy storage PFR(Primary Frequency Regulation,PFR)become the current research hotspot.The main purpose of energy storage participating in frequency regulation on one hand is to assist conventional power supply to improve the effect of system frequency regulation;on the other hand,taking advantage of its fast power throughput capacity to reduce the loss of conventional units participating in frequency regulation,thus the economy of conventional power frequency regulation function can be improved.Starting from the main purpose of energy storage participating in power grid frequency regulation,this paper studies the action boundary limitation of energy storage,the selection of energy storage mode and the design of energy storage output constraint respectively.Considering the SoC(state of charge,SoC)of energy storage,and maximizing its utilization,a comprehensive control method of energy storage participating in primary frequency regulation of power Grid which considering the dead zone of frequency regulation as well is proposed in this paper.This paper expounds the comprehensive static power-frequency characteristics of power system,and analyses the principle of PFR and load frequency deviation response of conventional units.Based on the speed regulation system of thermal power units and the transfer function of single reheat series compound turbine,the frequency response model of traditional thermal power units participating in PFR of power grid is constructed.The demand of battery energy storage power supply participating in PFR of power grid is analyzed.On the basis of the equivalent circuit model of battery energy storage system and considering the charging and discharging efficiency model of battery energy storage,a regional simulation model of battery energy storage power supply participating in PFR of power grid is created,which provides a simulation model foundation for the theoretical verification in later chapters.In order to take the biggest advantage of the potential of fast and accurate energy storage response in power grid frequency regulation,the dead-zone limitation of energy storage participating in frequency regulation is defined by analyzing the dead-zone mechanism of conventional units.The dead-zone limitation of energy storage in frequency regulation is set within the dead-zone range of conventional units,which can effectively improve the quality of power grid frequency and avoid the frequent action of conventional units participating in frequency regulation.By analyzing with the effect of VIC(Virtual Inertia Control,VIC)and VDC(Virtual Droop Control,VDC)on power grid frequency,an adaptive control method based on logistic function and SoC constraints is proposed,which takes into account the energy storage affected by the dead-zone of action to participate in PFR.According to the requirement of frequency regulation,the control strategy of energy storage output can be selected automatically to realize the coordinated operation and complementary advantages of the two control strategies.In order to constrain the output of energy storage power,the adaptive control law based on logistic function is adopted for VIC and VDC to avoid the depletion or saturation of SoC.A simulation model of PFR for typical regional power grid based on the simulation platform of MATLAB/Simulink is built.The simulation experiments are carried out to verify the proposed method in this paper.The control variable method is used to make a systematic comparison and analysis between the proposed method and the mainstream methods in literature from three aspects: dead-zone setting,control strategy selection and energy storage output constraint.The results show that this method can not only improve the effect of frequency regulation,but also significantly reduce the frequency regulation action times of conventional units,which is conducive to improving the operation economy of PFR of traditional units.