Study On Control Strategy Design Of Battery Energy Storage System For Power Grid Frequency Regulation

It is a significant measure for the low-carbon energy transition to make a great effort on the development of wind power.Based on the maximum power point track operation mode,wind power control system can not respond the variation of frequency with increased large-scale wind power being centrally connected to the grid,power systems with high wind power penetration are facing a severe frequency regulation issue.The energy storage system has become a new method for frequency regulation of power grid because of its fast response characteristic and accurate tracking characteristic.Due to the expensive cost of energy storage and the defect of compensation mechanism in the present situation,if the upfront investment,construction and operation of the energy storage are borne by the developer,and owners only provide site and grid access,then,it will be hard to get profit.Therefore,the enthusiasm of energy storage for power grid frequency regulation has not been aroused.Optimizing continually operation-control strategy to improve economic benefit becomes a current research focus.This subject has carried on comparatively systematic research around energy storage capacity allocation,control strategy design and economic evaluation for the grid under high wind power penetration.Firstly,based on various energy storage systems' techno-economical features,the applicability evaluation index system of energy storage for frequency regulation is established.Further,by the objective-subjective weighting method,four kinds of energy storage technology for lithium battery,lead carbon battery,vanadium redox flow battery and flywheel energy storage are selected,which are suitable for frequency regulation of power grid.Then,based on the working mechanism and typical parameters of the four energy storage systems,the equivalent circuit model is established.The frequency regulation characteristics and capabilities of four energy storage systems are studied.This provides the basis for the design of the follow-up control strategy and the establishment of the simulation model.Secondly,this subject has studied a preliminary capacity configuration method of the battery energy storage system for frequency regulation.Further,a control strategy with considerations of virtual inertia response and combined droop control is designed.This strategy can adjust dynamically droop coefficient based on SOC of the energy storage,and take into account frequency regulation effect and SOC retention.By simulation analysis in the case of large disturbance and normal load fluctuation.The simulation results show that the proposed control strategy can reduce the transient frequency deviation and steady-state frequencydeviation,shorten the recovery time and improve the SOC retention rate of the energy storage system.Finally,a cost accounting method which can maintain balance between income and expenditure is established,Then the average annual cost and the cost of per kilowatt-hour cost of four kinds of energy storage technology are analyzed and compared.A energy storage technology which are most suitable for frequency regulation of power grid is selected.Economic modelling of energy storage for power grid frequency regulation based on Integer Programming is established.The optimal capacity of energy storage to maximize the net benefit is calculated when unit energy storage cost drops to profit turning point.This article research regarding arouses enthusiasm of energy storage for frequency regulation to have certain value,and it can speed up the building of compensation mechanism for frequency regulation.