A Two-tier Collaborative Distributed Decision-making Method For Grid Reactive Power Optimization Problems

As the size of the power grid continues to expand and the proportion of renewable power integration gradually increases,the non-linear optimization of the power grid becomes more complex,and the difficulty of centralized reactive power optimization and voltage control increases.Nowadays,the conventional method of voltage control is that energy management system(EMS)collects data,accomplishes optimal computation and generates decisions centrally.This centralized control model requires higher computing resources and information transmission performance,which restricts real-time performance of online applications and further improvement of the control efficiency.Considering on limitations of the centralized control mode,we propose a concept of a virtual soft controller(VSC),and build a two-layer management and control system architecture for distributed volt/var control which is constructed of VSC and EMS.Based on this architecture,this thesis studies distributed reactive power optimization and voltage control in distribution network and transmission network.The main work of this thesis is as follows:(1)In view of the distribution network,based on the two-layer management and control system architecture,this thesis studies how to reach the target voltage of load side and minimize the active power loss.The local decision-making scheme of VSC is designed,and a new method for distributed volt/var control of distribution network is proposed.Case study shows that the proposed method is feasible and the algorithm can efficiently generate distributed volt/var control strategies.(2)Aiming at the problem that reactive power compensation station participating in point of common coupling(PCC)voltage control of nearby wind farm,we establish index collection,including drainage ratio of increment of reactive power,the guarantee degree of reactive power supply,and the degree of voltage support.A scheme for screening candidate substations is given.Based on the two-layer management and control system architecture,a new method for distributed PCC voltage control in transmission grid is proposed.Case study shows that the decision results provided by the proposed method can accurately restore the PCC voltage to the set target with the substations' assistance.(3)In view of voltage control in transmission grid,combining the above research,the thesis proposes two distributed voltage control methods respectively based on electrical dissection information and sensitivity information.Case study shows that the decision results provided by the two methods can accurately restore the voltage to the set target with the substations' assistance.