Decentralized Voltage Control And Optimization In Active Distribution Networks

The large scale of distributed energy sources alters distribution networks from passive to active with bi-directional power flow,and brings challenges to conventional operation and control mode of electricity distribution networks,especially voltage fluctuations and overloading.Moreover,the increasing controllable resources and the diversified components in distribution networks make centralized coordinated control methods inapplicable for active distribution networks.This thesis focuses on distributed coordinated control in active distribution networks.The main work of this paper is fourfold as follows:1)A novel distributed voltage control strategy is proposed employing a multiple agent system(MAS)platform,which can achieve the global voltage control with renewable energy generation maximization.Each agent monitors and controls one sub-network of the distribution networks.By utilizing local measurements and communications,the proposed voltage control strategy can realize the overall network voltage management and optimization simultaneously.Compared to the centralized strategies,the proposed strategy divides a multi-dimensional calculation problem into several low-dimension calculation sub-problems,releasing the calculation burden and increasing the calculation speed significantly.2)A fully decentralized voltage control method with various multiple-microgrid participators based on MAS is proposed in this paper.Peer agents coordinate to calculate voltage sensitivities by local and neighborhood measurements only.Then,distribution system operators define an incentive mechanism to motivate independent microgrids in distribution networks to participate in voltage control.Based on the incentive,microgrids participate in voltage control as ancillary service providers while maximizing their own profits.The proposed method utilizes microgrids to provide voltage supports,which realizes flexible utilization of resources and improves energy utilization.Furthermore,in the bidding process,the game model with imperfect information is applied to protect the privacy of each player,guaranteeing the fairness and competitiveness among participants.3)A distributed coordinated control method based on measurement data of distribution phasor measurement units(DPMU)is proposed.Based on DPMU measurement data of part nodes,unknown network bounded by DPMUs is equivalent and simplified.Then,a fully distributed control strategy utilizing MAS is employed to control voltage in a fully decentralized way during voltage excursions,and to optimize network losses by balancing reactive power locally if no voltage excursions occur.In the proposed method,with lack of impedance information,DPMUs are installed at only a small portion of nodes in distribution networks,which is economic and practical.