Decentralized Voltage Control Of Active Distribution Network Based On Soft Open Points

The increasing penetration of distribution generators(DGs)exacerbates the complicity of power flow in active distribution networks(ADNs).DGs,represented by wind turbines and photovoltaics,have significant uncertainties in spatial and temporal distribution.A series of operational problems such as rapid fluctuation of feeder power and serious voltage violation consequently appear,which threaten the security,stability and economic operation of the system.Soft open point(SOP)is a novel power electronic device in active distribution networks.Due to its flexible and accurate control of active power flow and reactive power,it has been widely applied in ADNs in recent years.Aiming at regulating voltage levels in ADNs,this thesis focuses on the decentralized voltage control with SOPs based on cone programming and sensitivity analysis.The main contributions can be summarized as follows:1)The partitioning method of ADN centered on SOP is proposed.First,electrical distance between node and SOP is defined based on network parameters.Then,a fast searching partition model is built to divide the network into several sub-areas centered on SOP.Considering the number of SOP may small to fulfill the requirement of the decentralized control,a clustering partition method named "fast search and find of density peaks" is furtherly used to determine the center nodes of sub-areas without SOP,in which nodal density is defined based on electrical distance.Both partitioning algorithms are verified on IEEE 33-node system.2)A decentralized voltage control model for SOPs in ADN based on cone programming is established.The decentralized control framework includes three steps,network partition,intra-area autonomy and inter-area coordination.After partitioning the network,the intra-area autonomy model based on cone programming is proposed.Then,with the algorithm of alternating direction method of multipliers(ADMM),the inter-area coordination model based on cone programming is built.The validity of the proposed decentralized control model is demonstrated by case studies on IEEE 33-node system.3)To further improve the efficiency of operation control,a decentralized voltage control model for SOPs based on sensitivity is proposed.Voltage-to-power sensitivity is introduced to further linearize the decentralized voltage control strategy and improve the efficiency of the optimization calculation.Case studies on the IEEE 33-node system are carried out to illustrate the effectiveness and higher computational efficiency of the proposed method.