Research On Optimal Allocation Of Solid State Transformer In Active Distribution Network

Based on the speedy development of power electronic technologies,power electronic translation device,as a key device that can provide AC/DC power distribution form conversion,distributed generation(DG)access control and other functions,has gradually become the core device in the active distribution networks(ADNs).Solid state transformers(SSTs)based on fully controlled power electronic devices,not only have the basic functions of traditional transformers,such as power transmission,voltage transformation and electrical isolation,but also have the ability of flexible regulation,such as active/reactive power regulation,voltage control and harmonic control.At the same time,SSTs can realize the interconnection of different distribution subnetworks,providing technical support for the traditional ADNs to the complex AC-DC hybrid ADNs.Focuses on the topics of the planning method of SSTs,the core contributions of the thesis are summarized as follows:1)An equivalent operation model of multi-port SSTs in AC-DC hybrid ADNs is proposed in this thesis.The port control parameter equation is obtained considering different control modes of different ports.Different access methods of SSTs in ADNs with different port combinations are discussed to provide theoretical support for the research on optimal configuration of SSTs in ADNs.2)In view of the running-planning joint optimization problem,considering the time-series multi-scene operation model of DGs,the original invasion weed optimization(IWO)algorithm was improved in the aspect of search strategy and calculation structure.A bi-level master-slave modified IWO algorithm was proposed for the multi-scene running-planning model.The SSTs double-layer optimal allocation model in AC ADNs is used to verify the rapidity and convergence of the proposed algorithm.3)Considering the problem of SSTs replacing traditional transformers and the coordinated operation of active/reactive power in ADNs,a bi-level optimal configuration model of SSTs is established.Considering the different access methods of SSTs in AC-DC ADNs and the coordinated operation of active/reactive power in ACDC ADNs,a bi-level optimal configuration model of SSTs was established in AC-DC ADNs.Considering the mutual influence between SSTs and DGs in AC-DC ADNs,a bi-level coordinated optimal configuration model of SSTs and DGs was established.The proposed optimal models are tested on different ADNs scenarios to determine the configuration results of SSTs and good economic benefits are obtained.