State Estimation And Day-ahead Schedulin Model For AC/DC Distribution Network

With the rapid development of power load demand,it is difficult for traditional AC distribution networks to maintain power supply for higher power density in the future.It is difficult to meet the contradiction between increasing load and insufficient power transmission corridors,and it is difficult to achieve high reliability and high quality power supply.Traditional AC distribution networks are facing an unprecedented challenge.In recent years,with the continuous maturity of flexible DC technology,the operational reliability of flexible DC technology has been improved year by year,and the construction cost has been greatly reduced.At present,it has been successfully applied in distribution network,and the advantages of high proportion absor:ption of new energy in DC distribution network have gradually emerged.At the same time,the power supply and load with DC characteristics continuously connected on the power supply side and the load side are constantly driving the development of the DC distribution network.Considering the current large number of AC distribution lines and loads,AC/DC hybrid distribution networks can effectively compatible and manage AC and DC heterogeneous loads and complex power supplies,which will be a new direction for the development of distribution networks in the future.In this context,this paper considers the need for state estimation and optimal scheduling strategy for AC/DC hybrid distribution networks with flexible DC,combined with quadratic constrained quadratic optimization and second-order cone optimization,in the state estimation and optimization scheduling strategy method.The main work of this dissertation can be summarized as follows:1)Based on the existing research,the characteristics of AC/DC hybrid distribution network are expounded.And the voltage level,interconnection requirements and morphological characteristics of the AC/DC hybrid distribution network in China are briefly introduced.In addition,the current introduction of AC/DC hybrid distribution network is briefly introduced.The research status of network state estimation and optimization scheduling summarizes the development status and practical engineering of AC/DC hybrid distribution network.2)Based on the proposed quadratic constrained power flow model for AC/DC hybrid distribution network with flexible DC,the distributed generation and energy storage system are uniformly described in the power flow equation.Thus,a three-phase state estimation model for AC/DC hybrid distribution network is proposed.According to the observability of AC/DC hybrid distribution network,the measurement equation are further given to ensure observability requirements.On the AC/DC hybrid distribution network test system,the original dual interior point method is used to solve the problem.Finally,The validity and practicability of the method are verified by estimation error,iteration time and iteration number.3)In order to solve the problem of inaccurate description or inconvenient solution on the power flow constraint in optimization scheduling for AC/DC hybrid distribution network,the second-order cone relaxation is used to convert power flow constraint into a second-order cone type.Based on second-order cone programming,an AC/DC hybrid distribution network day-to-day optimization scheduling model realizes the active-reactive joint optimization scheduling of AC/DC hybrid distribution network,with the sum of purchase cost,network loss cost and penalty cost of abandonment as the objective function,through dynamic reconstruction and multiple active management.The results of the cases show the effectiveness of the proposed model.