Research On Optimal Operation Method Of AC/DC Distribution Network

The rapid development of DC distribution network is promoted by the access of numerous flexible DC load and the advancement of power electronics.AC/DC hybrid distribution network becomes the development trend of future smart distribution grid.Optimal operation technology is one of the key technologies to ensure the safe and stable operation of AC/DC distribution network.The optimal operation method of AC/DC distribution network is the focus of this paper.The specific research work is as follows:(1)Aimed at the optimal scheduling problem of multi-microgrid access to AC/DC distribution network,a scheduling method based on different time scales is proposed in this paper.The combination of daily dispatching and rolling optimization method is adopted by the microgrid concentrated controllers in order to achieve continuous and safe operation of the microgrid in normal or abnormal operating states.A real-time dispatching method is adopted by the modular multilevel converter(MMC)concentrated controller in order to realize real-time control of AC/DC distribution network power flow.(2)Aimed at the optimal scheduling problem of AC/DC distribution network with flexible substations,a coordinated optimal scheduling method taking congestion management into consideration is proposed in this paper,considering that the DC distribution system and the AC distribution network belong to different subjects.A coordinated dispatching model for AC/DC distribution network based on distribution locational marginal price(DLMP)is established.The purpose is to adjust the controllable resource scheduling plan of the DC distribution system by market means,optimize the power flow of the DC distribution network,solve the congestion problem of the AC distribution network and realize the friendly interaction between the AC distribution network and the DC distribution network.(3)Aimed at the optimal scheduling problem of AC/DC distribution network with flexible substations,based on the analysis target cascading(ATC),a distributed optimization scheduling method is proposed considering that the DC distribution system and the AC distribution network belong to the same subject.A distributed optimal dispatching model for AC/DC distribution networks with flexible substations is established in this paper.Coordinated optimization between subsystems is achieved by controlling local and coupled variables.Because the communication of the centralized optimization is expensive and the dispatching of the centralized optimization is difficulty,a distributed optimization method is adopted to achieve the overall optimal operation of the AC/DC distribution network under the condition of satisfying operation constraints of the AC/DC distribution network in this paper.