Co-Simulation Of Transmission And Distribution Networks

With the development of smart grid, an increasing scale of distributed energy resources (DERs) are integrated into distribution networks. DERs may change the traditional single-direction power flow characteristic of distribution networks, and therefore challenge the simulation of transmission-distribution interconnected systems, which is vital to power system analysis and control. In this thesis, a decomposition-coordination algorithm is proposed for the co-simulation of the interconnected network, and a platform is established based on PSASP and DIgSILENT/PowerFactory.This thesis proposes a hybrid modeling method for the interconnected system, and uses phase model and sequence model for the transmission and distribution system, respectively. In power flow calculations, traditional algorithms like Newton-Ralfson method and back/forward sweep method are used for the two systems, respectively. After convergence, decomposition-coordination equations based on system boundary power are solved to obtain the overall power flow results of the interconnected system. Accuracy and convergence of the proposed algorithm are verified by standard IEEE systems.Based on the proposed power flow algorithm, a simulation platform is established. In the platform, PSASP and DIgSILENT/PowerFactory are used as power flow calculators for transmission and distribution systems, respectively, and MATLAB is used as a coordinator. Communication interfaces between calculators and the coordinator are designed.