The Thevenin equivalent based power flow method for integrated transmission and radial distribution networks

With the large-scale integration of distributed generations into distribution networks (DNs), collaborative analysis for integrated transmission and distribution (T&D) networks is increasingly important. The fast collaborative power flow method with good convergence plays an important role in the real-time security analysis and off-line planning design for the T&D networks. The master-slave-splitting (MSS) method, a representative power flow method for integrated T&D networks, has more iterations and worse convergence when radial distribution networks (RDNs) have heavy loads, which hinders the analysis and decision-making for coordinated transmission and radial distribution (T&RD) networks. Therefore, this paper deduces theoretically the reason for the MSS method performance deterioration under heavy loads conditions in RDNs, and explore the improvement idea firstly. Then based on the improvement idea, the Thevenin equivalent based power flow (TEBPF) method for integrated T&RD networks is proposed. Known from the theoretical analysis, the TEBPF method can guarantee better convergence and less iterations in the heavily loaded RDNs compared with the MSS method. Simulation results demonstrate the effectiveness of the method proposed and the correctness of the deduction.