Transformer branches have been difficult to handle in three phase distribution power flow calculations. A novel method of processing transformer branches is proposed. It can be efficiently introduced into three-phase power flow algorithm for distribution networks. In the proposed method

according to the phase shift relations of the sequence state variables between the two sides of transformers

the phase transformation matrix can be established and the processing of transformer branches can be simplified. Using the structures of three-sequence decoupled distribution networks and the three-sequence decoupling-compensation models of unsymmetrical branches

the sequence path matrices can be generated with the loop analysis method. The relationship between node sequence voltage and injection sequence current can be derived. The three-phase decoupled power flow calculation for unbalanced distribution network containing multi-transformer branches can be realized successfully. Parallel computation can be used for the three-sequence decoupled power flow calculation to achieve higher computational efficiency. Finally

the simulation results of test examples are provided to demonstrate the correctness and effectiveness of the proposed method.