Majority of distribution networks is unbalanced due to unbalanced loads, asymmetry in transmission lines and two and single phase shunts. These characteristics of distribution systems results in deficiency of convenient methods in analysis of such cases. In this paper, we propose a successful method for solution of the four wire power flow problem. The method is based on the current injection technique and the Newton-Raphson formulation which has better numerical stability and convergence speed comparing with conventional methods. Furthermore, it is capable deal with the distributed generations as PV buses. It can also solve the sub-transmission loops as a part of solution of distribution system. Then, we suggest a modification to the proposed algorithm which drastically improves the convergence speed by reducing the number of the iterations and computational cost of each iteration. The method is applied to several cases and the results are presented.

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