MITSUBISHI ELECTRIC RESEARCH LABORATORIES http://www.merl.com Decoupled Three-Phase Load Flow Method for Unbalanced Distribution Systems Sun, H.; Dubey, A.; Nikovski, D.; Ohno, T.; Takano, T.; Kojima, Y. TR2012-086 October 2012 Abstract This paper proposes a decoupled three-phase load flow analysis method for unbalanced distribu- tion systems. The power flows are solved through nodal current injection mismatch equations written in rectangular coordinates. The voltage changes resulting from nodal current injection mismatches and nodal admittance matrix have been decoupled into one contribution from the real part, conductance matrix, and the other contribution from the imaginary part, susceptance matrix. The method determines voltage changes resulting from conductance and susceptance matrices respectively, and determines the voltages of a node as a linear combination of those voltage changes. The relative contributions are determined based on the diagonals of the con- ductance and susceptance matrices. The constant active power and voltage magnitude(PV) nodes have been converted into constant active and reactive power(PQ) ones based on a sensitivity ma- trix determined through Kron reduction of the nodal admittance matrix, and the corresponding reactive powers are adjusted after each solution has converged. The zero- impedance branches are merged with adjacent impedance branches, and the three phases of a balanced-voltage PV bus are merged into one single- phase PV bus to be modeled in the nodal admittance matrix. Numerical examples on IEEE 37 node test feeder and IEEE 123 node test feeder are presented to demonstrate the effectiveness of the proposed method. IEEE International Conference on Power System Technology (POWERCON) This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc.; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories, Inc. All rights reserved. Copyright c  Mitsubishi Electric Research Laboratories, Inc., 2012 201 Broadway, Cambridge, Massachusetts 02139