An Improved Forward-Backward Sweep Technique for the Load Flow Analysis of a Distribution Network with Accurate Modeling of Zero Sequence Voltages

摘要

The objective of this paper is to improve the accuracy of the results obtained from the load flow analysis of a distribution network via forward-backward sweeps. Specific attention is paid to the two-port modeling of a transformer with precise consideration for the zero sequence components of its port voltages. The zero sequence voltages at transformer ports are often ignored in the conventional load flow analyses. A new two-port network model is derived, which is generalized enough for the accurate representation of a transformer in the cascaded connection. Based upon the novel two-port representation made, a new set of iteration rules is established to carry out the forward-backward sweeps for solving the load flow results. All possible transformer configurations are taken into account. It is shown that the load flow analysis technique proposed is suitable for both active and passive distribution networks. The accuracy analysis of the load flow results is also carried out. For a given load flow result, by assessing the nodal current imbalances are evaluated based upon the admittance matrix representation of the network. Case study is performed to demonstrate the utility of the proposed load flow analysis technique.