Accuracy Enhancement of Mixed Power Flow Analysis Using a Modified DC Model

The mixed power flow analysis method decreases the computational complexity and achieves a high level of simulation accuracy. The mixed approach combines the ac with the dc power flow models, depending on the area of interest. The accurate ac model is used in the study area of interest to obtain high simulation accuracy, while the approximate dc model is used in the remainder of the system to reduce the required computations. In the original mixed approach, the errors originating from the use of the dc model may propagate to the area of interest where accurate simulation outcomes are required; thus, the simulation accuracy might not be satisfactory. This paper presents a new method of enhancing the simulation accuracy of the mixed power flow analysis using available information. In the proposed approach, a modified dc model is used instead of the traditional one and is constructed from an initial base-case ac solution. The new dc model compensates for the errors originating from the neglect of the real power losses and the assumption of a flat voltage magnitude in the conventional dc model. Thus, the proposed method can improve the simulation accuracy in the area of interest. The superior computational benefits can also be preserved by maintaining linear characteristics of the dc model. Case studies with the IEEE 118-bus system are provided to validate the enhanced accuracy of the proposed method.