Power Flow Model Selection Method of Distribution Network Analysis and Optimization

DC power flow can greatly simplify the modeling of distribution network analysis and optimization. However, there is a lack of theoretical analysis and quantitative basis for what conditions DC power flow model can be adopted. For this reason, this paper proposes a method to select the power flow model according to the length of the feeder. Firstly, distribution system dispatchable region (DSDR) based on AC power flow model is established, capacity boundary and voltage boundary are defined as well. Secondly, the position relationship between capacity boundary and voltage boundary with different length of feeders is studied. The dividing point between capacity constraint and voltage constraint is found, that is, the critical length of feeders. Thirdly, power flow model selection method based on the critical length of the feeder is proposed. If the length of feeder is less than the critical length, the capacity constraint is stricter. As long as the capacity constraint is satisfied, the voltage constraint must be satisfied. This means that the voltage constraint can be ignored and the DC power flow model can be adopted. On the contrary, the AC power flow model should be adopted. In addition, this paper also discusses the influence of wire parameters, power factor, voltage regulation measures and other factors on the critical length. Finally, the IEEE 33 buses case is given to verify the correctness of the proposed method and conclusion.