Voltage stability constrained optimal power flow (VSCOPF) with two sets of variables (TSV) for reactive power planning

The key of reactive power planning (RPP), or Var planning, is the optimal allocation of reactive power sources considering location and size. First, the relationships of Var compensation, total transfer capability (TTC), and fuel cost are introduced in this paper. Second, the enumeration approach for RPP is briefly described. Although time-consuming, it provides a global view of the relationship between the system cost and local Var compensation, which is useful for benchmarking purposes. Third, the voltage stability constrained optimal power flow (VSCOPF) model with two sets of variables (TSV) approach is used to combine a large number of OPFs in the enumeration approach to achieve an efficient model. The two sets of variables correspond to the normal operating point and the collapse point, respectively. The computational complexity of TSV is tremendously reduced. Different from the previous work using Var cost minimization as the objective, this work proposes to use the total system cost (fuel cost and Var cost) minimization as the objective. This leads to significantly different results. The observed results have important implication to RPP, especially under the deregulated environment. That is, it verifies that RPP should consider the impact to system dispatch considering generation cost. The results from the TSV approach are also benchmarked with the enumeration approach. Finally, conclusions are presented.