Assessment of PTDF based power system aggregation schemes

Power flow computations are essential for many types of power system analyses. In order to reduce computation time and reflect actual power market operation, network aggregation principles are often used. In this work we discuss network aggregation based on power transfer distribution factors (PTDF), by testing three different aggregation schemes. We analyze the performance of the three schemes comparing their solutions with the results obtained from a DC optimal power flow (DCOPF) performed on the non-aggregated system. The performance is evaluated on the IEEE 30-bus test system using three indicators; power generation, inter-zonal flows, and total system costs. To account for wind and load forecast uncertainty, we consider a modified IEEE 30-bus system proposed to address massive wind integration. The case study results show that the choice of weighting scheme significantly impacts the results. In particular, the PTDF aggregation schemes based on nodal injections (production minus demand) and production outperform the pro-rata aggregation scheme.