Impact of Load Models on Power Flow Optimization
For power system operators and researchers, this highlights that load model choice critically affects optimal power flow solutions, challenging the common use of PQ models.
The paper shows that different aggregated load models (PQ, ZIP) can represent the same power at the optimal solution but lead to vastly different grid operating points. Using CMU campus data, they found that the PQ model accurately characterizes load behavior in only 16.7% of cases.
Aggregated load models, such as PQ and ZIP, are used to represent the approximated load demand at specific buses in grid simulation and optimization problems. In this paper we examine the impact of model choice on the optimal power flow solution and demonstrate that it is possible for different load models to represent the same amount of real and reactive power at the optimal solution yet correspond to completely different grid operating points. We introduce the metric derived from the maximum power transfer theorem to identify the behavior of an aggregated model in the OPF formulation to indicate its possible limitations. A dataset from the Carnegie Mellon campus is used to characterize three types of load models using a time-series machine learning algorithm, from which the optimal power flow results demonstrate that the choice of load model type has a significant impact on the solution set points. For example, our results show that the PQ load accurately characterizes the CMU data behavior correctly for only 16.7% of the cases.