Influence of Load Modeling on the Cost of Ensuring Stability Using TSCOPF

Load modeling significantly impacts the time-domain response of power systems in transient stability studies but this effect is often underestimated in Transient Stability Constrained Optimal Power flow (TSCOPF) studies. The object of this study is twofold: 1) it proposes a robust formulation based on a relevant node representation approach that allows the use of any type of load model in TSCOPF algorithms, while maintaining the accuracy and reducing the size of a full representation approach; and 2) it conducts a comparative analysis of how load modeling influences the cost of ensuring stability and provides a summary of several recommendations for load modeling in these algorithms. The results show that the usual approach in TSCOPF studies, which involves impedance-based load modeling, leads to a significant false stabilization effect in the rotor angle trajectories. On the other hand, the use of the constant power model yields conservative results at a significant computational cost. This paper advocates for the adoption of the relevant node TSCOPF approach proposed in this work, retaining detailed exponential or polynomial load models for their flexibility and accuracy, while incurring only a slight increase in the computational effort.