Effect of dynamic load models on WAC operation and demand-side control under real-time conditions

Abstract

The vast majority of the proposed Wide Area Control (WAC) methodologies is tested and evaluated under the assumption that the system consists only of constant power loads. However, in practice power systems are dominated by non-linear loads, which can potentially affect the smooth operation of the wide area controller and deteriorate the system’s stability. This paper is firstly focused on examining the impact of various and commonly used non-linear load models (static and dynamic), such as the exponential, exponential dynamic, ZIP and ZIP-Induction Motor (ZIP-IM) load models on the WAC performance. Real-time simulations on the IEEE 39-bus dynamic test system indicate that the load recovery dynamics of the exponential dynamic load model have a severe impact on the WAC operation, leading the system to instability. Furthermore, it is illustrated that, loads with constant power/current/impedance characteristics have limited effect on the WAC damping capability, even with dynamics included. To address the impact of the exponential dynamic loads on the WAC performance, a novel wide area controller is proposed for coordinating simultaneously all the synchronous generators and controllable loads of the system. Finally, the effect of the size and flexibility of the controllable demand on the performance of the proposed scheme is also investigated, while the robustness of the proposed scheme is evaluated under measurement errors and erroneous generator parameters.