Abstract
The post-contingency loadability limit (PCLL) and the secure operating limit (SOL) are the two main approaches used when computing the security margins of an electric power system. While the SOL is significantly more computationally demanding than the PCLL, it can account for the dynamic response after a disturbance and generally provides a better measure of the security margin. In this study, the difference between these two methods is compared and analyzed for a range of different contingency and load model scenarios. A methodology to allow a fair comparison between the two security margins is developed and tested on a modified version of the Nordic32 test system. The study shows that the SOL can differ significantly from the PCLL, especially when the system has a high penetration of loads with constant power characteristics or a large share of induction motor loads with fast load restoration. The difference between the methods is also tested for different contingencies, where longer fault clearing times are shown to significantly increase the difference between the two margins.
Highlights
Electric power systems are generally operated according to the N − 1 contingency criterion, meaning that the system should be able to with stand the loss of any single system component, such as a transmission line or a generating unit, without losing stability
While this study focused on the impact of different load models, converter-interfaced generation and other power electronic devices in the power system will have a significant impact on the computed security margins
A meth odology was developed to allow a fair comparison between the two methods to ensure that the difference in the computed security margins was due to actual differences of the security margin approaches, and not caused by differences in the simulation setups
Summary
Electric power systems are generally operated according to the N − 1 contingency criterion, meaning that the system should be able to with stand the loss of any single system component, such as a transmission line or a generating unit, without losing stability. Two main approaches are used to compute the security margins of a power system: the post-contingency loadability limit (PCLL) and the secure operating limit (SOL) [1,2]. The PCLL is evaluated by estimating the loadability limit of a post-contingency operating point, where a so lution path is traced by iteratively increasing the system stress until the system’s critical point is reached. An alternative measure of the security margin is the SOL, which refers to the most stressed pre-contingency operating state in which the system can withstand a specified set of contingencies. The SOL requires numerous full time-domain or quasi steady-state (QSS) simulations to trace the security limit for a set of different contingencies, a task that is generally too time-consuming to meet the near real-time monitoring requirements of system operators
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
