Benefits of coordination of flexible devices and probabilistic security standard in transmission network operation

Abstract

Currently, transmission network security is treated within a deterministic and preventive control framework where network constraints and balancing costs are not fully optimised. This may be inefficient and lead to increased levels of congestion, potentially increasing cost of integration associated with low-carbon generation. In this context, this thesis assesses the effects of coordinating FACTS and HVDC transmission systems under both deterministic and probabilistic security frameworks and assuming an array of available preventive/corrective control actions. An deterministic/probabilistic cost-benefit model has been developed for assessing the economic and reliability performance of alternative control strategies enabled by coordination of flexible devices. Results demonstrate that probabilistic security for flexible AC/DC devices coordination is significantly more beneficial since it can lead to lower operating costs, increased infrastructure utilisation and improved reserve allocation across GB network. The framework is further developed to explicitly consider the likelihood of post-contingency events and wind uncertainty. A tight MILP representation, two novelty transmission losses penalty items and scenario reduction model are proposed to reduce computational burden in the large-scale system. Results demonstrate the advantages of probabilistic security to improving the overall efficiency of the system when integrate uncertain renewable generation. Adding flexible network technology could even increase system costs under a preventive security approach. Finally, a novel two-stage stochastic optimization model that incorporates effect of dynamic line rating (DLR) on transmission network operation with increased penetration of wind generation is proposed. The stochastic model co-optimizes energy and reserve holding levels for the forecasted/expected condition along with re-dispatch actions under real-time operation. The benefits of using DLR are demonstrated in terms of overall cost minimization, albeit reserve levels may be increased due to DLR uncertainty. Results also demonstrate that reserve services can be shared among multiple uncertainties. The impacts of forecast accuracy and reserve price on the performance of DLR is discussed.