Abstract
The utilization levels of the transmission network can be enhanced by the use of automated protection schemes that rapidly respond to disturbances. However, such corrective systems may suffer from malfunctions that have the potential to exacerbate the impact of the disturbance. This paper addresses the challenge of jointly optimizing the dispatch of generators and protection settings in this context. This requires a holistic assessment of the cyber (protection logic) and physical (network) systems, considering the failures in each part and their interplay. Special protection schemes are used as a prototypical example of such a system. An iterative optimization method is proposed that relies on power system response simulations in order to perform detailed impact assessments and compare candidate solutions. The candidate solutions are generated on the basis of a security-constrained dispatch that also secures the system against a set of cyber failure modes. A case study is developed for a generation rejection scheme on the IEEE reliability test system (RTS): candidate solutions are produced based on a mixed integer linear programming optimisation model, and loss-of-load costs are computed using a basic cascading outage algorithm. It is shown that the partial security approach is able to identify solutions that provide a good balance of operational costs and loss-of-load risks, both in a fixed dispatch and variable dispatch context.
Highlights
The electricity grid is primarily recognized as a physical transport layer for electrical energy
We consider a restricted set of decisions where the dispatch D has been fixed, and the operator only determines the optimal SPS settings S: Because the set of possible SPS settings is finite, it becomes possible to enumerate all SPS configurations and their corresponding outcomes, despite the need to invoke a simulator for each operating point
The dispatch is determined through an optimal power flow (OPF) that is secured against the contingencies in set Cn; but not against those in the SPS-triggering contingencies Cp
Summary
The electricity grid is primarily recognized as a physical transport layer for electrical energy. The principle is simple: SPSs take corrective actions upon the occurrence of a network contingency to avoid overloading the remaining circuits In this second application, SPS helps to reduce generation dispatch costs, for example when large amounts of remote renewable resources are connected to the grid: preventive security constraints may require costly curtailments of renewable generation and dispatching generators out of merit [7]. The main challenge in this exercise is that the outcomes from SPS malfunctions are often highly nonlinear, for example when the malfunction triggers a cascading outage When it has been attempted at all, a joint cost-benefit analysis of dispatch and protection settings has typically relied on simplified representation of SPS malfunction and the resulting system response, e.g.
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