Bottleneck Generator Identification and the Corresponding N-1 Frequency Security Constrained Intraday Generator Dispatch

Abstract

Generators are typically dispatched in a preventive way to guarantee frequency stability in any single generator trip contingency. The largest generator outage is regarded as the severest by the conventional N-1 frequency security rule, since the contingency size is often the dominating factor in traditional systems. However, with the continuous integration of renewable energy sources and fast response devices (e.g., battery), the inertia and frequency response characteristics of generators become diversified. In such situations, the largest generator cannot be simply identified as the bottleneck generator for preventive dispatch, since the post-contingency frequency dynamic is determined by both the contingency size and the frequency response ability of the remaining system. In this paper, a system's frequency response ability (FRA) is quantitatively defined and derived as a function of system intrinsic parameters (e.g., system inertia, ramp rates of generators, load frequency relief coefficient, etc.). Then, the bottleneck generator can be identified through comparing the capacity of a unit with the maximum FRA of its corresponding remaining system. On this basis, an innovative N-1 frequency security constrained optimal intraday generator dispatch scheme is correspondingly established. Simulation results verify the superiority of the proposed method in both frequency security improvement and operation cost saving.