On quantification of flexibility in power systems

Abstract

Abstract-Large scale integration of fluctuating and nondispatchable generation and variable transmission patterns induce high uncertainty in power system operation. In turn, transmission system operators (TSOs) need explicit information about available flexibility to maintain a desired reliability level at a reasonable cost. In this paper, locational flexibility is defined and a unified framework to compare it against forecast uncertainty is introduced. Both metrics are expressed in terms of ramping rate, power and energy and consider the network constraints. This framework is integrated into the operational practice of the TSO using a robust reserve procurement strategy which guarantees optimal system response in the worst-case realization of the uncertainty. An illustrative three-node system is used to investigate the procurement method. Finally, the locational flexibility for a larger test system is presented.

Flexibility and Resiliency of Electric Power Systems: Analysis of Definitions and Content

“…Operational flexibility is the capability of the EPS to absorb disturbances for maintaining a secure operating state. Locational flexibility is the operational flexibility at the given bus in the grid [2].…”

Effect of Energy Storages on Flexibility and Cyber Resilience of Electric Networks

“…A model of a node with ESs that can be used for quantifying the EPS flexibility is proposed in Ref. [14,15]. Dynamic behavior of some node i with ESs can be approximately represented by a differential discrete in time first-order equation:…”

“…Methodology of flexibility quantification for individual nodes of RES with ES and the network as a whole is proposed in [15]. For the purpose of quantification they introduce two notions: 1) Functional (operational) flexibility is ability of an energy system to absorb disturbances to be able to maintain steady-state operability; and 2) Territorial (localized) flexibility is functional flexibility available in a specific node of the network.…”

Quantification of Intra-hour Security-Constrained Flexibility Region

“…The availability of operational flexibility can be studied via the existence of feasible operation strategies. In [5] and [26], operational flexibility is the ability of the power system to react to a disturbance to keep the system secure. The available flexibility, considering the ramping, capacity, and energy of dispatchable generators, transmission constraints in DC power flow, and N-1 reliability criterion, is described as a polyhedron entitled "flexibility set", or "reach set" in [27].…”

“…where ρ is a vector of a sufficiently large number (e.g., 1E4) with the compatible size. If ρ T (s 1 + s 2 ) → 0 by solving (26), a worst-case realization ofd, which leads to a feasible SP in (20), is generated. Otherwise, a worst-case realization ofd leading to an infeasible SP in (20) is identified.…”