Impacts of Constraint Relaxations on Power System Operational Security

Abstract

Constraint relaxations by definition mean that certain constraints are allowed to be violated in energy market models for a pre-determined penalty price. System operators utilize this mechanism in an effort to impose a price-cap on shadow prices in the markets. In addition, constraint relaxations can serve as corrective approximations that help to reduce the occurrence of infeasible or extreme solutions in market models. This work aims to capture the impact constraint relaxations have on AC operating conditions. Moreover, this analysis also provides a better understanding of the correlation between DC market models and AC systems and analyzes how relaxations in market models propagate to system operations. This information can be used to assess the risk associated with constraint relaxations. The practice of constraint relaxations was replicated in this work using a test case and a real-life large-scale system, while capturing both energy market aspects and AC system performance. System performance investigation included static and dynamic security analysis for base-case and post-contingency conditions. Index Terms-Optimal power flow, power generation dispatch, power system economics, power system security, power system simulation, power system stability.

Revisit power system dispatch: Concepts, models, and solutions

“…Noted that it is nearly impossible to find a feasible solution that meets all the requirements. Hence, it is a common practice to add relaxations for the constraints and set different levels of penalty factors as a punishment for the constraint violations [48,49] . Because of the large value of punishment, the coefficients matrices have a wide range of values, causing practically numerical issues and challenges [50] .…”

Security‐level classification based on power system partitioning

“…The operation risk of power system is considered in [4,5]. Note that these studies in [3][4][5] do not consider the influence of power system structure, then topological structure security of power system is studied in [6]. The security of the power equipment in power system is investigated in [7].…”

“…Traditional security assessment of power systems mainly focuses on one aspect of the operation state or power system structure, and these two factors have not been successfully combined in existing studies. The impact of constraints on power system operational security is studied in [3]. The operation risk of power system is considered in [4,5].…”