Abstract
This paper proposes a novel energy based technique called the Robustness Area (RA) technique that measures power system robustness levels, as a helper for planning Power System Restorations (PSRs). The motivation is on account of the latest blackouts in Brazil, where the local Independent System Operator (ISO) encountered difficulties related to circuit disconnections during the restoration. The technique identifies vulnerable and robust buses, pointing out system areas that should be firstly reinforced during PSR, in order to enhance system stability. A Brazilian power system restoration area is used to compare the guidelines adopted by the ISO with a more suitable new plan indicated by the RA tool. Active power and reactive power load margin and standing phase angle show the method efficiency as a result of a well balanced system configuration, enhancing the restoration performance. Time domain simulations for loop closures and severe events also show the positive impact that the proposed tool brings to PSRs.
Highlights
Power systems are developed to perform with high reliability, even though, critical outages may trigger a cascade of events ending up in a blackout
J =1 where: n is the number of system buses; Pi and Qi are, respectively, the specified active and reactive power injections of the ith bus; Vi is the voltage magnitude and θi, the respective phase angle; Bij refers to the transfer susceptance between buses i and j, and Gij is related to the transfer conductance; θij is the angular difference between buses i and j
The event considered is a full load shedding at bus 561, which is a severe event and is likely to occur to recently connected loads during Power System Restoration (PSR) due to inappropriate protective actions during grid instabilities [11]—for instance: voltage sags or sudden load variations
Summary
Power systems are developed to perform with high reliability, even though, critical outages may trigger a cascade of events ending up in a blackout. The Power System Restoration (PSR) in Brazil is based on hydro Generator Units (GUs) [3], providing a short black start period with renewable energy sources It is, a continental sized power system with long high voltage transmission lines connecting 1076 power plants. Planning PSRs requires expertise to deal with limitations and constraints, where poor voltage profile and frequency control problems are recurrent [12,13,14] Such issues are mainly caused by thermal limitations on GUs and transmission lines stability contrains.
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