Inclusion of Pre-Existing Undervoltage Load Shedding Schemes in AC-QSS Cascading Failure Models

Abstract

A challenging problem facing AC-Quasi-Steady-State (AC-QSS) cascading failure models of power system is the divergence issue primarily stemming from voltage collapse phenomena. In reality, there are undervoltage load shedding (UVLS) relays, which aim to prevent such a collapse by shedding a pre-specified fraction of load at buses where the corresponding voltages fall below a threshold. However, capturing the UVLS action in QSS models is very difficult, because most of the time the model cannot generate an equilibrium below the voltage threshold due to divergence. To address this problem, current models have applied different variants of uniform load shedding (ULS) till convergence is achieved, which differ from the ground truth. In order to solve this, we propose a methodology that leverages the post-ULS load flow as a starting point when divergence occurs. In this condition, a sensitivity index coupled with the voltage magnitudes of buses is used to recognize the buses that are most prone to voltage collapse. The UVLS scheme is then applied to these buses. To verify the accuracy of the results, we also present a suitable dynamic cascade model with appropriate limits and protection details that can selectively capture UVLS action, thereby revealing the proximate ground truth. Predictions of the proposed model are validated against those of the dynamic model for representative cases in IEEE 118-bus system. In addition, results of the proposed model are contrasted with two ULS schemes on the 2, 383-bus Polish system.

An Approach for Fast Cascading Failure Simulation in Dynamic Models of Power Systems

“…In this section, we contrast the cascading failure simulation results in the ground truth (that uses a 4 th -order generator model solved using TM) with the AC-QSS model [29] and dynamic model with classical generator representation. Going forward, 'error' will imply difference w.r.t.…”

Load shedding for frequency and voltage control in the multimachine system using a heuristic knowledge discovery method

“…Recently, researchers are working on load shedding and also on the priority of renewable energy integration in the smart grid. Domestic load shedding is performed in the literature to maintain the supply quality (Azasoo et al, 2020;Alrajhi, 2022), while various sensitivity parameters that combine the negative effects of frequency, voltage, and load shedding are studied through max-min optimization (Alshammari et al, 2018;Alsiraji and El-Shatshat, 2018;Cruz et al, 2020;Talaat et al, 2020;Gharebaghi et al, 2021;Hong and Hsiao, 2022). The authors (Alrajhi, 2018;Jiang et al, 2020) have linearized various components and the system dynamics for load shedding due to the nonlinearity of system voltage dynamics and frequency.…”