Power Grid Stability Issues
Power grids are critical infrastructure in modern society, and their stability has long been ensured by established methods. However, the landscape is changing rapidly due to a global shift towards sustainable energy. This transformation, driven by environmental concerns, introduces both increased variability and uncertainty. The rising influence of renewable energy and power electronics presents new challenges in managing grid stability. As renewable energy becomes a larger part of our energy mix, the task of ensuring reliability becomes more complex.
Join me as we explore what makes a grid stable, the challenges, and promising solutions in the sections ahead! Let’s dive into the heartbeat of our power systems together! 🔍⚡🌐
Grid Stability Pillars
According to the main system variable in which the instability event is observed, power system stability is generally classified into rotor angle stability, voltage stability, and frequency stability [1]. Power system stability is defined as the ability of an electrical power system to maintain stable operation after being subjected to large fault events. There are three types of stability associated with the power system: rotor angle stability, voltage stability, and frequency stability. All three must be met all the time to maintain the security of the network [2]. In this research, inertia stability is also included considering its fundamental role in supporting both frequency and voltage stability. Additionally, a focus will be placed on the converted-driven stability factor concerning future power systems.
Frequency stability
Frequency stability refers to the ability of a power system to maintain a steady frequency following a severe system upset that results in a significant imbalance between generation and load. Instability occurs in the form of sustained frequency swings that lead to tripping of generating units and/or loads [1]. Even small frequency variations of 0.5% can damage equipment and infrastructure. If the situation is not corrected, load dropping and blackouts can occur. Over-frequency can cause the equipment and infrastructure to overheat or burn while under-frequency can decrease their performance.
Frequency stability has both short- and long-term issues. The time frame of interest spans from several seconds to several minutes, depending on the nature of the different controllers that kick in after the occurrence of a power imbalance [1].
Voltage Stability
Voltage stability refers to the ability of a power system to maintain steady voltages close to their nominal values at all buses in the system after being subjected to a disturbance. It is largely a load-oriented issue and depends mainly on the ability to maintain or restore equilibrium between the load demand and the power supply that is transferred from generators via the network [1]. If the voltage is too high, the equipment will run too fast, which will shorten its useful life. If the voltage is too low, it may result in poor electrical equipment performance, such as dimming or blinking light bulbs.
Voltage stability has both short- and long-term issues that involve fast- and slow-acting load components, respectively. The time frame of interest varies from a few seconds to tens of minutes [1].
Rotor Angle stability
Rotor angle stability, or simply angle stability, refers to the ability of synchronous generators (SGs) and motors in a power system to remain in synchronism after being subjected to a disturbance. Angle stability is usually seen as a generator-oriented issue and depends on whether each SG in the system can maintain or restore its equilibrium between electromagnetic torque and mechanical torque. Instability occurs in the form of increasing angular swings of some generators, leading to their loss of synchronism with other generators. Angle stability is a purely short-term problem, as the time frame of interest is several seconds [1].
Inertia
The stability of traditional power systems depends mainly on the rotating masses of the synchronous thermal generator rotor coupled with the grid. This is known as system inertia. It is a measure of the degree of power system stability to ride through disturbances and maintain voltage and frequency stability [3]. Inertia is an inherent property of the power system that resists change in speed and its value depends on the number of online synchronous generators. When a fault occurs in the system, inertia slows down the rate of change of frequency (RoCoF). It buys time for governor-equipped synchronous generators to operate and arrest frequency changes in the early stages of a disturbance [2].
Converter-driven stability
Future grids will increasingly rely on renewable generation based on converter-interfaced generators (CIGs), which have significantly different features. The CIGs may cause instability phenomena over a wide spectrum, which can be classified into fast- and slow-interaction issues. Since CIG modeling involving electromagnetics is an emerging field, standard models have not yet been developed [1].
Stability Issues and Potential Solutions
Navigating the landscape of power grid stability, we encounter the primary challenge — the integration of renewables, particularly inverter-connected devices, alongside the simultaneous decommission of synchronous rotating generators[3]. The inclusion of renewables amplifies the intricacies of power system stability, influencing power flow patterns, reactive power sufficiency, and system inertia. As we delve into the nuances of incorporating renewable sources into the energy mix, a cascade of consequences unfolds as well as innovative solutions impacting the stability of the system [4].
The lack of inertia
Diminishing system inertia, especially with the integration of renewable sources, amplifies the risk of deeper frequency excursions and higher rates of change of frequency (RoCoF), compromising the stability and performance of the power grid.
Power grid flexibility
A key challenge is the intermittency and variability of renewable generation due to their weather dependency, which has prompted questions regarding the reliability and flexibility of a power network [2].
Voltage disruption
Grid voltage instability can lead to fluctuations that disrupt the smooth flow of electricity. Sudden voltage changes pose a risk to the reliability and functionality of electrical equipment.
Frequency disturbances
Power grid frequency instability issues can compromise the synchronization of interconnected systems, potentially causing equipment malfunctions.
Recap
In our exploration of power grid stability, we learned about the intricacies of frequency, voltage, rotor angle, inertia, and converter-driven stability. Unveiling the challenges within these elements, we uncovered the critical issues plaguing our grids — lack of inertia, power flexibility woes, voltage disruptions, and frequency disturbances. The path to a robust and resilient power system became clear as we delved into innovative solutions to counter these challenges.
As we wrap up, it’s evident that the hurdles are real, but so are the solutions. From tackling the inertia dilemma to addressing power flexibility, we’ve explored groundbreaking strategies to improve our grids. The future of power stability is bright, and it’s driven by innovation.
I invite you to continue this journey. Stay tuned to the next blog post on the latest developments in power markets, batteries, and other energy solutions, also follow me on Medium if you think this post was helpful. Let’s continue this conversation, explore new horizons, and empower ourselves with the knowledge! 👏🏻👏🏻
References
- Tao Liu, Yue Song, Lipeng Zhu, David J. Hill, Stability and Control of Power Grids, Annual Review of Control, Robotics, and Autonomous Systems 2022 5:1, 689–716, https://doi.org/10.1146/annurev-control-042820-011148
- Faraedoon Ahmed, Dlzar Al Kez, Seán McLoone, Robert James Best, Ché Cameron, Aoife Foley, Dynamic grid stability in low carbon power systems with minimum inertia, Renewable Energy, Volume 210, 2023, Pages 486–506, ISSN 0960–1481, https://doi.org/10.1016/j.renene.2023.03.082.
- Dlzar Al kez, Aoife M. Foley, Neil McIlwaine, D. John Morrow, Barry P. Hayes, M. Alparslan Zehir, Laura Mehigan, Behnaz Papari, Chris S. Edrington, Mesut Baran, A critical evaluation of grid stability and codes, energy storage and smart loads in power systems with wind generation, Energy, Volume 205, 2020, 117671, ISSN 0360–5442, https://doi.org/10.1016/j.energy.2020.117671.
- Giovanni Sansavini, Paolo Gabrielli, Blazhe Gjorgiev, Behnam Akbari, Linda Brodnicke, Kate Lonergan, Raphael Wu, Thomas Kocher, Jan Berger, Werner Collenberg, Changing energy mix and its impact on grid stability, Swiss Re, 2021. Available online at https://corporatesolutions.swissre.com/insights/knowledge/changing-energy-mix-and-its-impact-on-grid-stability.html
