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Impact of variable renewable energy sources on the power system frequency stability and system inertia

202431 citationsOpen accessDedan Kimathi University of Technology

In plain language

Increasing variable renewable energy sources reduces traditional power system inertia, which can undermine grid frequency stability and transient dynamics. Simulating an IEEE 14-bus network using Siemens PTI PSS/E software, the research examines both frequency response and synchronous machine rotor angle behaviour. Although renewable energy can assist system stabilisation within certain boundaries, higher penetration creates more oscillatory and less coherent machine movements. A critical penetration limit of roughly 44 percent was identified. Beyond this level, the network encounters faster rates of change of frequency, deeper frequency nadirs, longer recovery periods, and a higher risk of triggering protective mechanisms such as under-frequency load shedding. To counter these vulnerabilities, the deployment of virtual inertia is highlighted, pointing to solutions like fast frequency response, battery storage systems, and supercapacitors to sustain grid security.

Key takeaways

  • Integrating variable renewable energy reduces system inertia, leading to degraded frequency response and heightened instability risks.
  • A critical renewable penetration threshold of approximately 44 percent was identified, beyond which network stability risks escalate sharply.
  • Exceeding the penetration threshold causes faster rates of change of frequency, lower frequency nadirs, and higher risks of protection relay activations.
  • While renewable energy can aid stabilisation within permissible limits, it introduces more oscillatory and less coherent machine behaviour.
  • Virtual inertia technologies, including battery energy storage and supercapacitors, are proposed to compensate for lost conventional generator inertia.

Why it matters

Transitioning to clean power requires adding large volumes of renewable energy to electricity grids. However, replacing traditional power plants reduces grid inertia, making electricity networks vulnerable to rapid frequency drops and blackouts. Identifying operational thresholds, such as the 44 percent limit, helps operators balance decarbonisation goals with the technical measures needed to keep national power supplies stable and reliable.

Commercialisation angle

Grid operators, utilities, and energy regulators can use these findings to inform grid codes, planning models, and renewable integration limits. The research also supports equipment vendors developing virtual inertia, battery energy storage systems, and supercapacitors for fast frequency response. Tested through software simulations on a standard test network, this is early-stage research that provides analytical frameworks and operating boundaries rather than a finished commercial product.

AI-generated from the published abstract. Always read the original work before citing.

Abstract

Achieving net-zero emissions in line with the Paris Accord necessitates significantly increasing VRES deployment. This study investigates the impact of VRES integration on power system transient stability, extending beyond frequency response to examine synchronous machine rotor angles and system inertia. A novel contribution of this study lies in its systematic exploration of the nonlinear dynamics of power systems, comprehensively investigating the impact of VRES integration on power system stability, focusing on frequency response and rotor angle dynamics. As inertia declines due to VRES integration findings reveal a concerning trend of deteriorating frequency response. This trend suggests a likelihood of frequency instability at high VRES penetration levels, which could trigger the activation of grid protection relay mechanisms. When integrated within permissible limits, VRES can enhance system stabilization, however, this study reveals a trade-off: while VRES integration improves frequency response, it introduces less coherent and more oscillatory machine behavior, underscoring a limit on VRES penetration for maintaining stability. A critical VRES penetration threshold of approximately 44 % was identified, beyond which the system faces heightened risks of instability. Exceeding this threshold introduces significant challenges, including faster RoCoF, lower frequency nadirs, extended response times, and an elevated risk of protection relay activations, such as UFLS and RoCoF mechanisms. It is imperative to manage VRES integration to prevent instability carefully. To address this, "virtual inertia" is proposed to compensate for the diminishing inertial response of traditional generators. Techniques such as FFR, battery energy storage systems, and supercapacitors are recommended for further research and integration. This holistic approach is essential for maximizing VRES penetration while ensuring grid stability. The insights gained from this study can inform policy decisions, grid planning, and the development of control strategies to optimize VRES integration while ensuring grid stability and compliance with grid codes. This study has been implemented on an IEEE14 bus system using Siemens PTI PSS/E software.

Research topics

  • Power System Optimization and Stability
  • Frequency Control in Power Systems
  • Microgrid Control and Optimization

Sustainable Development Goals

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DOI: 10.1016/j.egyr.2024.10.057

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