In the rapidly evolving landscape of renewable energy, microgrids are emerging as a critical component, offering resilience and flexibility in power distribution. However, the increasing integration of grid-forming inverter interfaced distributed energy resources (DERs) into these microgrids presents unique challenges, particularly in protection schemes. Traditional relay protection systems are struggling to keep up with the demands of modern microgrids, which can operate in various modes, including islanded states.
Yubo Yuan, a researcher from State Grid Jiangsu Electric Power Co. Ltd., has published a groundbreaking study in the EAI Endorsed Transactions on Energy Web (formerly known as the International Journal of Energy Web and Information Technology). The research addresses the limitations of conventional protection schemes and proposes a novel on-site protection scheme tailored for microgrids with a high penetration rate of grid-forming DERs.
The study begins by analyzing the fault characteristics of grid-forming DERs and delves into the current, voltage, and phase angle differences between these resources under different microgrid operation modes. Yuan explains, “Traditional protection schemes often lose selectivity, making it difficult to pinpoint and address faults accurately. Our research aims to overcome this challenge by leveraging the phase angle difference between pre-fault voltage and post-fault current to determine fault direction.”
One of the key innovations in Yuan’s research is the development of an internal fault acceleration factor that integrates phase angle difference and measured impedance. This factor enhances the action equation of inverse time overcurrent protection, significantly improving its effectiveness. Additionally, the study introduces a low-voltage protection criterion based on comprehensive phase angle difference characteristics. This criterion addresses the issue of insufficient fault current during two-phase short-circuit faults in islanded states, ensuring that inverse-time overcurrent protection can be triggered.
The proposed protection scheme combines improved inverse-time overcurrent protection with low-voltage protection, offering a robust solution for microgrids. To validate the effectiveness of the scheme, Yuan and his team built a model using PSCAD, a widely-used power system simulation tool. The simulation results, along with theoretical analysis, demonstrate that the scheme operates quickly and reliably in both grid-connected and islanded operation states of the microgrid.
The implications of this research are profound for the energy sector. As microgrids become more prevalent, the need for advanced protection schemes that can handle the complexities of high DER penetration becomes increasingly critical. Yuan’s work provides a blueprint for developing more reliable and efficient protection systems, which can enhance the overall stability and resilience of microgrids.
“This research is a significant step forward in addressing the protection challenges posed by the integration of renewable energy resources into microgrids,” Yuan remarks. “It paves the way for more advanced and adaptive protection schemes that can support the energy transition and ensure a stable power supply.”
The study’s findings are particularly relevant for commercial applications, as they offer a practical solution for protecting microgrids that are increasingly being adopted by industries and communities seeking energy independence and sustainability. By improving the reliability of microgrid protection, this research can accelerate the deployment of renewable energy resources and contribute to a more resilient and sustainable energy future.
As the energy sector continues to evolve, the need for innovative solutions to protect and manage microgrids will only grow. Yuan’s research highlights the importance of ongoing innovation and collaboration in the field, setting the stage for future developments that will shape the energy landscape.