Introduction

Network topology plays a pivotal role in the reliability and resilience of power systems, especially when integrating renewable energy sources like photovoltaics (PV) and energy storage systems. In the context of renewable energy, resilience refers to a system's ability to maintain service during adverse conditions, while reliability refers to its capacity to consistently meet demand under normal conditions (International Energy Agency [IEA], 2020). Different network topologies, such as Radial, Ring, and Meshed, each exhibit varying levels of resilience to disturbances like grid outages, which are critical for renewable energy systems that rely on intermittent generation and storage. This report explores the influence of network topology on renewable energy systems' resilience and reliability, utilizing a case study that simulates the performance of different network topologies during a grid outage.

Network Topologies and Their Impact on Reliability and Resilience

Network topologies in electrical grids can be classified into several types: Radial, Ring, and Meshed. Each topology offers distinct advantages and challenges in the context of renewable energy integration. Radial networks, characterized by a single path for electricity flow, are the simplest but less resilient in the event of faults or outages. Ring networks, which allow for electricity to flow in multiple directions, provide higher reliability and resilience, as they can redirect power flow in case of failure. Meshed networks, with multiple interconnected paths, offer the highest level of redundancy and are most resilient to disturbances, such as faults or outages.

In the integration of renewable energy, the reliability of power systems depends not only on the ability to generate energy but also on the network's capacity to deliver that energy to the end users in a stable manner (AEMO 2018) (AEMO 2022). The resilience of renewable energy systems is particularly important during periods of intermittency (e.g., cloud cover or low wind) or unexpected grid outages. Efficiently managing renewable energy resources, such as PV and battery storage systems, during such events is essential for grid stability (AEMO 2023).

Case Study: Network Topology during a Grid Outage

This case study is an original and illustrative simulation, developed for research and conceptual analysis using synthetic data and modelled scenarios to represent realistic power network topologies. It simulates the behaviour of three different network topologies—Radial, Ring, and Meshed—during a grid outage. In Figure 1, A 24-hour load profile and PV generation profile are assumed, with a community battery system that starts with a 5 MWh capacity. The grid outage is modelled to occur between hours 14 and 18. Each topology has different efficiencies during the outage: Radial (60%), Ring (85%), and Meshed (98%). The community battery system can discharge up to 2 MW per hour, and its state of charge (SOC) is tracked throughout the simulation.

The results demonstrate that, under normal conditions (hours 0–13 and 19–24), all topologies meet the full load demand. However, during the outage, the performance of each topology varies. The Radial topology performs the worst, serving only 60% of the load during the outage. This topology's lower efficiency and lack of redundancy lead to a higher reliance on battery storage, which depletes more rapidly compared to the other topologies. The Ring topology, with moderate redundancy, performs better, serving 85% of the load during the outage. The Meshed topology, benefiting from the highest level of redundancy and connectivity, manages to serve nearly all of the load, even during the outage, with minimal reliance on battery storage.

Figure 2 tracks the SOC of the community battery. The results show that the Radial network depletes the battery storage the fastest, followed by the Ring network, while the Meshed network exhibits the least battery depletion. This further underscores the impact of topology on renewable energy reliability and resilience. The ability of the Meshed network to maintain a higher level of service during the outage suggests that systems with greater redundancy and interconnectivity are better equipped to handle disturbances, minimizing the impact on both power delivery and energy storage systems.

Discussion

The results of this case study clearly illustrate the importance of network topology in ensuring the reliability and resilience of renewable energy systems, especially in the face of grid disturbances. While the Radial network's simplicity makes it cost-effective and easy to deploy, it is not well-suited for scenarios involving renewable energy sources, which are often intermittent. The Ring topology provides moderate resilience, with better ability to redirect power during disturbances, but still relies heavily on storage systems during outages. The Meshed topology, offering the most redundancy, ensures a more stable and resilient system by providing multiple pathways for energy distribution, reducing the reliance on battery storage during outages, and improving the overall reliability of renewable energy systems.

The case study also highlights the critical role of energy storage systems in maintaining resilience. Batteries can be used as an essential resource during grid outages, but their effectiveness depends on the network’s ability to efficiently distribute power. A more resilient network topology (like Meshed) reduces the stress on energy storage, prolonging its use and ensuring continuity of power supply.

Conclusion

The role of network topology in renewable energy reliability and resilience cannot be overstated. As renewable energy systems become more integrated into the grid, the need for robust, resilient, and flexible network topologies becomes paramount. The case study demonstrates that Meshed networks, with their higher interconnectivity, offer the best performance in terms of both reliability and resilience during grid outages, while Radial networks are the least effective in such scenarios. Future research should focus on optimizing network design and exploring hybrid topologies to balance cost, performance, and resilience in renewable energy integration.

References

International Energy Agency (IEA) (2020). Empowering electricity resilience. International Energy Agency.  https://www.iea.org/reports/empowering-electricity-resilience

Australian Energy Market Operator (AEMO) (2018). Engineering framework. https://aemo.com.au/en/initiatives/major-programs/engineering-framework

Australian Energy Market Operator (AEMO) (2022). Integrated System Plan (ISP).

https://aemo.com.au/energy-systems/major publications / integrated-system-plan-isp

Australian Energy Market Operator (AEMO) (2023). Engineering Framework: Operational Resilience, AEMO | Engineering Roadmaps.