Power Grids Unplugged: How Islanding is Changing Autonomous Energy

Introduction

Islanding refers to a situation in power grids where a part of the grid (i.e., power island) gets separated from the main power network. This can happen intentionally or unintentionally.

Intentional Islanding: This is done for maintenance purposes or to isolate a segment of the grid for safety or operational reasons. It's a controlled process where operators intentionally separate a part of the grid to ensure it can operate independently, typically using local power generation sources.

Unintentional islanding occurs when a part of the grid becomes isolated from the rest due to unexpected events like equipment failures, natural disasters, or faults in transmission lines. In such cases, the event has to be detected, and the generators must be disconnected.

Why islanded operation has been historically prohibited

Traditionally, system operators have prohibited islanded operation due to various concerns, such as:

• Out-of-Phase Reclosing: Islanding was historically prohibited to avoid the risks of reconnecting an islanded section to the main grid without proper synchronisation, which could lead to significant equipment damage due to electrical and mechanical stress.
• Insufficient or Missing Grounding: The ban on islanding helped ensure all parts of the grid were properly grounded, preventing safety hazards like electric shocks and ensuring the stable operation of electrical systems.
• Insufficient Fault Level: Avoiding islanding maintained the necessary fault current levels for properly functioning protective devices, ensuring they could detect and clear faults to prevent system disturbances.
• Changes Needed to Protection & Control Schemes: Historically, islanding was avoided to reduce the need for complex changes in protection and control schemes, which would otherwise increase operational complexity and costs.
• Unacceptable Levels of Voltage and Frequency: Prevent unsuitable voltage and frequency fluctuations, which can harm equipment and reduce the overall performance of the power system.
• Safety Risks for Utility Personnel: Prohibiting islanding has historically been crucial for the safety of utility workers, as it prevents dangerous situations where they might encounter unexpectedly energised lines due to local generation within an islanded section.

As the energy landscape evolves towards greater resilience and flexibility, the traditional prohibitions against islanding in power grids are undergoing significant changes. System operators increasingly recognise the benefits of controlled islanding and microgrids as tools for enhancing grid stability and reliability in the face of diverse challenges, including natural disasters and fluctuations in renewable energy sources.

‍Challenges of Controlled Islanding

Optimising and controlling self-sustained power islands present complex challenges that must be addressed to ensure their safe, reliable, and efficient operation.  

• Limited Visibility: Achieving seamless synchronisation requires real-time visibility on both sides of the Point of Connection (PoC). Limited visibility, especially at the island side of the PoC, creates a blind spot for phase angles, complicating the synchronisation process, particularly if there's a significant electrical distance between measurable voltages and controllable generators within the island.
  
• Stability of Power Island: During synchronisation, grid-forming assets start shifting the equilibrium of the power island towards a new state. This transition can jeopardise stability due to abnormal operating conditions, such as voltage fluctuations, frequency variations, power swings, and overcurrents, potentially leading to the collapse of the power island.
• Non-Homogeneity of Control Characteristics of Grid-Forming Converters: Power islands may include multiple grid-forming converters with varied control characteristics (e.g., different droop settings, gains, etc.) and ratings. This diversity adds control complexity, as converters respond differently to identical control commands, potentially leading to conflicting responses and instabilities.
• Damage to Equipment: Changing system equilibrium can induce transients, like phase jumps and oscillations, leading to abnormal conditions such as overcurrents and overvoltages. These conditions can damage equipment, like transformers, and disrupt system operation.
• Disconnection of Uncontrolled DERs: Power islands may contain a variety of Distributed Energy Resources (DERs), like uncontrolled photovoltaic systems operating in Maximum Power Point Tracking (MPPT) grid-following mode. Abnormal conditions during synchronisation can trigger the disconnection of these DERs, often due to inadequate phase tracking by their Phase-Locked Loops (PLLs).
• Stability of Protective Relays: Protective relays within the power island might react to abnormal conditions and transients—from instantaneous overcurrents to phase jumps—resulting in spurious tripping and unnecessary disconnections, which can further destabilise the island.
• Synchronisation and Stability: Maintaining stability and synchronisation within a self-sustained island remains a fundamental challenge, particularly when it involves maintaining frequency and voltage within safe limits and coordinating with the main grid.
• Protection and Safety: Adapting protection schemes for dual operation modes—connected and islanded—ensures safety but introduces complexity. These schemes must protect personnel and equipment under varying operational scenarios.
• Load and generation Balancing: Balancing supply and demand becomes critical in islanded mode; mismatches can lead to severe frequency and voltage deviations.
• Communication and Control: Robust communication systems are vital for managing transitions between modes and maintaining island performance, posing a challenge in changing environments.
• Regulatory and Technical Standards: Navigating existing regulations and standards while adopting new grid structures adds complexity, as many standards still need to be adapted to the dynamic nature of controlled islanding.
• Grounding Challenges: Ensuring consistent and safe grounding in islanded modes presents significant challenges, impacting fault detection, electrical safety, voltage stability, and the seamless transition between islanded and grid-connected operations.

‍Technologies that support the uptake of self-sustained power islands

The transition towards self-sustained power islands is supported by a suite of innovative technologies designed to address the operational complexities of these systems.

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These technologies are vital for enabling the resilience, stability, and efficiency needed for islanded operations:

• Advanced Grid Management Software: This software acts as the central intelligence of the power island, coordinating various resources, managing power flows, and ensuring high control accuracy of the grid, even under islanded conditions.
• Grid-Forming Converters: These devices are crucial for establishing and maintaining the voltage and frequency of the power island, acting as a virtual synchronous machine to ensure stability and facilitate synchronisation with the main grid.
• Synchrophasors: These precision timing instruments measure the instantaneous voltage, current, and frequency at specific locations on the grid, providing critical data that enables better decision-making for synchronisation and stability.
• Energy Storage Solutions: Energy storage systems, including batteries and other storage technologies, are essential for smoothing out intermittent renewable generation and ensuring reliability within the power island.
• Dynamic Protection Systems: Adaptive protection relays and systems swiftly detect and mitigate faults within the islanded grid, ensuring safety and continuous operation.
• Interoperability Standards and Protocol: To ensure seamless integration and communication between diverse technologies and systems, interoperability standards are established, promoting efficient management and operation.
• Other Smart Grid Technologies: Advanced Metering Infrastructure (AMI) and smart sensors provide the critical data analytics required for real-time load management and responsive control within isolated grids.

By integrating these technologies, power islands can operate more autonomously, providing a reliable and sustainable power supply while offering flexibility to connect with the larger grid infrastructure when beneficial.

Learning from experience: Benefits and countries that support islanded operation.

Islanded operation offers a wide range of benefits, which have led several countries to explore and even embrace this operational mode, supporting its development and integration into their energy systems.

Benefits of Islanded Operation:

• Enhanced Reliability: Islanded mode operation localises power supply, reducing the impact of grid-wide disturbances and improving overall reliability.
• Critical Services Protection: Ensures uninterrupted power to essential services and infrastructure (e.g., hospitals and data centres), crucial during widespread grid outages.
• Stability: It allows for better control over grid stability by isolating the islanded segment from external fluctuations and disturbances.
• Renewable Integration: Facilitates the efficient use of local renewable energy sources, contributing to sustainability and reducing reliance on non-renewable resources and grid imports.
• Cost Savings: Offers potential economic benefits through optimised local energy management, reducing transmission losses and avoiding costly infrastructure upgrades.

Countries that support Islanded Operation:

• United States: Various states within the US, particularly those with high levels of renewable penetration, like California and Hawaii, have developed regulations and support mechanisms for microgrids and islanded operations to ensure energy reliability and sustainability.
• Australia: Given its vast geography and remote communities, Australia has implemented several islanded and microgrid solutions, especially in off-grid and edge-of-grid locations, to provide reliable and sustainable energy.
• Japan: Following the Fukushima disaster, Japan has increased its focus on energy resilience, supporting the development of microgrids and islanded operations to enhance local energy security and disaster preparedness.
• Spain is advancing in island operations, particularly in its island regions, to integrate renewable energy sources and improve grid stability. The country's focus on sustainable energy solutions supports the development of microgrids that enhance resilience against mainland grid disturbances.
• Greece: In Greece, islanded operations are pivotal for electrifying remote islands and leveraging the nation's abundant solar and wind resources. This strategy secures a stable energy supply for isolated areas and aligns with Greece's goals for renewable energy adoption and grid modernisation.
• United Kingdom: The UK has taken significant steps towards supporting the islanded operation, demonstrated within the Distributed ReStart project led by National Grid ESO. This initiative marks a pioneering move to explore how distributed energy resources can aid in restoring power in a major outage, laying the groundwork for future islanded and autonomous grid capabilities.

Join the Dialogue for self-sustained power islands

As the energy sector evolves towards a more resilient and flexible future, the role of islanded operations in enhancing grid reliability and sustainability cannot be overstated.

Our solution, Omega suite, is at the forefront of grid management software, designed to facilitate the seamless integration and optimisation of islanded operations. Notably, the Omega suite has been successfully deployed in a groundbreaking project with Iberdrola in Spain, marking a significant milestone in remote synchronisation capabilities within distribution networks. For more information on our collaboration with Iberdrola and the innovative strides in grid synchronisation, please visit the Iberdrola website and our website to read the relevant case study.

We invite stakeholders across the energy sector to explore how Omega Suite can support your transition to more autonomous and efficient grid management. Contact us to learn more about how SMPnet can empower your grid operations.