Bold Moves Needed: How Hybrid AC/DC Grids Could Be the Key to Energy Resilience

Introduction

In a rapidly evolving energy landscape, where resilience and renewable integration are paramount, one key technology remains largely overlooked: hybrid AC/DC grids. These innovative systems, which merge traditional AC power networks with DC microgrids, hold the promise of transforming the way we manage distributed energy resources (DERs). Hybrid AC/DC grids can offer superior resilience, greater efficiency, and more effective integration of renewables—yet they remain on the fringes of practical implementation.

Why has the energy sector been so slow to adopt this transformative approach? Despite the clear advantages, hybrid AC/DC grids are still constrained by outdated infrastructure, regulatory inertia, and a deeply embedded preference for familiar AC-only frameworks. This hesitation not only stifles innovation but also leaves the grid vulnerable to the increasing complexities of distributed energy integration and the unpredictability of renewable power. It’s time to challenge these conventions, push the boundaries, and unlock the full potential of hybrid AC/DC grids as we redefine the future of energy resilience and sustainability.

Introducing the Hybrid AC/DC Grid

To truly understand why hybrid AC/DC grids represent a significant leap forward, it’s essential to look at how they operate and what makes them different from traditional grid configurations. Hybrid AC/DC grids are a marriage between conventional AC systems and DC grids, enabling seamless integration of DERs like solar panels, battery storage, electric vehicle chargers, and other DC-powered devices. This combination allows these different forms of energy to be managed in a way that optimises both resilience and efficiency.

The diagram below illustrates a typical setup of a hybrid AC/DC grid. As shown, traditional AC feeders are connected to AC/DC converters, which then link to various DC integrations. These DC subsystems might include DC loads, batteries, solar panels, or even charging stations for electric vehicles. Such a design reduces conversion losses when directly utilising renewable DC power sources, improves reliability, and allows for better load management.

In a conventional AC-only power system, integrating DC devices like solar panels or batteries typically requires multiple conversions between AC and DC, leading to inefficiencies. In contrast, hybrid AC/DC grids simplify these connections, reduce conversion losses, and ultimately lead to a more resilient and adaptable power system. By taking advantage of both AC and DC power’s inherent strengths, hybrid grids can dynamically adjust to changing energy demands and facilitate smoother integration of renewable energy sources, while reducing strain on the AC infrastructure.

Benefits of Hybrid AC/DC Grids for Resilience and DER Hosting Capacity

As the energy sector continues to face increasing pressure from rising renewable integration, growing load demands, and more frequent extreme weather events, the resilience and flexibility of the grid are paramount. Hybrid AC/DC grids present a promising solution to these challenges, particularly when it comes to managing DERs and enhancing overall grid resilience. Below, we explore the specific benefits of hybrid AC/DC grids, focusing on their potential to improve resilience and expand DER hosting capacity.

• Enhanced Resilience During Peak Demand and Contingencies: Hybrid AC/DC grids improve resilience by flexibly managing power flows between AC and DC systems, especially during peak loads or extreme weather. They leverage DC-connected resources like energy storage to stabilise the grid during contingencies, providing dynamic load management and mitigating feeder overloads. These systems can quickly reroute power to help the network withstand and recover from disturbances, directly aligning with Con Edison’s goals of enhancing dependability during outages.

• Increased Hosting Capacity for DERs: Hybrid AC/DC grids can significantly increase DER hosting capacity by addressing the challenges faced by traditional AC grids, such as reverse power flow and conversion inefficiencies. By adding a DC layer, DERs like solar panels and batteries can be connected directly to the DC bus, reducing energy losses and improving stability. This integration mitigates reverse power flow and minimises voltage fluctuations, enabling greater renewable capacity without major infrastructure upgrades.

• Improved Voltage Regulation and Load Balancing: Hybrid AC/DC grids simplify voltage regulation and load balancing by integrating DC-tied storage and direct DER connections, eliminating the need for complex AC-only regulation methods. Advanced controllers dynamically control active and reactive power, maintaining stability despite fluctuating demand. This model ensures real-time coordination between DERs, storage, and feeder systems, providing proactive load management and improved grid health.

• Optimised Power Flow and Reduced Costs: Hybrid grids optimise power routing by reducing unnecessary AC/DC conversions, minimising energy losses and improving efficiency. The use of multi-terminal DC-tied systems supports flexible power routing, effectively managing excess renewable generation by storing energy in DC batteries and dispatching it to AC loads. This reduces the need for system upgrades, thus lowering interconnection costs for both utilities and DER developers.

• Flexibility for Future Expansion and Scalability: Hybrid AC/DC grids are adaptable to future energy demands, allowing scalable integration of DERs, storage, and EV chargers. Their AC and DC pathways enable utilities to expand infrastructure in a cost-effective, non-disruptive manner, supporting phased deployment and ensuring grid improvements keep pace with technological advances while maintaining reliability. This flexibility aligns with the tender’s emphasis on testing, validation, and gradual rollout.

• Islanding Capabilities for Enhanced Resilience: Hybrid AC/DC grids effectively support intentional islanding, allowing sections of the grid to operate independently during disruptions, which enhances resilience. DC resources like batteries and solar PV ensure that critical loads stay powered, while AC/DC converters maintain voltage and frequency stability for smooth transitions. This capability helps manage peak demand and reduces stress on the main grid by enabling localised autonomy.

Why Aren’t Hybrid AC/DC Grids Everywhere Yet? Unpacking the Challenges

Despite their promise, hybrid AC/DC grids have not been widely deployed due to significant technical, operational, and regulatory challenges. While the benefits are clear, these barriers have slowed large-scale adoption and highlighted areas needing innovation.

• Complexity of Fault Management Across AC and DC Sides: Fault management in hybrid AC/DC grids is complex, as faults can occur on both the AC and DC sides, each requiring different approaches. AC fault handling is mature, but DC faults propagate quickly and need specialised converters and fast-switching DC breakers. Developing an effective fault management strategy that addresses both sides of the grid remains a key hurdle.

• Interlink Converter Control—Managing 4-Quadrant Operation: Interlink converters must manage active and reactive power in both import and export modes (four quadrants), requiring precise control algorithms. These converters are crucial for balancing power and maintaining grid stability, but achieving reliable four-quadrant control is challenging. Instability in these converters could lead to significant disruptions, making their control a key obstacle to wider adoption.

• Orchestration and Coordination of Diverse Assets: Hybrid AC/DC grids integrate a mix of DERs, energy storage, and AC/DC feeders, requiring sophisticated coordination. Controllers must dispatch power (active and reactive), maintain grid stability, and balance AC/DC flows in real-time, while managing different asset characteristics. The complexity of orchestrating diverse assets makes effective deployment a challenging task.

• Interoperability and Protocol Challenges: The lack of standardisation among devices from different manufacturers complicates interoperability in hybrid grids. Different communication protocols create barriers, leading to a “tower of Babel” where coordination between SCADA, DERMS, local controllers, IEDs and other systems becomes cumbersome. Without unified communication standards, integration remains difficult and costly.

• Ownership and Operational Coordination: Hybrid grids involve complex ownership structures, with assets owned by utilities, customers, and third parties. Conflicts arise when coordinating shared assets, like customer-owned batteries being reserved for private use versus grid stability needs. Synchronising priorities and control among different stakeholders requires new agreements and regulatory frameworks, which are still underdeveloped.

• Regulatory and Market Barriers: Current regulations are largely designed for traditional AC systems, with few provisions for hybrid AC/DC environments. Issues such as grid access, DER compensation, and cost-sharing need new frameworks that address the hybrid model. The financial uncertainties and lack of clear regulatory support deter investment in hybrid AC/DC projects.

The Role of Advanced Control Systems and Digital Twins in Hybrid Grids

To address the challenges of hybrid AC/DC grids and unlock their full potential, advanced control systems and digital twins have emerged as critical tools. These technologies provide the sophistication and real-time responsiveness needed to manage the complexities of hybrid grids effectively.

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• Strategic Centralised Controllers: To effectively manage hybrid grids, centralised controllers should be deployed at strategic nodes within the system. These controllers serve as the key points of orchestration and control, overseeing the operation of both AC and DC segments of the network. Positioned at critical locations, centralised controllers enable efficient monitoring and control of multiple distributed assets, ensuring optimal power distribution, reducing response times during contingencies, and enhancing the overall stability of the hybrid grid. By strategically placing these centralised controllers, hybrid grids can better manage power flows, optimise asset utilisation, and respond swiftly to both planned and unplanned events.

• Advanced Control Systems for Real-Time Coordination: Hybrid grids require advanced control systems to integrate AC and DC power, DERs, and storage into a cohesive network.  A hierarchical control architecture—operating on primary, secondary, and tertiary levels—ensures stable device-level operation, coordinates multiple assets like AC/DC converters, and optimises broader grid efficiency. Together, these systems maintain 4-quadrant operation, manage power flows, and provide rapid responses to fluctuating conditions.

• The Power of Digital Twins for Optimisation and Predictive Control: Digital twins, virtual models of physical grid assets, are crucial for optimising hybrid AC/DC grids. They simulate system behaviour to predict outcomes of control strategies, allowing for better decision-making. For example, digital twins can help optimise interlink converters for balancing power and mitigate instabilities. They are also valuable for predictive maintenance, anticipating faults before they occur and reducing downtime, which is particularly useful for managing complex converters and DC breakers.

• Enhanced Contingency Management and Fault Response: Advanced control systems and digital twins enhance contingency management by quickly assessing and responding to faults, minimising cascading failures. Digital twins simulate potential contingencies, helping controllers make informed decisions in real-time to stabilise the hybrid grid during disruptions.

• Facilitating Interoperability and Standardisation: The diversity of components in hybrid grids makes interoperability challenging. Advanced control systems bridge these gaps with robust protocols, ensuring effective communication between SCADA, DERMS, microgrid controllers and other IEDs.

• Optimising Multi-Ownership Assets: Hybrid grids often involve assets owned by different stakeholders—utilities, customers, and third parties. Advanced control systems and digital twins help manage ownership complexities by monitoring assets, prioritising commands, and balancing the needs of stakeholders. They ensure that resources, like customer-owned batteries, are used optimally for both individual and grid stability purposes.

Conclusion

As hybrid AC/DC grids continue to emerge as a vital solution for modern power distribution challenges, it’s clear that effective control, integration, and optimisation are crucial for realising their full potential. At SMPnet, we are at the forefront of these advancements, offering innovative solutions tailored to the dynamic control and orchestration of integrated AC/DC grids.

If you are looking to scale renewable integration, reduce operational costs, or enhance grid resilience, our Dynamic Control and Orchestration Solution for Integrated AC/DC Grids is designed to meet these needs. We invite utilities, energy developers, and stakeholders to partner with us in this transformative journey. Let’s work together to shape a sustainable and resilient energy future.

For more details on our solution and how it can address your specific needs, please visit our Dynamic Control and Orchestration of Integrated AC/DC Grids page.

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