Elastic Links: Pioneering Flexible Connections for Enhanced Distribution Grid Performance

Flexible connections in distribution grids, such as SOPs and MVDC links, enhance grid flexibility, reliability, and efficiency, facilitating overall grid management.

Introduction to Advanced Flexible Connections

Distribution grids are profoundly transforming as we navigate the era of increased digitalisation and renewable energy integration.The need for more robust, flexible, and efficient power systems has never been greater. Advanced flexible connections, such as Soft Open Points (SOPs), Medium Voltage Direct Current (MVDC) links, and Hybrid systems, are at the forefront of this evolution, offering promising solutions to the challenges faced by traditional grid architectures.

With full spectrum οf active and reactive power capabilities,grids can dynamically manage power flows, optimise energy distribution, and maintain stability, even under the fluctuating conditions typical of renewable energy sources. Moreover, these systems facilitate a more decentralised approach to energy management, where local generation and consumption are balanced more efficiently and reliably.

These connections promise substantial promise for distribution grids. They can handle higher loads and integrate diverse energy sources while improving the overall resilience and reliability of the power supply. This transformative capability enables grids to be more responsive to changes in demand and generation, paving the way for a sustainable and energy-efficient future.


FlexibleConnection Topologies in Distribution Grids

Flexible connection technologies enhance the operational capabilities of distribution grids and address the growing complexity of energy management in an era of rapid technological change. Below (also depicted in Figure 1), we explore three pivotal flexible connection architectures that are reshaping the landscape of modern power distribution systems, each offering a different angle to specific needs and challenges within the grid.

Overview of flexible connection architectures.

Soft Open Points (a): This configuration uses back-to-back converters to connect two AC grids through a DC link. Soft Open Points (SOPs) enable flexible power flow and voltage control, enhancing the grid's ability to integrate renewable sources and manage load variations dynamically. They are pivotal in transforming traditional passive distribution networks into active ones, facilitating improved reliability and efficiency.

MVDC Links (b): Medium-voltage Direct Current (MVDC) links also use AC-DC-AC converters but are typically structured with a direct link (cable or overhead line)between the converters. This setup is advantageous for long-distance power transmission within the distribution network, providing better control overpower flows and reducing losses compared to traditional AC systems.

Hybrid Systems (c): Hybrid systems combine the features of SOPs with additional functionalities like integration of renewable energy sources (e.g.,solar panels), energy storage units, and advanced monitoring systems. This configuration supports the basic functionalities of voltage and power controland enhances grid resilience and adaptability to varying energy demands and generation profiles. Other variations of hybrid systems include the formation of multiple terminals.

The benefits ofintegrating flexible connections


Integrating flexible connections at the distribution level offers multiple benefits and applications, addressing key operational challenges and enhancing overall grid performance. These advanced technologies provide significant advantages in several areas: 

Planning and Dynamic Services Provision: Flexible connections enable more efficient and effective grid planning. By dynamically adjusting power flows and voltage levels, these technologies allow for better accommodation of new loads and renewable energy sources. This leads to optimised use of existing infrastructure and deferred investments in new assets.

Feeder Load Balancing: One critical function of flexible connections, such as SOPs, is to balance the load among different feeders. This ensures that no single feeder is overloaded, improving the overall reliability and efficiency of the distribution network​​.

Network Reconfigurations: Flexible connections facilitate dynamic reconfiguration of the network, such as forming ring topologies. This enhances the grid's resilience and reliability by providing multiple pathways for powerflow, which is particularly beneficial during fault conditions and natural disasters.

Voltage Profile Improvement: Maintaining an optimal voltage profile across the distribution network is crucial for ensuring the quality of power suppliedto consumers. Flexible connections help manage and stabilise voltage levels, improving the voltage profile and reducing the risk of voltage-related issues​​.

Three-Phase Balancing: Many distribution networks need to be more balanced between the three phases, which can lead to inefficiencies and increased losses. Through their advanced control capabilities, flexible connections can mitigate these imbalances and enhance the network's performance​​.

DG Hosting Capacity Enhancement: As more renewable energy sources are integrated into the grid, the ability to host distributed generation becomes increasinglyimportant. Flexible connections increase the grid's hosting capacity by managing power flows and preventing issues such as voltage violations and thermal overloads​​.

Supply Restoration: In the event of a fault, flexible connections can rapidly restore supply to affected areas by rerouting power through alternative pathways. This significantly improves the grid's resilience and reduces downtime for consumers​​.


Challenges of Implementing Flexible Connections


Flexible connections in distribution grids offer numerous benefits, but their implementation has several challenges. These challenges must be carefully considered and addressed to maximise the effectiveness and reliability of flexible connection technologies. Key challenges include:


Capacity & Locations Selection: Selecting the appropriate capacity for SOPs and other flexible connections is crucial. The capacity must be sufficient to handle expected load variations and power flows without causing congestion or instabilities. This requires detailed load forecasting and scenario analysis to ensure that the chosen capacity can accommodate future demands and integrate distributed generation sources​​. Determining the optimal points in the network for installing flexible connections involves complex planning. This includes considering factors such as current load profiles,voltage levels, and the locations of distributed energy resources. Effective siting ensures that these technologies can provide maximum benefits in load balancing, voltage regulation, and fault management​​.

Maturity of the Technology: While technologies like SOPs are quite mature and have been successfully implemented in various pilot projects, ongoing advancements continue to improve efficiency and functionality. Nevertheless, each deployment must be tailored to the specific conditions of the distribution network, which can present challenges in terms of customisation and integration​​.

Technical Considerations: The design and architecture of flexible connection smust be compatible with existing grid infrastructure. This includes considerations for space requirements, thermal management, and integration with current control systems. Additionally, minimising power losses is a critical objective. SOPs and MVDC links must be designed to operate efficiently, which involves selecting appropriate components and optimising control strategies to reduce conversion and transmission losses​​. Last but not least, ensuring the reliability of these systems requires robust design and rigorous testing.Redundant systems and fail-safes must be in place to maintain grid stability during component failures or unexpected load conditions​​.

Requirement for Digital Infrastructure: Implementing flexible connections requires a robust digital infrastructure, including reliable communication networks and advanced control systems. This infrastructure supports real-time data exchange and coordinates control of grid components.High-speed, secure communication channels are essential for effectively operating SOPs and MVDC links, enabling them to respond quickly to changing grid conditions​​. This also extends to the requirement of PMUs, which are crucial for monitoring the state of the grid and providing the precise data needed for the optimal operation of flexible connections. They offer high-resolution measurements of voltage and current phasors, which are essential for dynamic system analysis and real-time control. Deploying PMUs across the grid ensures that flexible connections can be managed effectively, improving stability and performance​​. 

Control Aspects and Integration with Other Grid Management Software. Effective control mechanisms are essential for successfully implementing flexible connections in distribution grids. These control systems,including centralised, decentralised, and local approaches, ensure operational efficiency, reliability, and responsiveness. However, these control systems must be integrated with other grid management software for distribution grids. By seamlessly orchestrating flexible connections with these systems, utilities can enhance grid reliability, improve operational efficiency, and support the dynamic management of distributed energy resources. Advanced analytics and robust communication networks are vital in this integration, facilitating real-time data exchange and decision-making across the grid.

Addressing these challenges through careful planning,advanced technology integration, and robust digital infrastructure can fully realise the benefits of flexible connections in distribution grids.

Roadmap of Flexible Connections


Flexible connections in distribution grids are being deployed globally to enhance grid flexibility, reliability, and efficiency.This section provides an overview of current deployments and future projects,detailing where and when these technologies are being implemented and theircapacities and objectives.


Current Deployments


China: Since 2018, China has implemented several multi-terminal SOPs in cities like Beijing, Suzhou, Hangzhou, and Tianjin. These installations range from three-terminal to four-terminal configurations, utilising both AC/DC and DC/DC converters. These projects aim to efficiently integrate DC power loads and generation into public distribution networks.

United Kingdom: The UK has proactively deployed SOPs through various projects funded by Ofgem. Notable projects include:

o  Flexible Urban Network-Low Voltage (FUN-LV) Project (2014-2016) - Aimed at sharing capacity between substations to improve load balancing and voltage

o  Network Equilibrium (2015-2019): Focused on optimising SOPs for balancing loads and enhancing voltage profiles across the network.

USA: In the USA, projects like Eagle Pass (2011) and Mackinac HVDC Flow-Control(2014) have demonstrated the use of back-to-back SOPs to improve grid performance. These projects highlight the capability of SOPs to manage powerflows and integrate renewable energy sources effectively.

Japan: Japan has been at the forefrontof deploying SOPs for load balancing and voltage improvement. Notable implementations include:

o  6.6kV/1MVADual-Terminal SOP: Installed in a test distribution network to connect two distribution lines, aimed at improving load balancing and voltage stability​​​​.

o  Microgrid Demonstration Projects: These projects focus on integrating SOPs within microgrids to enhance resilience and effectively manage local generation andload​​.


Future developments in flexible connections for distribution grids are set to expand globally, with countries like the UK,China, Germany, and Japan leading the way. The UK’s Active Response Project optimises capacity and enhances grid reliability through SOPs and UPFC-based SOPs. China continues to develop advanced multi-terminal SOP configurations for urban and rural settings. Germany focuses on integrating SOPs with advanced control systems to manage high renewable penetration. Japan plans to expand SOP deployments within microgrids, integrating renewable energy and storage systems for greater resilience. These initiatives reflect a concerted effort to leverage flexible connection technologies to create more adaptable, efficient,and sustainable power grids worldwide.


Joining theConversation: Orchestrating SOP with Grid management software


The integration of flexible connections with advanced grid management software like Omega Suite is a critical step towards realising their full potential in modern distribution grids.This integration supports dynamic distributed energy resource management, enabling utilities to respond swiftly to changing grid conditions and maintain stability. Leveraging advanced analytics and robust communication networks ensures that flexible connections operate efficiently within the broader grid framework, promoting a more resilient andefficient power grid.

SMPnet's grid management suite

Sources & Additional reading:


·      E.Olea-Oregi, P. Eguía-López, A. Sanchez-Ruiz and I. Loureiro-González,"Industrial Overview of Back-to-Back VSC Power Links in MV DistributionNetworks," in IEEE Transactions on Smart Grid, vol. 14, no. 1, pp.126-141, Jan. 2023,

·      X.Jiang, Y. Zhou, W. Ming, P. Yang and J. Wu, "An Overview of Soft OpenPoints in Electricity Distribution Networks," in IEEE Transactions onSmart Grid, vol. 13, no. 3, pp. 1899-1910, May 2022,