Publications -

Reports

Definition of a standard process for interaction studies with EMT simulation in multi-vendor projects

April 2025

The successful development of multi-vendor, multi-terminal HVDC systems relies on a robust process for conducting interaction studies that help mitigate interoperability risks.

The InterOPERA partners have come together to define this process and provide a comprehensive guideline that addresses the technical, temporal, and organisational aspects of these studies.

This report addresses key questions, including:

Are additional studies required compared to the existing process for single-vendor, point-to-point projects?
Should these studies be organised and categorised differently?
When should they be performed and based on which data and models?
How can we effectively iterate on these studies through joint cooperation among all parties?

Functional requirements for HVDC grid systems and subsystems

April 2025

InterOPERA has released the second version of the Functional requirements for HVDC grid systems and subsystems, offering a technology-agnostic description of the functional requirements for multi-terminal HVDC systems and subsystems.

Subsystem-level functions – which can be achieved by different technical solutions – are the most susceptible to cause adverse interactions. Therefore, these functions are formulated as verifiable requirements that each subsystem must meet at the DC points of connection, allowing different technical solutions to coexist.

The report details key functional requirements crucial for interoperability, including the DC-FRT requirement for AC/DC converters, the DC fault separation requirement for DC switching stations, and the dynamic and stability performance requirements for AC/DC converters. The applicability and validity of these functional requirements are evaluated using the InterOPERA demonstrator grid simulations to verify the effectiveness in mitigating interoperability issues.

Platform requirements for offline and real-time simulations

March 2025

InterOPERA has released Platform Requirements for Offline and Real-Time Simulations, a new report detailing essential guidelines for system operators, integrators, and EMT tool developers to perform interaction studies with multi-vendor, multi-terminal HVDC systems, including those connecting offshore wind parks.

The report outlines minimum requirements for hardware, software, and organizational setups needed for interaction studies. The requirements are categorized for offline (LAB-OFF), real-time (LAB-RT), and shared (LAB-COM) needs, along with standards for selecting ElectroMagnetic Transients (EMT) tools.

This resource offers system operators and integrators a clear framework for enhancing interoperability and reliability in HVDC grids.

Requirements for AC/DC converter stations, DC switching stations, Power Park modules and DC Grid controller offline models, SIL models and C&P cubicles

March 2025

The successful development of multi-vendor, multi-terminal HVDC grids hinges on having robust HVDC and wind power plant models and replicas that ensure seamless interoperability.

InterOPERA partners have collaboratively defined a comprehensive set of minimum requirements to guide the creation and use of these models and replicas while:

addressing key challenges such as balancing accessibility with IP protection
ensuring long-term usability, maintaining high performance, and
providing thorough documentation for practical application.

This detailed effort has culminated in this report prepared by the experts of Work Package 1. It outlines around 150 well-justified and self-assessed requirements, designed to facilitate their effective dissemination and implementation.

InterOPERA Multi-Party Cooperation Framework – Draft version

December 2024

InterOPERA has released the second version of the Multi-Party Cooperation Framework, incorporating the last consultations and contributions of the Parties.

This framework facilitates the coordination among the stakeholders in the development and operation of MVMT HVDC grids. It focuses on ensuring HVDC systems are inherently compatible, mitigating interoperability risks, enhancing the grid-forming capabilities of offshore and onshore converters, improving offshore network planning, and developing strategic and operational tools to support the integration and growth of these grids.

Summary report from the 2^nd technical workshop

November 2024

This is the summary report from the 2nd technical workshop that took place on 28 August. This was the second out of a series of six technical workshops with the members of the InterOPERA Stakeholder Committee. These workshops give the opportunity to organisations impacted by the project to provide feedback and contribute to shaping the InterOPERA deliverables.

During the in-person workshop, the members of the Stakeholder Committee discussed and provided inputs on three reports:

Functional requirements for HVDC grid systems and subsystems.
Grid-Forming Functional Requirements for HVDC Converter Stations and DC-Connected PPMs in Multi-Terminal Multi-Vendor HVDC systems.
Definition of a standard process for interaction studies with EMT simulation in multi-vendor projects.

Assessment of two DC voltage droop options for small-signal stability in MMC-based Multi-Terminal DC Grids

October 2024

The interoperability of vendor controls is crucial to the success of multi-vendor, multi-terminal DC systems. This report delves into this by assessing two DC voltage droop control strategies designed to maintain small-signal stability in Modular Multilevel Converter (MMC)-based multi-terminal DC grids.

Key findings from the study:

DC voltage droop control significantly influences the dynamics of multi-terminal DC grids (MTDC).
Two DC voltage droop control strategies can coexist in a multi-terminal DC grid, despite some limitations regarding dynamic performance.
DC reactors, essential components of DC circuit breakers, can negatively affect the damping of DC voltage.

This work is a significant contribution to Work Package 2 of InterOPERA aiming to ensure the interoperability and modular design of HVDC components from various suppliers.

Functional requirements for HVDC grid systems and subsystems

June 2024

InterOPERA aims to make HVDC multi-vendor multi-terminal projects reality. But to do so, we need a functional framework that limits the risk of interoperability issues between different vendors by specifying basic operational rules for control and protection.

This report describes functional requirements for multi-terminal HVDC systems and subsystems.

The functional framework is important to limit the risk of interoperability issues between different vendors by specifying basic operational rules for control and protection.

Summary report from the 1^st technical workshop

May 2024

This is the summary report from the 1st technical workshop with the InterOPERA Stakeholder Committee that took place on 14 March 2024.

During the online workshop, the members of the Stakeholder Committee discussed and provided inputs on three reports:

Definition of standard interface and requirements for vendors’ converter models and C&P cubicles.
Minimum technical requirements for EMT offline, SIL and HIL simulation platforms and models to perform interaction studies.
Demonstrator project definition and system design studies.

Demonstrator project definition and system design studies

March 2024

The demonstrator is the centrepiece of the InterOPERA project, since it is the infrastructure that will allow interoperability between technologies from different manufacturers to be tested.

The report includes:

The assessment of the design and functionalities planned multi-terminal HVDC use-cases.
The definition of a InterOPERA demonstrator for a multi-terminal multi-vendor system.
The preliminary main circuit parameters and system design concepts for the InterOPERA demonstrator.
The preliminary system design studies for the InterOPERA demonstrator from an asset owner perspective.

Grid-forming functional requirements for HVDC converter stations and DC-connected power park modules in multi-terminal multi-vendor HVDC systems

January 2024

This report presents the project stakeholders’ view on these requirements. It will be used as a basis for the demonstration design as well as the selection of the test protocol and verification process.

Among the main findings:

Four different use cases of how grid-forming control could be applied in an HVDC system with and without support from the #windpower plants is proposed.
The importance of coordinating grid-forming control with DC voltage control is discussed and highlighted.

Multi-Party Cooperation Framework

December 2023

This report is the preliminary draft of a Multi-Party Cooperation Framework, prepared by the InterOPERA Work Package 4 “Cooperation framework and governance”.

Smooth collaboration between stakeholders is the key to unlock the potential of Multi-Vendor Multi-Terminal (MVMT) High-Voltage Direct Current (HVDC) grids.

This Cooperation Framework:

Establishes guidelines that will drive cooperation in the future MVMT HVDC project.
Defines the roles, duties, and responsibilities of the different parties.