ENERGIX-Stort program energi

Multi-Terminal Direct Current (MTDC) transmission matured into the most feasible technology for transmission of bulk power over long distances with cables. Thus, MTDC grids are expected to emerge in the future power grids in Europe and Japan to support energy policy objectives for integration of renewables like offshore wind energy; for strengthening the power exchanges between neighbouring countries and to create a more efficient transnational power market. However, the operational experience on interconnected Alternate Current (AC) and MTDC power grids and the availability of commercial software tools for their analysis are rather limited. This limitation in the present scenario increases planning costs and the risk of interoperability issues or instabilities during the operational phase. Existing methods and software tools for power system analysis are mostly tailored for the conventional AC transmission system. The study of mixed configurations where both AC and MTDC grids coexists can be conducted with time domain simulations and detailed models, but this approach can be limiting and extremely time consuming. The MODULATOR project main objective is to provide the industry and the research community with state-of-the- art and highly scalable software tools based on a modular approach modelling for interconnected AC and MTDC grids. The research activities are part of a cooperative project between SINTEF Energy Research, Fraunhofer IWES (Germany) and Osaka Prefecture University (Japan) within the framework of the EIG concert program. This included also a Ph.D. at Osaka Prefecture University that defended is thesis in 2021. The activities have been focused on defining and selecting the main modules of the interconnected AC/DC grid system as well as a test system to integrate the work of each of the partners in the project. Each module is being developed and implemented for the small signal models. Also, a general structure for the large signal modelling and for the optimization algorithm has been proposed. In the last project phases, an integrated workflow has been developed for optimizing the operating conditions accounting for the stability properties (small signal stability constrained optimal power flow) and tested it in a benchmark system showing its correct operation. Due to COVID-19 restrictions on travel, no exchanges have taken place during 2020. Focus on has been on dissemination via digital conferences. The project organized a final open workshop where highlights of the project have been presented with additional guest speakers from academia and industry to join the discussion. The code developed has been documented and archived and it is expected further use and development in the FME Northwind.

A main deliverable of the project has been the development of code and a workflow for performing stability assessments and optimization for interconnected AC and MTDC grids. These tools and the general ideas behind their development has been published in normal publication channels and presented in open workshops. This leads to the possibly that these approaches and part of the code developed will be more refined by the three partners or by other institutions to be operated by a larger user group. The project developed software tools that will be further applied by the project partners in future projects. For example, the small signal analysis framework developed at SINTEF will be further used also in the FME Northwind in application for offshore grids. An additional aspect to consider is that the three project participants brought different individual expertise areas to the project and that this facilitated the learning of new methods and software tools from each partner.