The energy transition is a central topic of debate across the Nordic region. In Sweden, discussions about the future energy mix are particularly active, weighing the merits of different decarbonization pathways. While renewable energy sources (RES) like wind power are an attractive clean solution, their large-scale integration presents new and significant technical challenges to the operational security of the power grid. The inverter-based nature of these resources displaces conventional synchronous generators, reducing the system's overall inertia and short-circuit strength. In contrast, nuclear energy is increasingly considered a counterpart, which, from a grid integration perspective, comes with fewer new technical challenges. This context makes it imperative to find effective technical solutions to support the grid if a high penetration of RES is to be achieved reliably.

The primary goal of this paper is to investigate, quantify, and compare the effectiveness of two advanced power electronic solutions - Battery Energy Storage Systems (BESS) and the enhanced STATCOM (E-STATCOM) - in mitigating these stability challenges and supporting the large-scale integration of wind power. The study aims to provide a clear performance assessment of these technologies, offering valuable insights for Transmission System Operators (TSOs) and wind farm developers on their optimal application for enhancing grid reliability.

Overall, this study contributes to the discussion on how large-scale wind power can be integrated into the Nordic system when its adoption is complemented by devices that can also provide power quality support. While the integration of wind power on its own changes the traditional paradigm of operating power systems, this study demonstrates how these complementary technologies introduce new tools to manage this paradigm shift.

Methodology

To achieve a comprehensive assessment, a two-part study was conducted, combining system-wide analysis with detailed component-level compliance verification.

The first part involved a Nordic system study using the DIgSILENT PowerFactory. A detailed model of the Nordic transmission grid was used to simulate various disturbance scenarios. This system-level analysis focused on demonstrating the overall benefits of BESS and E-STATCOM to system stability, particularly in response to critical faults. Furthermore, a high-level analysis was performed to establish selection criteria for deploying each technology, comparing their capabilities in providing services such as synthetic inertia, Fast Frequency Response (FFR), and dynamic voltage support for the transmission grid.

The second part of the study focused on Grid Code Compliance assessment at the point of connection of a wind farm. Using PSCAD/EMTDC and a benchmark framework publicly provided by the Danish TSO, Energinet. This part of the study focused on evaluating the performance of a wind farm under various configurations:

Standalone grid scale wind plant

Grid scale wind plant with a BESS system

Grid scale wind plant with a Grid-Forming (GFM) STATCOM

Grid scale wind plant with an E-STATCOM (GFM STATCOM with super capacitors for energy storage).

The simulations tested the configurations against key technical requirements stipulated in the grid codes applicable in the Nordic region, focusing on aspects like fault-ride-through (FRT), voltage support, and frequency control.

Results and Conclusions

The results from the PowerFactory simulations demonstrate the strong technical performance of both BESS and E-STATCOM in significantly enhancing the stability of the Nordic grid. The paper not only showcases these technical capabilities but also provides an insightful discussion on how the solutions differentiate. This comparison is framed from both a technical services perspective—analysing their roles in providing broad grid support versus specific ancillary services—and from an energy market perspective, considering their distinct value propositions.

The PSCAD compliance studies further revealed the benefits of these technologies at the generation asset level. While a modern wind farm is expected to meet many grid code requirements on its own, its performance during severe grid disturbances is substantially improved with the addition of supporting technologies. Both BESS and E-STATCOM enabled the wind farm to pass the most stringent grid code tests with considerable margins, ensuring reliable operation and enhanced stability.

The paper concludes that while both technologies are highly beneficial, their optimal deployment depends on the specific grid needs. It provides valuable insights, supported by simulation results, to aid stakeholders in selecting the most appropriate and cost-effective solution for ensuring operational reliability for large scale wind power.