SUREVIVE – Stability Tests for Momentary Reserve Provision from Distribution Network Annexes

Pilot Testing of Grid-Forming Inverters (GFMI) in the Distribution Grid

In the course of the energy transition, the share of power converter-based generation plants in the electricity grid is increasing rapidly, while at the same time conventional power plants are being taken off the grid. This poses new challenges for system stability, in particular due to the disconnection of conventional grid-forming plants and the reduction of the effective short-circuit ratio.

The German Federal Ministry for Economic Affairs and Energy (BMWE) roadmap for system stability stipulates that power converter-based systems must also contribute to grid stability in the future. In order to gain practical experience with GFMIs in real distribution grids at an early stage, the SUREVIVE project is conducting a field test with several decentralized GFMIs.

The pilot systems will be connected at the HV/MV substation level, where the first grid-forming systems will be introduced via market-based procurement processes starting in 2025. Starting in 2027, comprehensive integration of grid-forming systems is also planned through the specification of minimum technical requirements.

Project Objectives:

• Investigation of the interaction and stability of GFMIs in the distribution grid under real conditions
• Derivation of findings for the overall system with high penetration of grid-forming properties from the distribution grids
• Creation of a best practice guide for grid operators, project developers, and certifiers to accelerate the integration of GFMI installations
• Developing business models for providing instantaneous reserve in the distribution grid
• Continuously incorporating the insights gained into product development, technical requirement definitions, and market-based procurement processes

Preparation:

• Grid connection assessment for separate trial operation and parallel operation with the regular distribution grid
• Developing a grid and system integration concept
• Simulations and laboratory tests for risk-minimizing test planning

Field Test:

Field test with several battery-based GFMIs in the multi-MW class at grid level 4 under the conditions of a real German distribution grid, including existing plants (fig. 1):

• Commissioning of the participating test facilities in a separate test grid and in parallel operation with the regular distribution grid
• Tests with special excitation to evaluate and identify contributions of GFMIs to local and global system stability as well as stability and interoperability risks for and caused by GFMIs in the distribution grid
• Continuous tests to evaluate operational excitation and availability for market activities
• Scientific evaluation and exploitation of the tests for model validation and further development

Generalization:

Develop and evaluate tools for stability assessment for GFMIs in the distribution grid:

•  Scientific development and derivation of approaches for various grid situations and high penetration scenarios
• Create and evaluate pragmatic approaches for distribution grid operators for short-term use and for medium-term high penetration scenarios

Business Case:

Develop and evaluate approaches for the economic viability of GFMIs at the distribution grid level:

• Develop and evaluate robust business models for plant operators at the distribution grid level by interlinking the instantaneous reserve as a system service with the existing markets
• Evaluate the local added value of grid-friendly operation of GFMIs and make it usable to increase the absorption capacity of the distribution grid

Documentation:

• A best practice guide for connecting and operating GFMIs in distribution grids for plant manufacturers, project developers, installers, and operators, as well as distribution grid operators, will be created and discussed with stakeholders to enable the widespread establishment of GFMI as quickly and efficiently as possible
• Stimulate industry dialogue on GFMI and continuously integrate current developments into the project