Towards Standardised Testing Procedures for Inertia Provision of Grid Forming Inverters

Grid Forming (GFM) Inverters and their capabilities are critical to enable growing penetration of Distributed Energy Resources (DER) into the electrical grid. The electrical inertia brought by GFM inverters to the network can replace or supplement the inertia of rotating machines that is a key element for power system stability. The German research project "Netzregelung 2.0" ("Grid Control 2.0") investigated the operation of power systems with GFM inverters and developed inverter controls and possible grid code compliance testing approaches. First outcomes regarding the testing approaches for inertia provision are presented. A major portion of grid-forming control approaches can be described following the well-known equations of synchronous machines and thus can also be characterized in their frequency behaviour with reference to the first order swing equation of a rotating system, mainly characterized by the acceleration time constant (Ta) and damping (D). The accurate determination of these values is important for system operators and future ancillary service markets. Measurements were performed based on existing and upcoming standards and guidelines with a special focus on parameter determination and measurement uncertainty.