Characterization of the Grid-Forming Function of a Power Source Based on its External Frequency Smoothing Capability

In upcoming converter dominated power systems, some devices wm be required to function as grid forming to ensure stability. Several control schemes have been proposed in the literature and future systems might include a mixture of them, attending that they fulfill grid codes to be defined. Here is presented a method that derives a simple model based on basic properties expected from grid forming devices from a system point of view. This model serves to define necessary conditions on local frequency smoothing capability to claim grid-forming function in a power system. One application case is proposed to discriminate between the so-called “grid forming controls” and “grid following controls on the basis of their external behavior rather than from their control structure. Eventually, a cost implication in terms of storage size requirement is discussed. This novel point of view on grid-forming control will certainly help TSOs to specify their needs and anticipate the costs for the upcoming transition.