Asymmetric Contributions to Instantaneous Reserve by Generation, Loads, and Storage

In the course of decarbonization, interconnected systems will have to be prepared for recurring situations during which they are fed by mostly inverter-based generation. Today, the stabilizing influence of the rotating masses directly coupled to the grid via synchronous generators on every frequency change is essential. The inherent immediate reaction of synchronous generators on voltage-angle changes and frequency variations is called instantaneous reserve. During dynamic situations such as load or generation changes and particularly during the first second after a system split, any active-power imbalance must initially be compensated by instantaneous reserve. Inherent power-electronic contributions to instantaneous reserve become essential for future situations with abundant renewable feed-in. The generic concept of a virtual synchronous machine (VSM) includes inherent instantaneous reserve but, like for a synchronous machine, the active-power reaction of a VSM is symmetric on positive and negative frequency variations. The immanent characteristics and limitations of possible VSM-coupled grid participants such as photovoltaic plants, storages, charging infrastructure, and different kinds of loads are oftentimes asymmetric in this respect. This article describes a novel concept of modifications to a generic VSM control scheme enabling asymmetric and even unidirectional contributions to inherent instantaneous reserve. Thus modifying future converters of generators, storages, and different kinds of loads, with an emphasis on charging systems of electric vehicles, can tap potentials unused up to now. Thereby, increased effort (e.g., extra storage, higher ampacity of the semiconductors) for making contributions symmetric can be avoided to a great extent.