Maximizing the penetration of inverter-based generation on large transmission systems: the MIGRATE project

Renewable generation is mainly connected through converters. It can provide more and more services to the grid such as voltage support or frequency control. However, these services may not be sufficient for extremely high penetrations. As the share of such generating units is growing rapidly, some synchronous areas could in the future occasionally be operated without synchronous machines. In such conditions, system stability will have to be ensured with the same level of reliability as today. Presently, operation of power systems is based on the presence of synchronous machines. Frequency is linked to the balance between load and generation via the rotating masses equation. This will not be inherently valid for grids without synchronous machines. The matter of operating a network with 100 % power electronics is quite well resolved for small isolated systems. The same doesn’t apply for large transmission systems where grid topology and power injections are highly variable and are not known at every moment by all system components or even by a centralized entity. This paper describes the research that needs to be achieved to remove barriers for high penetrations of converters.