Recently, the portion of inverter-based resources is increasing in power systems, and the role of them is getting active for a sustainable transition. In PERL, several research projects are proceeding to improve the usefulness of inverter-based resources.
Firstly, one of our projects is associated with grid-forming inverter. In particular, this project has begun with developing an inverter offering the synthetic inertia, which emulates the inertial response of conventional generators to a frequency variation. It is very important to hold the total inertia of a power system to a degree for resiliency when a conventional generator is replaced with renewable resources. Because the inverter-based resource has no mechanical inertia at all, something electrical should be prepared to supplement the loss of inertia from the retirement of conventional generators. In fact, upcoming grid-connected inverters should be more capable than conventional generators in grid-supporting operations, not just for the synthetic inertia. This type of inverter can be classified as grid-forming inverter. Because the controllability of inverter is quite excellent, the grid-forming inverter may be offering certain services that cannot be offered by conventional generators. In near future, we have a plan to demonstrate a 250kW grid-forming inverter in Biyang-do, a small island around Jeju-island. Before this demonstration, a series of our ideas are examined with hardware-in-the-loop simulations, where the grid of Biyang-do is emulated with a real-time simulator. The demonstration scale will be further increased after the small micro-grid circumstance.