Synchronverters or virtual synchronous generators are inverters which mimic synchronous generators to provide “synthetic inertia” for ancillary services in electric power systems.
Figure 1. A simple diagram of Synchronverter operation environment
Background
Standard inverters are very low inertia elements. During transient periods, which are mostly because of faults or sudden changes in load, they follow changes rapidly and may cause a worse condition, but synchronous generators have a notable inertia that can maintain their stability.
Recently by using more and more renewable energies, especially solar cells, more inverters have been used in grids and because of mentioned reason, this could endanger power system reliability.
History
Hydro-Québec began requiring synthetic inertia in 2005 as the first grid operator. To counter frequency drop, the grid operator demands a temporary 6% power boost by combining the power electronics with the rotational inertia of a wind turbine rotor. Similar requirements came into effect in Europe in 2016.
Synchronverter Model
Synchronverter structure can be divided into two parts: power part (see figure 2) and electronic part. The power part is energy transform and transfer path, including the bridge, filter circuit, power line, etc. The electronic part refers to measuring and control units, including sensors and DSP.
Figure 2. Power part of a synchronverter
The important point in modeling synchronverter is to be sure that it has similar dynamic behavior to Synchronous generator (see figure 3). This model is classified into 2-order up to 7-order model, due to its complexity. However, 3-order model is widely used because of proper compromise between accuracy and complexity.
where
Figure 3. The per-phase model of an SG connected to an infinite bus
Source from Wikipedia