Sub- and Super-Synchronous Characteristic of a Transformer Connected STATCOM Using Grid-Forming Control Method

The progression of the energy transition causes an increasing penetration of converter-based grid components, resulting in a change of the overall grid characteristics. Because the behavior of grid-connected converters is essentially specified by the implemented control, the requirements on these control algorithms increase. Besides the consideration of the fundamental system stability, the maintenance of the voltage quality in future distribution grids becomes an important issue. This contribution presents the concept of a transformer coupled medium voltage converter as STATCOM with energy storage. Based on this topology, damping of harmonic and subharmonic distortions in the grid is improved which results from a voltage source behavior regarding the fundamental grid voltage as well as a current source behavior for harmonic currents of the subordinated grid.