Utilizing Grid Forming Battery Energy Storage to Mitigate Subsynchronous Interaction between Type-4 Wind Turbines and Weak AC Grids

With the significant increase in the proportion of intermittent renewable power generators, there has been an increasing application of grid-scale battery energy storage systems (BESSs) to store excess power. In addition to this, it is of great interest to utilize the BESS as a means to provide a wider range of power grid services. This paper aims at using grid forming (GFM) controlled BESS to suppress synchronous oscillations (SSOs) that may be caused by the interaction between nearby grid following (GFL) controlled type-4 wind farms and weak ac grid. This paper proposes two subsynchronous damping controllers (SSDCs) as modifications to the GFM control structure of the BESS such that the BESS provides positive damping for the unstable SSO modes in the GFL-controlled wind farm. The damping performance of the two SSDCs is compared and the effect of the capacity of the BESS on the damping is investigated. The results are verified through time-domain electromagnetic simulations.