Influence of wind plant ancillary frequency control on system small signal stability

Since large-scale wind farms are increasingly connected to modern power grids, the transmission system operators put more requirements as part of the grid codes on the integration of wind farms. System frequency control which is normally provided by conventional synchronous generators becomes a common requirement to wind farms. This ancillary frequency control provided by wind farms could have some influence on the system small signal stability. This paper implements an ancillary frequency control strategy on a direct-drive-full-convertor-based wind farm and studies its influence on the damping ratio values of the dominant oscillation modes within the connected power system. All the calculations and simulations are conducted in DIgSILENT PowerFactory 14.0.