As the percentage of wind energy in global energy portfolio rises, the wind turbine control is becoming increasingly important for the integration of wind turbines in power systems. The early control objective of wind turbine control was only to maximize the power output but now the wind turbines are required to provide frequency control as well. To emulate the inertia response (IR) of the conventional synchronous machines the wind turbines can be provided with an inertia emulation controller. The modelling work presented in this thesis aims at equipping the modern Type D wind turbine with inertia response and primary frequency control capabilities. Two controllers — inertial and droop, are implemented and their frequency control capabilities are compared in an isolated power system consisting of a conventional steam turbine generator and a wind farm. A model of one Type D wind turbine is simulated and aggregated for the whole wind farm. The ability of wind turbines to provide inertial response (IR) and primary frequency control (PFC) after a frequency deviation shows a better performance than the case when there is no contribution to frequency control through wind turbines.