With wind penetration levels increasing in power systems across the world, different challenges are encountered with respect to the controllability and operation of a power system. One main concern is the fact that the frequency regulation of a power grid is highly impacted when a considerable amount of electronically decoupled systems, such as wind energy, is connected to the system. This paper uses a dynamic, non-linearized system developed in Matlab/Simulink©, to study how Type-3 (DFIG) wind turbines impact the stability and frequency response of a test power system. Operating the wind turbine in a de-loaded mode by intentionally spilling power to provide additional power headroom is one solution to this problem. In this work a proposed frequency sensitive pitch angle controller is implemented and tuned by a Genetic Algorithm. A phasor model is used for the wind turbine to study the longer timescales associated with the primary frequency response regime. Time simulations are used to demonstrate the transient and steady-state performance of the proposed controllers in the test system with 25% wind penetration. The results show that the addition of the tuned frequency sensitive controllers improved the settling frequency, rate of change of frequency, and frequency nadir compared to the wind turbines without these controllers.