Abstract: Wind farm is rapidly increasing across the world as a cheaper source of green energy and as fossil fuel is depleting every day. Most conventional power plants have being replaced by wind turbines generators as a result of the high increasing penetration of renewable energy especially wind power, but this has negatively impacted on the frequency stability and reliability of 2 due to wind speed variability. A required frequency can’t be compromised, so a new global grid code regulation mandates all wind turbine generators (WTGs) in an interconnected electricity network to participate in primary frequency control (PFC) for the curtailment of frequency disturbance in the power system as a result of generation and consumption imbalance. Evidence shows that the deloaded mode of operation which makes the wind turbine participate in the primary frequency control is still emerging and very vast in scope and has a critical role to play as reliability and availability of electric power in this industrial age is concern. This paper provide an extensive up-to-date literature review of deloaded mode of operation for primary frequency regulation in a of wind turbines generators in an interconnected grid system. Various control modes and comparisons with the deloaded mode are highlighted as well. Again, a glance into some factors that determine quantity and quality of the power reserve margins, the percentage of reserve margin per the level of wind farm penetration and some optimization processes as well as projected future research works.