Frequency response enhancement of an AC micro-grid has renewable energy resources based generators using inertia controller

•Inertia controller to improve the frequency response of AC micro-grid is proposed.•The controller is applied on micro-grids with high penetration of wind generation.•The response is analyzed at load change, wind speed variation, and short circuit.•The relation of the proposed controller and microgrid inertia is proved.•The amount of inject power/energy with frequency deviation is proved and discussed. Since low inertia has drawbacks on the frequency response and stability of AC micro-grids, availability of sufficient inertia with high penetration of renewable energy sources, has recently become a topic of wide concern. To tackle the problems of low inertia operation, most research is focused on using of an energy storage system (ESS) or de-loading of the renewable generation units. However, these techniques have economic problems due to investment in extra elements or reduction of the system productivity. A new inertia controller that depends on the inherent system's elements, such as the kinetic energy stored in wind turbine and the high bandwidth of interface converter, is proposed. The controller is applied on an AC micro-grid consisting of a thermal power plant and a doubly-fed induction generator based wind turbine. To ensure the validity of the proposed technique, different simulation cases such as load disturbance, wind speed variation, and three-phase fault are performed using MATLAB/ Simulink platform. The results are compared with the responses of two other AC micro-grids operate under the same conditions. The suggested controller successfully enhances the micro-grid frequency response with less frequency nadir and less rate of change of frequency. Eventually, the mathematical description of the proposed controller effect on the inertia of the WECS and the inertia of the micro-grid is deduced.