The growing penetration of distributed energy resources (DERs) has increased the complexity of the power system due to their intermittent characteristics and lower inertial response, such as photovoltaic (PV) systems and wind turbines. This restructuring of the power system has a considerable effect on the transient response of the system resulting in inter-area oscillations, less synchronized coupling and power swings. Furthermore, the concept of being distributed itself and generating electricity from multiple locations in the power system makes the transient impact of DERs even worse by raising issues such as reverse power flows. This paper studies some impacts of the changing nature of power system which are limiting the large scale integration of DERs. In addition, a solution to increase the inertial response of the system is addressed by adding virtual inertia to the inverter based DERs in the power system. The proposed control results in increasing the stability margin and tracking the rated frequency of the system. The injected synchronized active power to the system will prevent the protection relays from tripping by improving the rate of change of frequency. The proposed system operation is implemented on a sample power grid comprising of generation, transmission and distribution and results are verified experimentally through the Opal-RT real-time simulation system.