The integration of large number of renewable energy resources based on converter interfaces led to frequency stability issues in power systems. Virtual inertia and primary frequency control strategy of the renewable energy units can enhance their active frequency support capability

but their control performances may not fulfill the requirement. Accurate estimation of the frequency control capability of renewable energy units based on measurement is crucial for ensuring the frequency stability of low inertia power systems. The existing evaluation methods fall short of accurately accounting for two critical factors: the dynamic processes of renewable energy resources following system perturbations

and the inherent coupling between inertial characteristics and primary frequency control power. These oversights might introduce significant deviations in estimation outcomes. This paper first compares the dynamic frequency response between synchronous generator and renewable generators

and then proposes a method to decouple the inertia control power and a parameter identification method to estimate the inertia constant based on the decoupled inertia power. Finally

a hardware-in- the-loop experimental platform for estimating the frequency control capability of renewable energy resources is constructed using the real time digital simulation system and phasor measurement unit. The evaluation results of virtual inertia time constant and primary frequency control coefficient are validated with the test platform and field data. The result shows accurate frequency control capability can be obtained with the proposed methods

which will be helpful for the capability configuration and parameter setting of the frequency control resources.