  Large-scale deployment of RES has led to significant generation shares of
variable RES in power systems worldwide. RES units, notably inverter-connected
wind turbines and PV that as such do not provide rotational inertia, are
effectively displacing conventional generators and their rotating machinery.
The traditional assumption that grid inertia is sufficiently high with only
small variations over time is thus not valid for power systems with high RES
shares. This has implications for frequency dynamics and power system stability
and operation. Frequency dynamics are faster in power systems with low
rotational inertia, making frequency control and power system operation more
challenging. This paper investigates the impact of low rotational inertia on
power system stability and operation, contributes new analysis insights and
offers mitigation options for low inertia impacts.
