Relationship between power system inertia and inter-area mode natural frequency – Analysis and measurements

Due to the introduction of wind and solar power into power systems, there has been a growing interest in power system inertia during previous years. Also, in several power systems, monitoring of both the frequencies and damping of electromechanical inter-area oscillations has become of interest as these oscillations may challenge power system stability and limit transmission capacity. This paper presents the theoretical relationship of inertia and inter-area mode natural frequency and demonstrates with measurements from the Nordic power system that this relation can be observed also in a real power system. This finding is useful for continuous inertia evaluation based on estimation of inter-area mode natural frequencies and may be used to evaluate other dynamic properties of the power system as well. • Derivation of a relation between an inter-area oscillation mode and kinetic energy. • Validation of the relation with real measurements from the Nordic power system. • Discussion on how this relation can be used in analysis of power systems.