Effects of decreasing synchronous inertia on power system dynamics-Overview of recent experiences and marketisation of services

Decrease of rotational mass in modern power systems is a common experience of system operators around the world. The increasing penetration of variable renewable energy production and thus the use of power converters are fundamentally changing the dynamic behaviour of the power system. The aim of the present paper is to provide an overview on the latest advancements of system operators regarding the analysis and mitigation of the reducing inertia. The theoretical background of power system stability and the calculation of the rate of frequency change are introduced to highlight the importance and the weaknesses of certain metrics used by system operators. Specific operational experiences are compared based on peak load and the nature of the systems. Possible responses by system operators which are discussed in the paper include synchronous and synthetic (emulated) inertia, other technical alternatives (virtual synchronous machines, adaptive load-shedding schemes), and market-based solutions. Besides summarising the advantages and disadvantages of those, grey areas of regulation and market structure are highlighted to facilitate forward-thinking.