An Assessment of Costs for System Inertia in Future Power Systems consisting of a high Share of Non-Synchronous Penetration

The need to limit global warming by decarbonising power systems drives the replacement of fossil fuel-fired power plants with renewable energy sources. For the most part, with frequency converter connected wind turbines and photovoltaic systems. As a result, power system inertia decreases. To maintain the controllability of the grid frequency, countermeasures need to be taken, which are associated with costs. This work assesses costs for system inertia in future power systems with a high share of non-synchronous penetration. Publications part of this cumulative thesis are categorised into three phases. The first phase assesses the basics of system inertia and defines fundamental assumptions. In the second phase, single topics such as load inertia, inertia provision via the day-ahead market and the influence of synthetic inertia provided by wind turbines on the power system are assessed. The last phase combines previous findings and analyses system costs of the future German power system due to the provision of inertia. In the Continental European power system, non-synchronous flywheel systems are the least-cost solution to provide necessary synthetic inertia with total annual costs of 167.64e/(kg·m2). Currently, load inertia accounts for 20% of the total system inertia and contribution of different consumer groups varies significantly. Securing sufficient system inertia in the Irish power system via the day-ahead market results in additional operating costs ranging from 1.02e/(kg·m2) to 4.49e/(kg·m2). Wind turbines can provide continuous inertia and are thus able to reduce must-run capacities and resulting CO2 emissions in the Irish power system by 31 %, curtailment by 40% and system costs by 33 %. Results indicate costs in future German power systems for inertia provision in the range from 0.002e/(kg·m2) to 0.61e/(kg·m2). Wind turbines and synchronous condensers equipped with flywheels providing inertia are the most cost-efficient solution to maintain the controllability of the grid frequency in future power systems. Higher CO2 certificate prices need to be taken into account to achieve overall decarbonisation targets. Further, reduction of primary power reserves activation time is crucial.