Operation of large power systems with small amounts of physical inertia
The project has treated the experienced problems of the current instability in the railway power grid (also called the electrified traction grid). As the railway electricity network in Sweden has been expanded with an increased proportion of static converters has the proportion of physical inertia of the system been reduced. Generally, the network has been changed in terms of its characteristics particularly in regards of transients.
Sponsor: Energimyndigheten, Trafikverket
Researcher: Math Bollen, Martin Lundmark, Lars Abrahamsson
Duration: 2017
The project has treated the experienced problems of the current instability in the railway power grid (also called the electrified traction grid). As the railway electricity network in Sweden has been expanded with an increased proportion of static converters has the proportion of physical inertia of the system been reduced. Generally, the network has been changed in terms of its characteristics particularly in regards of transients.
A number of events in both southern Sweden and events related to the high-voltage transmission system extending between Svealand and Upper Norrland motivated project.
If the power supply to the railways suffer from instability and, at worst, longer interruptions it will naturally affect the traffic. This may affect the willingness to use the railway, which is an energy efficient mean of transportation that can be supplied with electricity produced from renewable energy sources.
The project has studied literature and data. Models have been developed and adapted to the software used. Software was selected based on what best suits the desired models.
Simulations have been made with two main purposes. One is that, by comparison with the measured data, to verify that the models and the software provides realistic descriptions of the railway power grid during transients. The second is to vary problem setups, network configurations and events to build a deeper and broader understanding of how the system generally behaves.
The project has increased the understanding of the system structure and the demands on modeling for the simulations to reproduce the experienced problems. This has been done in order to later find ways to avoid these problems. Through model-development and simulations, particularly new insights have been gained regarding the interactions between the static and the rotary converters for various electrical distances between them in the railway power grid during transients.