A Study of Power-Frequency Dynamics in Isolated Power Networks with 100% Converter-Interfaced Generation

The operation of a system with 100% converter-interfaced generation poses several questions and challenges regarding various aspects of the dynamic characteristics of the system. The effects related to the power-frequency control are among the most relevant issues which need to be investigated. The paper takes into examination the case of an existing isolated power network of a geographical island assuming a completely converter-interfaced generation. The factors playing a fundamental role in the assessment of which sources should be designated to be grid-forming are identified with a small signal model formulation of a generic multiple oscillators system. Simulations and analysis performed on the case study of the island’s power network performed with the software NEPLAN are used to show the impact of different aspects which can play a role in the design and the operation of the system: these aspects are the operating mode of power converters control, location and distribution of the generation sources with grid-forming capabilities, as well as number and ratings of these sources. The impact of relevant control parameters such as virtual inertia constant and virtual impedance is also investigated.