Power electronic converters as source of virtual inertia for future power grids

Abstract

The increased inverter-based generation and the growing penetration of renewable energy sources into modern power grids have significantly reduced the natural inertia of the system, making frequency stability a critical challenge. This thesis investigates two control methodologies for frequency support in low-inertia grids: inverter-based virtual inertia and reserve-based virtual inertia. The grid-connected synchronous generator was modeled in MATLAB Simulink to represent the core of the power system, and an additional current injection unit was developed to represent renewable sources of solar, BESS, etc. A dedicated control unit was designed in accordance with Fingrid specifications to emulate virtual inertia and deliver structured frequency response using FCR-N, FCR-D and aFRR.

Inverter-based control is a direct approach for stabilizing the system frequency, while the reserve-based approach strictly follows Fingrid specifications and activates a particular reserve based on the frequency band. Each control strategy is simulated under different case scenarios and varied grid-inertia coefficients. The results highlight the strengths and limitations of each individual control method, emphasizing their roles in enhancing frequency stability in low inertia grids.