| Abstract [eng] |
As synchronous generation is gradually phased out and replaced by renewable energy sources (RES), the electricity system loses its inertia and resilience. Therefore, Grid-Forming (GFM) inverters are becoming a key technology to control the voltage and frequency of the grid and to provide inertia to the system. In this work, control algorithms for GFM inverters are investigated for the integration of RES into the power system. A GFM inverter model has been built in Matlab / Simulink environment, implementing three control strategies: droop, virtual synchronous machine (VSM) and synchronverter. The model was used to perform analyses of the optimal LC filter selection, model stability, short circuit resilience, inertia coefficient sensitivity and islanding mode. The study found that the optimal LC filter size for this model is L = 0.,2 mH, C = 800 µF, R = 0,097 Ω, after applying frequency analysis. The stability analysis showed that the stability of the GFM depends on the grid power and the static coefficient or damping coefficient of the active power control loop. The sensitivity analysis of the inertia coefficient showed that increasing the inertia constant decreases the amplitude of the peak overshoot and the Rate of Change of Frequency, but increases the transient time. Short-circuit and islanding tests showed that all three control strategies remain stable; however, the VSM displays the largest active-power overshoot yet settles in the shortest time. The results show that a properly selected LC filter and control parameters allow GFM converters to reliably maintain grid stability even at high RES levels. |
