Stability Analysis of Grid-following Converters in Power Systems Depending on Grid Stiffness

The integration of renewable energy sources in power systems has become a stability challenge. Their connection is made via power electronics, mostly using a grid-following control scheme. However, it has been proven that this type of control raises instability problems when they are connected to weak grids. This paper focuses on analyzing the stability of grid following converters when connected to grids with different stiffness using frequency analysis. Firstly, an assessment of the converter’s passivity indicates the frequency range where the grid stability can be compromised. Then, a time-domain simulation shows how the converter responds to a voltage dip in each case. Finally, the frequency-domain impedance on the small-signal model reconfirms the previously obtained results. The conclusions support the theory explained and point possible future applications. Key words. Grid-following converter, weak grid, stability, passivity, impedance stability analysis.