Impact of GFM Control on Sub-Synchronous Oscillation in New Energy Stations

Long-distance integration of grid-following(GFL) renewable energy power stations into low short-circuit ratio grids is prone to induce subsynchronous oscillations(SSOs), thereby limiting their power transmission capacity. Conversely, grid-forming(GFM) renewable energy sources demonstrate robust performance in weak grid conditions and are pivotal in enhancing the short-circuit capacity of renewable energy stations to uphold stable operation of weak grid systems. This paper delves into the impact of GFM integration on the SSO stability of GFL stations. It establishes a small-signal equivalent impedance model for hybrid stations that incorporate both GFL and GFM converters, proposes stability criteria for grid-connected hybrid renewable energy stations, and analyzes the influence of GFM control on the SSO characteristics of these stations through time-domain simulations. The findings reveal that parallel connection of GFM converters at the point of common coupling(PCC) can effectively mitigate the risk of SSOs in sending-end stations operating under low short-circuit ratios(SCRs) conditions, thereby augmenting their power transmission capability.