Power system stability enhancement with grid forming controls and process towards grid forming grid code

The electricity system of Finland has faced new challenges due to the increasing penetration of inverter-based resources (IBR), such as wind power. Rapid increase of IBR can cause new stability challenges such as converter driven and resonance stability issues. Fingrid, the Finnish transmission system operator, has implemented various measures to mitigate these issues. These measures include new monitoring tools, technical requirements, operational guidelines and tendering grid supporting devices. This paper presents large-scale electromagnetic transient (EMT) simulations that compared the performance of different grid supporting devices, such as synchronous condensers, grid following (GFL) and grid forming (GFM) static synchronous compensators (STATCOMs), and GFM battery energy storage systems (BESSs). The results highlight the effectiveness of GFM based devices to improve the damping of converter-driven and resonance oscillations. Fingrid has decided to invest in a synchronous condenser and GFM STATCOMs, and to require GFM control for new BESS connections in regions with high converter penetration. The paper also presents the new Finnish grid forming BESS requirements and discusses future challenges and opportunities of hybrid power plants and converter-connected loads.