Modelling, Simulation, and Validation Tests for Sub-harmonics Protection Relay

The participation of renewable power plants including wind, solar, inverter, battery energy storage systems, and hybrid power plants is growing drastically in Finnish power grid. This shift has introduced new challenges to the power system stability and dynamics such as subsynchronous oscillations (SSO), which are defined as high-amplitude undamped oscillations at frequency range 5-45 Hz. Especially, with the growing number of doubly fed induction generator (DFIG) wind power plants, a new form of SSO interaction has emerged, i.e. sub synchronous control interaction (SSCI). The SSCI may potentially appear because of the subsynchronous interaction between wind power plants and series compensation capacitors. To avoid the equipment failure in the occurrence of SSCI, sub-harmonics protection…