Solutions to Improve Transient Stability of Universal Grid-forming Inverter-based Resources

In the future power grids, the share of grid-forming inverter-based resources must be increased in order to guarantee stability of the power system during rapid changes in generation, consumption and network topology. Therefore, it is important that the behavior and response of grid-forming inverters is also stable during different types of operation modes, events and faults. Previously, frequency stability improvement of grid-forming battery energy storages with universal frequency-locked-loop after load change in small HV network has been studied. However, in this paper the focus is on more severe disturbances i.e. unbalanced 2-phase and balanced 3-phase faults that are typically most challenging for the different synchronization methods. In this paper, based on multiple PSCAD simulations, new solutions are proposed to improve the transient frequency and voltage stability and fault-ride-through capability of grid-forming inverter-based resources with universal frequency-locked-loop during and after unbalanced and balanced faults.