Shaping the Transient Performance of Droop-Controlled Grid Forming Converters for Frequency Regulation

This paper proposes an effective method to improve the transient performance of droop-controlled grid-forming (GFM) inverters for frequency regulation. The active power droop control is an industry-accepted method for primary frequency control and performs well with the large and slow synchronous machines with large inertia. Unsatisfactory transient performance has been observed, however, for the small and fast converter-based generators as the droop control is fundamentally based on a steady-state model. This paper thus presents a method to shape the desired transient response by augmenting the standard frequency command with an additional command through a fast frequency regulation responding to the change in the inverter's DC voltage. The method is practical as it exploits the measurements only, not requiring the modification of DC voltage control unlike the recently developed matching scheme. Case studies using PSCAD/EMTDC highlight that the proposed method significantly improves the transient performance while providing the desired load-sharing in steady-state.