Mechanism and Control Analysis of Synchronous Frequency Resonance in Distributed Power Generation System Connected to Grid

ABSTRACT The virtual synchronous generator (VSG) control strategy is widely adopted for grid‐connected converters to ensure the stable and grid‐friendly operation of distributed power generation systems (DPGS). However, the voltage sag fault and imbalance DC components fault will cause the synchronous frequency resonance (SFR) phenomenon, which will pose a serious threat to the stability and power quality of GC‐DPGS. Furthermore, its underlying mechanisms and effective suppression methods remain inadequately explored. The paper employs a small‐signal analysis, first establishing a small‐signal model for the GC‐DPGS and then deriving the transfer function between grid disturbances and output power by combining the VSG controller model. Under the premise of considering power coupling, the mechanism of SFR is discussed in detail by using the above small signal models. The fundamental reason is identified as insufficient system damping, which places the transfer function's poles near the imaginary axis and enables the DPGS to amplify synchronous frequency signals from external faults. To suppress the SFR, a virtual resistance module is incorporated into the control loops to damp the resonance peak. Finally, hardware‐in‐the‐loop experiments validate the SFR analysis and confirm the effectiveness of the proposed suppression strategy.