提升混合同步控制型虚拟同步发电机系统的同步能力

The hybrid synchronization control (HSC) technique, which combines power-based synchronization of virtual synchronous generators (VSGs) with phase-locked loops (PLLs), has gained significant interest due to its dynamic capabilities. However, its small-signal properties, e.g., stability region, virtual inertia, and damping performance, have not been fully investigated. This article therefore addresses this gap by analyzing the HSC-based VSG system from an impedance perspective, considering the coupling between the power loop and inner control loops. The study shows that HSC induces non-passive regions in the VSG’s impedance in the qq channel, which can destabilize weak grids. Increasing the PLL bandwidth can also reduce the system’s equivalent inertia and damping. In response to these issues, an improved HSC technique is proposed by incorporating a coupling-weakening function and a hybrid-frequency feedforward control. The improved HSC mitigates the instability caused by the impedance intersection and enhances the provision of virtual inertia and damping compared to existing HSC. This results to a lower rate of change of frequency, and a higher frequency nadir. Finally, experiment was carried out to verify the theoretical capabilities of the proposed scheme.