接入大电网的定频构网与虚拟同步机控制同步稳定性比较研究OA

Frequency-fixed grid-forming(FF-GFM)control is a novel grid-forming control architecture.In future power systems dominated by converter-interfaced generation(CIG),CIG can operate as a constant-frequency,constant-voltage source within its capacity,significantly reducing system frequency and synchronous dynamics and fundamentally resolving synchronization instability issues.In this paper,it is found that when the proportion of FF-GFM CIG is low and insufficient to dominate the system dynamics,the system may struggle to achieve global fixed-frequency characteristics;however,FF-GFM can still play a positive role in grid support and offers notable advantages over virtual synchronous generator(VSG)control.Specifically,FF-GFM can be implemented simply on an existing GFM converter with VSG control by introducing an intentional deadband in the power.Then,using the describing function method,we proved that adding a deadband can improve the damping ratio of low-frequency oscillations.Moreover,by analyzing the stability region and system trajectory during and after the fault,it can be shown that FF-GFM enhances large-disturbance synchronization stability and effectively increases the fault-clearing time.Finally,the conclusions are verified with Hardware-in-the-loop simulations.These findings indicate that FF-GFM is highly compatible with existing VSG control in implementation and can effectively enhance synchronization stability,even during the transitional stage of low-penetration integration,thereby supporting the gradual transition of the power system.