环形电流限幅下构网型变流器并网暂态同步稳定性分析OA

The transient synchronization characteristics of grid-forming converters with grid connection are significantly affected by the current limiting unit.Unlike single-axis(d-axis or q-axis)current limiting,the circular current limiting is able to balance both active and reactive power regulation demands,making it a critical type in the engineering design.However,the transient synchronization stability characteristics of grid-connected devices under its influence are still unclear.First,this paper studies the influence mechanism of circular current limiting on the transient synchronization of grid-forming converters with grid connection based on virtual synchronous generator control.It is demonstrated that during the circular current limiting period,there is a jump between the virtual power angle of the converter and the angle of its internal potential and the grid voltage phasor,resulting in the converter exhibiting time-varying phase characteristics as a current source.Then,a calculation method for critical clearing angle considering damping terms is proposed,and the transient synchronization stability characteristics of grid-forming converters with grid connection are further analyzed.It is found that the virtual power angle curves of the converter during the current limiting period are a group of cosine curves with time-varying offsets.Moreover,reduced current limiting thresholds will deteriorate the transient synchronization stability margins of the converters with grid connection.Finally,simulation results validate the correctness of the theoretical analysis.