多环路构网型变换器的串并联序阻抗模型

The gradual penetration of grid-forming(GFM)converters into new power systems with renewable energy sources may result in the emergence of small-signal instability issues.These issues can be elucidated using sequence impedance models,which offer a more tangible and meaningful interpreta-tion than dq-domain impedance models and state-space models.However,existing research has primarily focused on the impact of power loops and inner control loops in GFM converters,which has not yet elucidated the precise physical interpretation of inner voltage and current loops of GFM converters in cir-cuits.This paper derives series-parallel sequence impedance models of multi-loop GFM converters,demonstrating that the voltage loop can be regarded as a parallel impedance and the current loop as a series impedance.Consequently,the corre-sponding small-signal stability characteristics can be identified through Bode diagrams of sequence impedances or by examin-ing the physical meanings of impedances in series and in paral-lel.The results indicate that the GFM converter with a single power loop is a candidate suitable for application in new power systems,given its reduced number of control parameters and enhanced low-frequency performance,particularly in weak grids.The results of PLECS simulations and corresponding pro-totype experiments verify the accuracy of the analytical analysis under diverse grid conditions.