With the deepening of power electronicization in power system

grid-forming converters with voltage source characteristics will become conventional equipment in modern power systems. In order to conduct accurate and efficient control and operation analysis for power systems equipped with grid-forming equipment and to study their safety and stability characteristics

it is necessary to reduce the complexity of grid-forming converter model with strong nonlinear characteristics. Conventional simplification methods based on current loops and voltage control loops neglect the potential effect of inner loop control and line coupling impedance on the synchronous stability of the equipment. Ensuring the accuracy of stability analysis can be challenging in certain scenarios.Therefore

based on the existing order reduction methods

fully considering the small-signal characteristics of inner loop control and the influence of line coupling impedance

a series of improved simplified models are proposed. Moreover

the adaptability of each simplified model to frequency domain

eigenvalues

and time domain analysis is discussed. It turns out that there is no simplified model that can always maintain high accuracy in all scenarios. It is concluded that the simplification method needs to be changed according to the scenario.According to the analysis results

the relevant basis for selecting the simplified model of the converter and adjusting the control parameters is summarized.