Large-disturbance stability analysis method based on mixed potential function for AC/DC hybrid distribution network with PET

The dynamics of the power electronic transformers (PETs) have brought great challenges to stability analysis of the AC/DC hybrid distribution network with PETs. In this study, a large disturbance stability analysis method is proposed for the AC/DC hybrid distribution network with PETs, based on the mixed potential function (MPF) theory. Firstly, the simple average models of the converters based on the controlled sources with the control links are presented to describe the dynamic characteristics of the AC/DC system, which are suitable for the MPF theory. Subsequently, the method of constructing the MPF for the non-linear links in PET is proposed to derive a stability criterion for the AC/DC hybrid distribution network. The effects of the AC and DC dynamic characteristics and the non-linear control links are both included in the criterion. Multiple scenarios of the faults or the large disturbances are used to investigate the effect of the stability criterion, and the results show that the stability state of the multi-PET distribution network could be reflected by the stability criterion under various large disturbances. Finally, the parameter-influence analysis method is proposed to improve the stability of the system.