Modeling and Stability Analysis of a Power Electronic Transformer-based Active Distribution Network

Stability is of great concern for active distribution network that integrated with Power Electronic Transformer (PET). Under this circumstance, this paper gives detailed derivations of the small signal impedance models of PET and grid emulator in the synchronous rotating (dq) frame at first, which is further verified by comparing the calculated impedances with the measured ones in software. Then the impedance-based Nyquist stability criteria is used to determine the stability of the interconnected system. Moreover, two simulation cases both in time domain and frequency domain are given, showing the stable and unstable conditions by adjusting the control parameters (modifying the ratio of the source and load impedances). Finally, the experimental results verify the practicability and validity of the proposed models.