Modeling for Analyzing Practical Oscillation Event of AC/DC Distribution Networks with Power Electronic Transformer

In an AC/DC distribution network test of an integrated energy service center in Jiangsu Province, it is found that there is an oscillation phenomenon on the DC side with unclear mechanisms. In order to analyze the practical oscillation phenomenon, this paper proposes detailed models of the AC/DC distribution network, which considers a power electronic transformer (PET), two three-phase voltage-source converters (VSCs), and a buck converter. First, the basic structure and simplified model of the AC/DC distribution network are introduced according to the practical power grid. Then, the topological structure and control method of each equipment is presented in detail, so as to establish the mathematical model of each equipment and the whole AC/DC distribution system. Finally, a simulation model is built on the MATLAB platform to reproduce the oscillation event and further qualitatively analyze the factors affecting the oscillation. These qualitative analysis results provide reasonable suggestions for system operators to ensure the safe and stable operation of AC/DC distribution networks. Moreover, the practical oscillation occurred at AC/DC distribution networks is little reported previously, and thus the practical recording data and detailed models of the AC/DC distribution networks provided in this paper are valuable for academic researchers to in-depth study the oscillation mechanism.