The mathematical model of the new converter transformer based on modified node method

Compared with the traditional converter transformer, the auto-compensation and harmonic shielding converter transformer, namely, the new converter transformer, has a unique connection. In general, the difficult branches that only contain solitary voltage source sometimes appears in the mathematical modeling for the transformer, but the traditional nodal equations of the transformer are unable to be established due to the absence of the branch admittance matrix. Based on the coupled circuit principle and the actual design parameter of the new converter transformer, the three-phase basic mathematical model is presented according to the modified nodal method combined with the directed graph of the coupled circuit. Finally, the simulation results demonstrate that the mathematical model established by the modified nodal method is accurate and effective. The proposed method can be selected flexibly in practical project and has universal significance in solving various actual engineering problems correlated with multi-transformers.