Modeling and simulation of magnetizing inrush current of the VSC-HVDC converter station multi-legged transformer

This paper proposes an electromagnetic transient model of the voltage source converter (VSC) based HVDC transmission converter station multi-legged transformer. Currently, three phase multi-legged converter transformers are often used in VSC-HVDC schemes. However, VSC-HVDC converter transformers are normally represented as magnetically and electrically independent single phase units when simulating the transformer electromagnetic transient. Therefore, the duality derived magnetizing inrush model, which considering electric circuit coupled with magnetic circuit, is developed from the structural parameters of the multi-legged converter transformer. In the analysis of the magnetization curve, the relationship between the magnetic field intensity and magnetic flux density differs from the ordinary B-H curve. It is defined on the basis of Jiles-Atherton ferromagnetic hysteresis theory in this paper. Moreover, the new model can evaluate the magnetizing inrush current of converter transformer in transient state, and it can provide the VSC-HVDC system with a more thorough transient analysis. Experiments and simulation results are carried out to verify the proposed model.