In order to accurately and quickly perform electromagnetic transient simulation of single-phase four-leg converter transformers

this paper proposes a single-phase four-limb converter transformer saturation model based on no-load test data and UMEC（unified magnetic equivalent circuit） model. Based on the UMEC magnetic circuit model

the method of solving the incidence matrix

inductance matrix and core permeance of the single-phase four-limb converter transformer is derived. When considering the saturation of the core

the excitation branch is simulated by the parallel connection of a nonlinear resistance and a nonlinear inductance. Through the no-load test data

the piecewise linearization curves of u–i R and u–i L in the excitation branch are obtained to simulate the core loss and the nonlinearity of the magnetic permeability.The method in this paper is based on the UMEC model

meanwhile

the nonlinearity of the core main column

iron yoke

side column and side yoke magnetic guide as a whole is taken into account

thus the method has the advantages of fast calculation speed

high efficiency and high precision. Finally

the method in this paper is used to simulate and calculate the scaled model and the product-level single-phase four-limb converter transformer under normal operating conditions and DC bias conditions. The comparison with experimental measurements proves that the model has high accuracy.