Fast DC Bias Calculation for UHV Transformer on Load

With the large-scale construction of UHVDC power grid in China, the importance of UHV transformer in power system is increasing. High voltage direct current (HVDC) and geomagnetic storms cause DC bias of transformer, thus affecting the reliability of power supply. Aiming at the low efficiency of DC bias calculation for UHV transformer, starting from the characteristics of the field-circuit coupled principle, the two-dimensional simulation model of UHV transformer is established to improve the solving speed of magnetic field, and the correctness of the model is verified. Based on the two-dimensional magnetic field model, the computational workload of the circuit model is further reduced by applying a variable step strategy. The results show that the calculation method can complete the DC bias calculation of UHV transformer on load in a short time, and the calculation accuracy can be guaranteed, so as to predict the safe and stable operation of power system.