Impact of Transformer Flux Saturation on Tranisent Overvoltage Analysis of Sending-End Power Grid with Wind Farms

This paper analyzes the impact of transformer saturation on sending-end power system transient overvoltage caused by the high-voltage direct current (HVDC) transmission system commutation failure. It illustrats that transformers absorbs reactive power when entering the saturation state, which will affect overvoltage assesment and control of sending-end power grdi. First, it analyzes the transformer magnetic saturation impact on transient overvoltage results of sending-end power grid. Second, it introduces the electromagnetic transient simulation model of the transformer with magnetic saturation. Then, it demonstrates that the saturated transformer will absorb reactive power when overvoltage occurs, and derives the relationship between the reactive power absorption and the overvoltage. Next, a correction method for overvoltage simulation results that do not consider transformer saturation is proposed. Finally, the correctness and feasibility of the theory analyses and correction method proposed in this paper are verified through two different test systems with different scales.