Research On DC Bias Reactive Power Loss Model Of 800 KV Converter Transformer Based On Finite Element Method

Converter transformer is the most important power equipment in UHVDC transmission.DC bias phenomenon will lead to more reactive power demand of converter transformer,which poses a threat to the safe operation of converter transformer and power grid.In order to grasp the variation law of DC bias reactive power loss of converter transformer,a calculation model of reactive power loss for 800 kV single-phase dual-winding converter transformer is proposed in this paper.The main work is as follows:Firstly,according to the generation principle and influencing factors of reactive power loss under DC bias of transformer,the principle and calculation process of J-A theory’s hysteresis model,field-circuit coupling model and magnetic-circuit coupling model are summarized.The engineering algorithms of transformer reactive power loss based on K value method and U-1 curve are compared and studied.Secondly,according to the structure parameters and core parameters of converter transformer,using Ansoft Maxwell finite element platform,a three-dimensional finite element model of 800kV single-phase dual-winding converter transformer is established and a DC bias reactive power loss algorithm for converter transformer is proposed.Finally,the deterministic relationship between the reactive power loss and the bias DC of converter DC is obtained by combining the reactive power calculation method.Using the finite element model of converter DC,the peak excitation current of converter DC bias under different short-circuit impedance is simulated,and the variation law of the reactive power loss of converter transformer under different loads under DC bias is studied.The reactive power loss of converter transformers with different voltage levels and different core structures under the same bias current is analyzed.The research results of this paper can provide useful reference for the treatment of DC bias in UHVDC transmission.