The influence of inrush current of converter transformer on HVDC and key equipment

This study focuses on the influence of converter transformer inrush current in HVDC transmission system. In order to quantify its impact on system operation, a UHVDC simulation model is established to study the generation and transmission characteristics of inrush current. The measuring points are set at the AC and DC side. The excitation inrush current is analyzed by FFT. The main harmonics flowing into the AC side are significantly weakened by the filter, but there are still residual harmonic components. After filtering, the DC side current sudden change and low-order harmonics still remain. This shows that the power quality of AC and DC side is affected by inrush current. Through the relationship between temperature and insulation life, the aging of insulation life of converter transformer is evaluated. Markov state space model is used to quantify the impact of inrush current on the available transmission capacity of the system. The research shows that inrush current leads to the decline of DC power quality, the decline of transmission capacity and the acceleration of insulation aging.