Evaluation and Optimization Schemes of Eddy Current Loss on Structural Components for High Voltage Converter Transformer

Compared with the traditional alternating current (AC) transmission system, High-voltage direct current (HVDC) transmission technology plays an essential role in the long distance, large capacity, and regional power grid interconnection, for its characteristics of higher economy, reliability, and stability. As the key power equipment in the HVDC transmission system, the converter trans-former cooperates with the converter valve to achieve AC and DC conversion. Due to the large capacity, high impedance, harmonics, DC bias, and other working conditions for the converter transformer, the eddy current loss of the structural components induced by leakage magnetic flux, will be increased significantly and result in the efficiency reduction and local overheating problem, endangering the operational reliability of itself and the power system. In a flexible HVDC transmission system, regarding the convert-er transformer as the research object, the optimal composite shielding scheme is proposed and determined by the optimization design and finite element analysis (FEA) calculation, which are based on the values and distribution of leakage flux and loss density. Furthermore, the experimental results verify the proposed overall leakage magnetic flux control scheme.