Calculation And Analysis Of Harmonic Loss And Thermal Problems On Converter Transformer

The calculation and analysis of harmonic loss and thermal problems on converter transformer is the key issues in the process of converter transformer design and optimization. To use of filters can reduce the impact of harmonics on the system, but can't completely eliminate the internal winding harmonics of converter transformer, these high harmonic currents in the converter transformer generated internal harmonic leakage field, and generated harmonic losses in the windings and metal structures, as the same time some of the metal structure may lead to a partial overheating, therefore, it is great significant that deeply and accurate study harmonic losses and thermal problem to design and development of converter transformer.In this paper, domestic and international general research situation on harmonic losses and thermal issues of HVDC are discussed. To make a ZZDFPZ-297.6MVA/500kV converter transformer as research object, and reasonable simplified its complex model, then the harmonic losses and thermal issues has been calculated and analyzed according to this model by applying theory of power transformer electromagnetic fields and finite element analysis, and the relevant of hydromechanics and heat transfer theory. First, the leakage fields and short circuit impedance in two large power transformers were calculated and the results are consistent with the experimental data. An engineering algorithm to analyze leakage magnetic field in converter transformer bases on MagNet software is concluded by calculation of TEAM Problem 21 A and B model. Secondly, leakage magnetic field and harmonic loss in the converter transformer has been accurately calculated by making its leakage computation model. Then the distributions of leakage magnetic field in converter transformer, the short-circuit impedance, the harmonic loss of different tap windings and the stray loss of structure have been obtained, and the method to reduce harmonic loss has been given. Finally, by using the theory of fluid dynamics and computation heat transfer and the principle of power transformer heating and cooling, the thermal computation model of converter transformer has been established by using FLUENT software. The distributions of oil flow field in converter transformer and temperature field of winding have been given by simulation computation, the method to reasonable control oil flow and reduce the temperature have been proposed.In this paper, the method of reduce harmonic losses and reasonable controlling temperature of converter transformer has been given by calculation and analysis of harmonic loss and thermal problem on converter transformer, the effeteness of calculation and analysis method are validated, which has guidance significance to rational design and performance optimization of converter transformer.