Abstract
To investigate the stray loss in magnetic shielding components immersed in the 3-D AC-DC hybrid leakage magnetic field, a modified method is presented with the variation of the eddy current loss inside the coil due to the change of the leakage magnetic field taken into account. In addition, a new loss separation model is proposed to estimate the standard iron loss of the grain-oriented (GO) silicon steel sheet under AC-DC hybrid excitations. Furthermore, the material properties were appropriately treated based on the simplified model of laminated magnetic shielding for efficient numerical calculation. The comparison of field distribution and loss results obtained by experiment and calculation respectively was made, which shows good consistency and thus verifies the effectiveness of the proposed method in this paper. Meanwhile, the stray loss and additional loss in magnetic shielding are analyzed in detail to evaluate the potential threat of AC-DC hybrid excitations on the local overheating of the structural parts in HVDC transformers.
Highlights
With the rapid development and widespread application of the HVDC transmission system, as a critical equipment of the system, the converter transformer has gained more and more concerns in recent years
As far as the DC bias are concerned, the main causes are as follows: (1) Geomagnetically induced currents (GICs) in transmission lines caused by magnetic storm; (2) Earth return currents (ERCs) during monopolar operation of HVDC transmission, etc [5]-[6]
In HVDC transmission, the DC magnetic field in iron cores and magnetic components can be generated in different ways
Summary
With the rapid development and widespread application of the HVDC transmission system, as a critical equipment of the system, the converter transformer has gained more and more concerns in recent years. Based on TEAM P21c benchmarking, the leakage magnetic field, stray loss as well as additional loss are computed and analyzed to evaluate the potential impact of AC-DC hybrid excitation on magnetic shielding components in HVDC transformers. STRAY LOSS DETERMINATION BY MODIFIED METHOD when there is magnetic shielding beside the excitation coil, which is called “load condition”, the total loss to be measured experimentally can be denoted as Pload and should include the following three parts, Pload = Pcoil.o + Pcoil.ec + Pt (2). ΔPcoil.ec can be calculated by the following equation based on measured results as well as the precisely estimated loss coefficient, In such way, the stray loss can be determined more reasonably and accurately, Pt = Pload − Pno-load −. As can be seen from the figure, the fitted results by the proposed method show better consistency with experimental ones, especially when Bm is greater than 1.6 T
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