Abstract For the converter transformer, the eddy current loss of the tank under DC bias will increase significantly, which will lead to the temperature rise of the transformer and threaten its safe and stable operation. Therefore, it is necessary to quickly evaluate the eddy current loss of the tank under DC bias. At present, given the particularity of the load current of the converter transformer, much research work has been carried out to study the relationship between the stray losses of the structural components corresponding to different harmonic contents. However, the research conclusions do not consider the impact of DC bias applied to the converter transformer. The research on the stray loss of tanks, pull plates, and other structural parts under DC bias is mainly based on AC transformers. Therefore, considering the characteristics of the nonlinear load current of the converter transformer, this paper analyzes the change of eddy current loss of the tank under DC bias. Firstly, the distribution of the magnetic circuit on the tank surface under different working conditions is analyzed. Combined with the actual nonlinear load current waveform and eddy current loss calculation formula, the influence of converter trigger angle and DC on the tank eddy current loss at the rectifier and inverter sides is obtained. According to the analysis conclusion, a loss ratio factor k is introduced, and a simplified formula for calculating the eddy current loss of the tank when the dc bias is applied is given. Then, the finite element simulation software COMSOL is used to build a finite element model of the eddy current loss of the tank of an 800 kV converter transformer. The field circuit coupling simulation is carried out with the external circuit of the primary and secondary sides of the converter transformer. The converter transformer tank current loss index under rated conditions has a small error compared with the value of the IEC standard, which also proves the correctness of the model to a certain extent. The simulation value variations of tank loss under DC bias, surface magnetic field, and eddy current distribution are also consistent with the theoretical analysis. Finally, two 380V transformers with a 1:10 structure scale are used to verify the theoretical analysis and simulation calculation. The main conclusions of this paper are as follows: (1) When DC bias is applied to the converter transformer, the eddy current loss of the tank can be expressed as the rated loss multiplied by the ratio factor k and the no-load DC bias loss. The coefficient is less than 1 and decreases with the increase of DC and trigger angle of the converter. (2) Under the same DC, the larger the trigger angle of the converter is, the smaller the eddy current loss of the tank. (3) When the converter transformer on the inverter side is DC-biased, the eddy current loss of its tank is generally larger than that on the rectifier side, so the converter transformer on the inverter side is more vulnerable to the DC bias.
Huang Tianchao,Wang Zezhong,Li Yuyan. The Influence of Converter Transformer DC Bias on Eddy Current Loss of Tank[J]. Transactions of China Electrotechnical Society, 2023, 38(8): 2004-2014.
[1] Kulkarni S V, Khaparde S A.Transformer engineering: design, technology, and diagnostics[M]. 2nd Ed, Boca Raton: CRC Press, 2012. [2] Smajic J, Hughes J, Steinmetz T, et al.Numerical computation of ohmic and eddy-current winding losses of converter transformers including higher harmonics of load current[J]. IEEE Transactions on Magnetics, 2012, 48(2): 827-830. [3] Liu Yaqing, Zhang Dandan, Li Zhenbiao, et al.Calculation method of winding eddy-current losses for high-voltage direct current converter trans- formers[J]. IET Electric Power Applications, 2016, 10(6), 488-497. [4] 潘超, 米俭, 王格万, 等. 基于场路耦合的变压器绕组匝间短路电磁谐响应分析方法[J]. 电工技术学报, 2019, 34(4): 673-682. Pan Chao, Mi Jian, Wang Gewan, et al.Electro- magnetic harmonic response analysis method of inter-turn short circuit in transformer winding based on field circuit coupling[J]. Transactions of China Electrotechnical Society, 2019, 34(4): 673-682. [5] 李永建, 闫鑫笑, 张长庚, 等. 基于磁-热-流耦合模型的变压器损耗计算和热点预测[J]. 电工技术学报, 2020, 35(21): 4483-4491. Li Yongjian, Yan Xinxiao, Zhang Changgeng, et al.Numerical prediction of losses and local overheating in transformer windings based on magnetic-thermal- fluid model[J]. Transactions of China Electro- technical Society, 2020, 35(21): 4483-4491. [6] Wang Qingpeng, Bai Baodong, Chen Dezhi, et al.Study of insulation material properties subjected to nonlinear AC-DC composite electric field for con- verter transformer[J]. IEEE Transactions on Mag- netics, 2019, 55(2): 1-4. [7] 李冰, 王泽忠, 刘海波, 等. 直流偏磁下500 kV单相变压器振动噪声的试验研究[J]. 电工技术学报, 2021, 36(13): 2801-2811. Li Bing, Wang Zezhong, Liu Haibo, et al.Experiment on vibro-acoustic characteristic of 500 kV single- phase transformer under DC-bias[J]. Transactions of China Electrotechnical Society, 2021, 36(13): 2801-2811. [8] Liu Chunming, Liu Lianguang, Pirjola R.Geomag- netically induced currents in the high-voltage power grid in China[J]. IEEE Transactions on Power Delivery, 2009, 24(4), 2368-2374. [9] Emanuel A E, Wang X.Estimation of loss of life of power transformers supplying nonlinear loads[J]. IEEE Transactions on Power Apparatus and Systems, 1985 104(3): 628-636. [10] Ram B S, Forrest J A C, Swift G W. Effects of harmonics on converter transformer load losses[J]. IEEE Transactions on Power Delivery, 1988, 3(3): 1059-1066. [11] Forrest J A C. Harmonic load losses in HVDC converter transformers[J]. IEEE Transactions on Power Delivery, 1991, 6(1): 153-157. [12] Liu Yaqing, Zhang Dandan, Li Zhenbiao, et al.Study of the stray losses calculation in structural parts for HVDC converter transformers based on the TEAM Problem 21 Family[J]. IEEE Transactions on Power Delivery, 2016, 31(2): 605-612. [13] 赵小军, 王佳雯, 刘洋, 等. 谐波激励下变压器结构件杂散损耗的模拟与验证[J]. 中国电机工程学报, 2020, 40(2): 652-663. Zhao Xiaojun, Wang Jiawen, Liu Yang, et al.Simu- lation and verification of stray-field losses in structural components of transformers under multi- harmonic excitation[J]. Proceedings of the CSEE, 2020, 40(2): 652-663. [14] 张良县, 陈模生, 于健, 等. 特高压换流变压器涡流损耗计算与屏蔽分析[J]. 变压器, 2013, 50(3): 15-21. Zhang Liangxian, Chen Mosheng, Yu Jian, et al.Eddy current loss calculation and shield analysis of UHV converter transformer[J]. Transformer, 2013, 50(3): 15-21. [15] 黄天超, 王泽忠. 特高压换流变压器拉板损耗的频率特性分析[J]. 电工技术学报, 2021, 36(19): 4132-4139. Huang Tianchao, Wang Zezhong.Frequency charac- eristic analysis of flitch plate losses in UHV converter transformer[J]. Transactions of China Electrotech- nical Society, 2021, 36(19): 4132-4139. [16] Zhang B, Liu L, Liu Y, et al.Effect of geomag- netically induced current on the loss of transformer tank[J]. IET Electric Power Applications, 2010, 4(5), 373-379. [17] Yao Yingying, Chang S K, Ni Guangzheng, et al.3-D nonlinear transient eddy current calculation of online power transformer under DC bias[J]. IEEE Transa- ctions on Magnetics, 2005 ,41(5): 1840-1843. [18] 澹台乐琰, 韩肖清, 王磊, 等. 一种用于变压器直流偏磁状态下的改进型Jiles-Atherton模型[J]. 电网技术, 2020, 44(1): 122-132. TanTai Leyan, Han Xiaoqing, Wang Lei, et al. An improved Jiles-Atherton model for DC bias of transformer[J]. Power System Technology, 2020, 44(1): 122-132. [19] 赵志刚, 马习纹, 姬俊安. 基于Energetic模型的直流偏磁条件下电工钢片磁特性模拟及实验验证[J]. 中国电机工程学报, 2020, 40(14): 4656-4665, 4743. Zhao Zhigang, Ma Xiwen, Ji Junan.Simulation and experimental verification of magnetic characteristics of electrical steel sheet under DC bias based on energetic model[J]. Proceedings of the CSEE, 2020, 40(14): 4656-4665, 4743. [20] 李明洋, 张俊双, 李海明, 等. 500 kV单相变压器直流偏磁下损耗及绕组热点温度的计算分析[J]. 电工电能新技术, 2021, 40(8): 51-59. Li Mingyang, Zhang Junshuang, Li Haiming, et al.Calculation and analysis of loss and winding hot spot temperature under DC bias of 500 kV single-phase transformer[J]. Advanced Technology of Electrical Engineering and Energy, 2021, 40(8): 51-59. [21] 王泽忠, 李明洋, 宣梦真, 等. 单相四柱式变压器直流偏磁下的温升试验及仿真分析[J]. 电工技术学报, 2021, 36(5): 1006-1013. Wang Zezhong, Li Mingyang, Xuan Mengzhen, et al.Temperature rise test and simulation of single-phase four-column transformer under DC-bias[J]. Transa- ctions of China Electrotechnical Society, 2021, 36(5): 1006-1013.
2023, Vol. 38 
