变压器交直流混杂运行励磁状态与构件损耗

Excitation State and Component Loss in AC/DC Hybrid Operation of Transformer

针对变压器交直流混杂运行导致的金属构件局部过热问题,研究变压器励磁特性与拉板损耗的关系。建立交直流混杂模式下的变压器电磁耦合状态方程,基于能量扰动原理计算动态电感与时域电流两个状态变量,在此基础上研究励磁电流辨识方法,利用励磁电流表征变压器励磁饱和状态。通过仿真模拟与实验对比验证该方法的正确性,进一步分析变压器在不同运行方式、直流水平及负载率时拉板的漏磁和涡流损耗分布,总结其变化规律并拟合励磁状态-构件损耗的数学模型,为变压器交直流混杂运行构件损耗计算提供新方法。结果表明,变压器运行于70%负载率时,拉板损耗随直流水平提高而增大,当直流水平达到空载电流2倍时,拉板损耗提升约3倍,易出现局部过热问题。

Aiming at the partial-overheating problem of metal components in transformer caused by AC/DC hybrid operation, the relationship between excitation characteristics and tie plate loss is studied. The electromagnetic coupling state equation of transformer is constructed in AC/DC hybrid mode. Then the dynamic inductance and time-domain current named as state variables are calculated based on energy disturbance principle. Thereafter, the excitation current identification method is studied to present the excitation saturation state. And this method is proved by comparing simulation with experiments. Furthermore, the leakage flux and eddy current loss in tie plate is simulated under different operation situation. Summarizing the variation rule of abnormal feature, the mathematical model of the excitation-loss is fitted, which will be a new way for calculation of components loss in AC/DC hybrid operation. The results show that tie plate loss increases with DC level raising when the transformer operates at 70% load, and its loss increases by about 3 times when DC level is two times as high as the no-load current, which causes the problem of local overheating easily.