直流偏磁对换流变压器运行影响分析

Analysis on DC Bias Impact on Converter Transformers Operation

特高压直流工程因为输送容量大、传输距离远等优势在近年得到迅速发展和工程实践。但特高压直流工程一直存在直流偏磁现象,直流偏磁电流会导致特高压直流换流变压器的励磁电流畸变,引起振动和噪声加剧等不利影响,严重情况下会威胁换流变的安全稳定运行。首先对直流偏磁产生的原理进行了分析,通过计算确定了实际特高压直流工程中各因素的影响程度,搭建了特高压换流变铁芯模型对其励磁特性进行了仿真研究和试验验证。并利用有限元仿真对直流偏磁影响下的换流变振动和噪声进行了多物理场耦合建模和计算分析。研究结果对后续特高压直流工程中换流变压器的研制及换流站噪声超标的解决措施具有重要指导意义。

The UHVDC projects have been rapidly developed and practiced in recent years because of their advantages of large transmission capacity and long transmission distance. However, the DC bias phenomenon has long existed in the UHVDC projects. The DC bias current will cause the distortion of excitation current, and increase the vibration and noise of the UHVDC converter transformer, which will jeopardize the safe and stable operation of the converter transformer in severe cases. In this paper, the principle of DC bias current was firstly analyzed, then the impact level of a practical UHVDC project was determined by calculation. A UHVDC converter transformer core was constructed to simulate and test its excitation characteristics. The impacts of DC bias on transformer vibration and noise were investigated, and multiphysics coupling modeling and simulation were performed by using finite element method. The research results are of practical significance for guiding the design of converter transformers and for taking the noise reduction measures in subsequent projects.