电容隔直可控开断桥法抑制变压器直流偏磁

Blocking DC Capacitor Controllable Opening and Broken Bridge Suppression in Transformer DC Magnetic Bias

高压直流输电以单极大地回线方式运行时,会造成附近变压器直流偏磁。本文针对这一现象,提出一种中性线电容隔直可控开断桥的新电路拓扑结构,来抑制直流偏磁。与传统电容隔直电路相比,利用桥路中直流电感来限制故障初期短路电流上升变化率,且无需控制系统响应,瞬时自动投入,从而避免暂态电流冲击损坏电容器。确保了中性点有效接地,使控制系统有充足的响应时间切换工作方式。并详细给出电路的等效结构,电压、电流解析结果及电容器等电路参数的选取依据。利用PSCAD/EMTDC软件对比分析了系统故障时加入隔直装置抑制瞬态冲击电流的效果。制作了小功率的隔直实验装置,实验结果与仿真相吻合,证明了该方法的有效性和实用性。

The enormous ground return current caused by HVDC system＇s mono-pole ground return operation mode will result in transformers nearby DC biasing. This paper provides a new circuit topology of a neutral blocking DC capacitor controllable opening and broken bridge for suppressing DC biasing. Compared with the traditional blocking capacitor circuit, the increasing ratio of the fault current just after the occurrence of a fault is limited by a DC limiting reactor, which is instantaneous automatic input without control system response. As a result, it avoids the transient current shock to damage the capacitor. This method ensures neutral point effective grounding. Meanwhile, the control system has adequate response time to switch working modes. The structure of the equivalent circuit, and the analytical results of the voltage and current and are given in detail. In addition, the selected bases for parameters of capacitor are also provided. Using PSCAD/EMTDC software, it comparative analyses that the effect of suppressing transient impulse current with or without adding blocl^ing DC device under fault conditions. A blocking device prototype with low-power Results prove its validity and practicability. is established and experimentally investigated