基于组合式开关的三相变压器励磁涌流抑制策略

针对变压器在空载或者轻载的情况下合闸通电可能引起一次绕组流过励磁涌流等问题，提出一种新颖的组合式开关分相控制思路：通过分析原边采用星形不接地连接方式的三相空载变压器的投切暂态过程，推导了空载变压器在投切瞬间的关联磁链状态，进而反推得到考虑剩余磁通时抑制空载变压器合闸涌流的动态最佳投切相角，改变依赖剩磁测量电路、预先设定固定相角的现有相控模式；建立基于ATP/EMTP的电力变压器模型以模拟其在接通和分断的瞬态过程，获得投切瞬间的电压、电流、磁通等参数特征，验证了所提分相控制原理，给出了控制规律；为了实现分相控制策略，设计一种具有逻辑通信功能的新型三工作模态单极开关控制拓扑，对单极开关进行动态组合，可实现各极触头在最佳相位协调动作、统一控制；搭建硬件控制平台，验证所提控制策略可有效将励磁涌流限制在随机合闸时涌流大小的3%左右。

Inrush current suppression strategy of three-phase transformer based on combined-switches

Aiming at the problem that the primary windings may flow through the inrush current when the transformer is switched on under the condition of no-load or light-load, a novel individual phase control idea based on combined-switches is proposed. Based on analyzing the transient switching process of three-phase no-load transformer whose primary side adopts the star-shaped ungrounded connection mode, the state of the connected flux linkage at the switching moment of the no-load transformer is deduced, then the optimal dynamic switching angle for suppressing the switching inrush current is obtained considering the residual flux, which changes the existing phase control mode depending on the residual flux measurement circuit and the pre-set fixed phase angle. The power transformer model based on ATP/EMTP is built to simulate the transient switching-on and switching-off process, and the voltage, current and magnetic flux characteristics at the switching moment are obtained. The proposed individual phase control principle is verified and then the control law is given. A novel single-pole switch control topology with three operation modes and logical communication function is designed for performing the individual phase control strategy. The dynamic combination of single-pole switches can realize the coordinated action and unified control of each pole contact in the optimal phase. The hardware control platform is built to verify that the proposed control strategy can effectively limit the inrush current to about 3% of the inrush current in random switching.