Ultrahigh voltage modular multilevel flexible DC transmission neutral point earthing method

The invention relates to an ultrahigh voltage modular multilevel flexible DC transmission neutral point earthing method, which belongs to the field of ultrahigh voltage flexible DC transmission. The method comprises the following steps: a balancing winding is added to a transformer with Yny wiring; the capacity of the balancing winding and the voltage grade are calculated; and neutral point earthing resistance parameters are designed. A connecting transformer adopts a Ynyrd neutral point high-resistance earthing mode, and in the method, through adding a third wiring in delta connection as the balancing winding, the defect of large third harmonic loss when a power system of an early stage uses the Yny wiring transformer can be solved. The method has the advantages that the occupied area is small, an earthing transformer can be saved, the economic performance is higher, and the making difficulty is reduced. 本发明涉及种特高压模块化多电平柔性直流输电中点接地方法，属于特高压柔性直流输电领域。包括以下步骤：Yny接线的变压器增加平衡绕组；平衡绕组容量和电压等级计算；中性点接地电阻参数设计。本发明联接变压器采用Ynyr