半控型H桥子模块提高HVDC换相失败免疫力的机理

Mechanism of Semi-Controlled H-bridge Sub-Module to Improve Commutation Failure Immunity of HVDC

为提高传统直流输电(line-commutated-converter high voltage direct current,LCC-HVDC)换相能力,提出一种适用于串入LCC-HVDC阀臂的半控型H桥子模块拓扑结构。它由晶闸管和电容器构成,从提高LCC-HVDC系统阀臂电压可控性的角度增大换相电压裕度。设计了子模块的工作原理及其基本控制策略,分析了子模块晶闸管电压电流应力及电容器相关参数,仿真计算了换相失败免疫因子与子模块个数关系。PSCAD仿真表明,阀臂串入半控型H桥子模块的LCC-HVDC,系统对称及不对称故障下其换相失败发生概率明显降低。研究结果验证了子模块拓扑的有效性及可行性,为解决换相失败问题提供了一定的思路。

A semi-controlled H-bridge sub-module topology inserted into valve arms of LCC-HVDC （line- commutated-converter high voltage direct current） was proposed to improve the commutation failure immunity of HVDC. The topology assists in commutating from the viewpoint of increasing the controllability of voltage, which is composed of Thyristors and capacitor. The operating principle of sub-module and the coordinated control strategy were designed. The operation voltage and current of the sub-module switches were given by theoretical derivation. The relationship between commutation failure immunity and numbers of sub-module was further studied. The simulation results in PSCAD/EMTDC show that LCC-HVDC with semi-controlled H-bridge sub-module topology can be immune to commutation failure in both single-phase and three-phase faults to a great extent. The results demonstrate the effectiveness and feasibility of sub-module topology and it provides a new ideal for decreasing commutation failure.