柔性直流换流阀改进运行试验方法

为了实现对柔性直流换流阀更准确的综合应力考核，针对换流阀中含有二次环流等分量的阀电流，提出了柔性直流换流阀改进运行试验方法，可满足不同功率等级下柔性直流换流阀含有不同特征电流运行工况的试验要求。首先，对柔性直流换流阀的典型运行工况进行了应力分析，重点分析了换流阀的电流特征；其次，结合应力分析，考虑到实际工程中换流阀运行时未投入环流抑制时的桥臂电流中包含较大的二倍频分量的工况，在柔性直流换流阀的阀段试验装置和不增加试验成本的基础上，通过调制控制策略，提出了针对含二次环流分量的阀电流应力和电压应力考核的试验方法，并阐述了其运行机理；最后，搭建了实际的试验系统，并进行了验证。试验结果表明，该柔性直流换流阀改进运行试验方法具有可行性和有效性。

Improved Operation Test Method for Flexible DC Converter Valve

In order to achieve more accurate comprehensive stress assessment of the flexible DC converter valve, aiming at the valve current with the second harmonic circulation in the valve, an improved operation test method for flexible DC converter valves is proposed. The method can meet the testing requirement of flexible DC converter valves in operation conditions with different characteristic currents at different power levels. Firstly, the stress analysis of the typical operation conditions of the flexible DC converter valve is carried out, focusing on the current characteristics of the valve. Secondly, combined with the stress analysis, considering that the bridge arm current contains a large second harmonic component when the converter valve is in operation without circulation suppression in the actual project, and based on the valve section test device of the flexible DC converter valve and no additional test cost, a test method for assessing valve current stress and voltage stress with the second harmonic circulation components is proposed via the modulation control strategy, and its operation mechanism is described. Finally, an actual test system is built and the method is verified. The test results show that the improved operation test method for flexible DC converter valves is feasible and effective.