中文摘要：

直流保护的正确动作对交直流大电网的安全稳定运行具有重要意义。为了探究换流阀故障特性以及阀故障导致直流侧100Hz谐波分量产生机理和计算方法，首先分别对整流器阀和逆变器阀误开通故障和不开通故障时的通断特性和换流器的开关函数特性进行理论分析；其次给出了换流器序分量开关函数模型，在此基础上分析了阀故障导致直流侧产生100Hz谐波分量的机理，并提出了具体的计算方法；最后基于贵广-Ⅱ回HVDC系统详细模型对该分析方法进行了仿真验证。结果表明，换流阀导通逻辑顺序的改变引起直流侧产生100Hz谐波分量，且关于100Hz谐波分量的计算方法能满足工程实际计算要求，为进一步研究直流系统100Hz保护提供理论分析基础。

英文摘要：

The correct operation of DC protection is important to the safe and stable operation of AC and DC power sys- tem. In order to study the converter valve fault characteristics and the 100Hz harmonic component mechanism caused by valve fault and their calculation method, we firstly theoretically analyzed the valve characteristic and converter valve cur- rent switching function characteristics when the rectifier valve and inverter valve have turn-on fault and not turn-on fault,respectively. Secondly, we established a model of converter sequence component switching function, analyzed the valve fault-caused mechanism of DC-side 100Hz harmonic component, and put forward the specific calculation method. Finally, on the basis of detailed model of Guiguang- II HVDC system, we simulated and verified this analysis method. It is shown that the change in logical sequence of converter valve conducting will generate 100Hz harmonic component by the DC side, and the calculation method of 100Hz harmonic component is able to meet the requirements of engineering. The result may provide the theoretical basis for the further research of DC system 100 Hz protection.