中文摘要：

准确的直流系统模型是交直流系统故障分析和谐波计算的基础。文中在换流器开关函数模型的基础上，结合直流控制系统的故障响应特性，建立了可与交流系统直接接口的适用于交直流系统故障分析和谐波计算的直流系统等值模型；结合交流系统等值谐波网络，提出了一种交流电网故障时的高压直流输电系统谐波分析计算方法。将所提方法应用于国际大电网会议高压直流输电（CIGRE HVDC）系统标准模型和贵广Ⅱ回高压直流输电系统详细模型的谐波计算，并与PSCAD/EMTDC软件所得数字仿真结果进行比较，表明所提模型和方法准确、有效，为交直流输电系统的谐波抑制、滤波装置的配置和继电保护的整定配合等提供了定量分析依据。

英文摘要：

An accurate converter model is the foundation of AC/DC system fault analysis and harmonic calculation.Based on the dynamic switching characteristics of inverter and fault response characteristics of DC control system of various fault-types,a DC system model able to directly interface with AC systems is developed for AC/DC system fault analysis and harmonic calculation.By referring to the AC and DC power grid harmonic equivalent network,an high voltage direct current （HVDC） system harmonic calculation method suitable for AC asymmetric fault condition is proposed.The method is used in the harmonic calculation of CIGRE HVDC system and Guiguang Ⅱ HVDC system.Compared with simulation results using PSCAD/EMTDC software,the results obtained show that the proposed model and method are accurate and effective,providing a basis for quantitative analysis of harmonic mitigation,filter configuration and protection setting of the AC/DC system.