柔性直流输电换流器故障特性分析及诊断研究

为了准确识别柔性直流输电电压源换流器故障类型及位置，在分析换流器故障特性的基础上，给出了一种简便快速的故障识别及定位方法。基于两电平电压源换流器的VSC-HVDC的系统仿真，分别建立了交流侧单相断线故障时直流电压、直流电流波动分量计算模型和两侧换流器故障交流电流计算模型，分析了故障换流器交流侧谐波与直流侧谐波分量的关系，给出了柔性直流输电换流器故障谐波传递规律。根据已建立的故障换流器数学模型和交直流侧谐波传递规律，以直流电流各次谐波分量、交流电流有效值和标幺化直流分量作为诊断特征量，提出了一种运算简便快速的故障定位方法，可用于识别电压源换流器中轻微故障的位置。仿真结果表明，提出的故障识别及定位方法能够在线实时准确地诊断电压源换流器轻微故障类型和位置，诊断时间最多需要35 ms。

VSC fault characteristic analysis and diagnosis research of VSC-HVDC

In order to recognize voltage source converter (VSC) of VSC-HVDC system fault type and fault location, a simple and rapid method for fault discrimination and location is presented after the analysis of fault characteristics of converter. Based on the system simulation of two-level VSC-HVDC, the DC voltage and DC current fluctuation components mathematical calculation models and two sides AC fault current mathematical calculation models under condition of single-phase disconnection fault are built respectively, the relationship between AC and DC side harmonics is analyzed, and then the VSC fault harmonic transfer law is obtained. According to the VSC fault mathematical models and harmonic transfer law, the harmonic components of DC current, RMS value of AC current and normalized DC component are taken as diagnosis characteristic quantities, then a simple and high-speed fault location method is put forward to identify minor fault locations. The simulation results show that the method presented for fault discrimination and location can accurately identify minor fault type and fault location of VSC in real time, the diagnosis time is up to 35 ms. This work is supported by Scientific Research Program of Shaanxi Education Department (No. 15JK1477).