Short-Time Fourier Transform Based Transient Analysis of VSC Interfaced Point-to-Point DC System
Short-Time Fourier Transform Based Transient Analysis of VSC Interfaced Point-to-Point DC System
复制标题
DOI：
10.1109/tie.2017.2758745
复制
发表时间：
2018-05-01
影响因子：
7.7
通讯作者：
Geddada, Nagesh
中科院分区：
文献类型：
--
作者：
Satpathi, Kuntal;Yeap, Yew Ming;Geddada, Nagesh
电压源换流器（VSC）接口直流系统的瞬态响应与交流系统有很大的不同。直流侧电容器的快速放电电流和续流二极管在直流电网短路时的脆弱性要求暂态检测算法在几毫秒内执行。直流电网中快速上升的故障电流预计将具有高频分量，这可能是瞬态条件的有效指标。本文提出了利用短时傅里叶变换（STFT）在瞬态条件下的高频分量的定量调查。详细的工作原理与各种因素影响的STFT操作，如输入直流信号和窗口类型和长度的涟漪内容已被彻底调查。STFT算法能够在1 ms内检测到低阻抗故障，在2 ms内检测到高阻抗故障。此外，它能够区分短路故障和不太严重的瞬态条件，如负载突变。STFT算法进行了分析评估，并随后应用到MAT-LAB/Simulink的直流测试系统。通过缩小实验测试台获得的真实的故障电流数据进一步验证和证实了这一点。灵敏度分析和与现有的频域故障检测方法的比较，以支持所提出的方法的有效性。
The transient response of the voltage source converter (VSC) interfaced dc system is significantly different from the ac counterpart. The rapid discharge current from the dc-link capacitors and the vulnerability of the freewheeling diodes during the short circuit in dc grid demand that the transient detection algorithm executes within a few milliseconds. The rapidly rising fault current in the dc grid is expected to have high-frequency components which might be an effective indicator of the transient condition. This paper presents quantitative investigation of the high-frequency components utilizing short-time Fourier transform (STFT) during transient conditions. Detailed operating principles with various factors affecting the STFT operation such as ripple content of the input dc signal and window type and length have been thoroughly investigated. STFT algorithm is able to detect low-impedance faults within 1 ms and high-impedance faults in 2 ms. Moreover, it is able to distinguish between short-circuit fault and less severe transient conditions such as sudden load change. The STFT algorithm is evaluated analytically and subsequently applied to a MAT-LAB/Simulink based dc test system. It is further validated and substantiated with the real fault current data obtained from a scaled-down experimental testbed. Sensitivity analysis and comparison with the existing frequency-domainbased fault-detection method are done to support the efficacy of the proposed method.