Fast and Flexible Selective Harmonic Extraction Methods Based on the Generalized Discrete Fourier Transform
Fast and Flexible Selective Harmonic Extraction Methods Based on the Generalized Discrete Fourier Transform
复制标题
基于广义离散傅里叶变换的快速灵活选择性谐波提取方法
DOI：
10.1109/tpel.2017.2703138
复制
发表时间：
2018-04-01
影响因子：
6.7
通讯作者：
Xing, Yan
中科院分区：
文献类型：
--
作者：
Liu, Huawu;Hu, Haibing;Xing, Yan
谐波选择性提取在电能质量评估、谐波补偿等方面有着重要的作用，其中基于离散傅里叶变换（DFT）的谐波选择性提取算法以其简单、选择性滤波等优点得到了广泛的应用。然而，DFT具有诸如动态缓慢和对频率变化敏感的缺点。为了克服这些缺点，提出了一种改进和扩展的DFT-广义DFT（GDFT）。本文揭示了传统的DFT可以看作是一个梳状滤波器串联复杂的谐振器，DFT依赖于零极点相消的谐波提取机制。更重要的是，DFT慢瞬态响应背后的关键原因是梳状滤波器引入的大延迟。因此，本文提出根据输入信号的特定谐波模式重新配置梳状滤波器，以改善系统的动态响应和灵活性。GDFT不仅保持了简单性和选择性滤波特性的优点，而且具有快速瞬态特性，对于典型应用，约为0.3个基本周期，这比传统DFT的一个周期的建立时间短得多。一个锁相环块也被纳入谐波检测系统，以处理可能在实际应用中的大的频率变化。大量的测试提供了验证所提出的方法的有效性。
Selective harmonic extraction plays an important role in power quality assessment, harmonic compensation, and so on. Among the various methods, discrete Fourier transform (DFT)-based algorithms has found wide and popular applications due to advantages like simplicity and excellent selectively filtering properties. However, DFT suffers from disadvantages like slow dynamics and sensitivity to frequency variations. In order to alleviate these drawbacks, an improved and extended DFT—generalized DFT (GDFT) is proposed. It is revealed in this paper that the conventional DFT can be viewed as a comb filter connected in series with complex resonators, and DFT relies on the mechanism of pole-zero cancellation for harmonic extraction. More importantly, the key reason behind the DFT slow transient responses is the large delay introduced by the comb filter. Therefore, this paper proposed to reconfigure the comb filter according to specific harmonic patterns of the input signal for improving the dynamic responses and system flexibility. The proposed GDFT not only maintains the advantages of simplicity and selectively filtering properties but also features fast transients, around 0.3 fundamental cycle for typical applications, which is much shorter than the one-cycle settling time of the conventional DFT. A phase-locked-loop block is also incorporated into the harmonic-detection system to deal with possibly large frequency variations in practical applications. Extensive tests are provided to validate effectiveness of the proposed method.