The current hardware detection methods have many drawbacks,such as poor flexibility and single function. An improved FFT algorithm considering the frequent fluctuation and half-wave symmetric characteristic of the metro power system signals was presented based on the conventional FFT method. The metro power harmonic detection system was developed based on virtual instrument. The working principle of The PC-DAQ structure scheme was adopted for hardware of this system,some sensors test-bed were reserved,a new virtual instrument test-bed was used. The software of this system was developed based on LabVIEW2009. It can use the powerful library to develop a lot of functions, the example to data acquisition, adaptive frequency tracking, harmonic a-nalysis and dynamic data display. The improved FFT algorithm used MATLAB software simulation show that the calculation of the algorithm just has a half amount of the traditional FFT,it can improve the speed of the analysis of harmonic. The system software tests show that this system can achieve the expecting functions and has the advantages of high accuracy and good expansibility.%针对地铁电网谐波具有频率波动及半波对称的特性,以及传统硬件检测方法功能单一、灵活性差等缺点,文中提出了一种改进FFT算法,并在该算法基础上设计并开发了基于虚拟仪器的地铁电网谐波监测系统.该系统硬件采用PC-DAQ结构方案,在一定硬件设备的基础上,增加虚拟仪器开发平台.系统软件采用LabVIEW2009,运用LabVIEW强大的函数库实现数据采集、频率跟踪及谐波分析、数据动态显示等多种功能.改进FFT算法在MATLAB中仿真表明,该算法是传统FFT运算量的一半,提高了运算速度；软件测试表明,该系统能够实现预期功能,并具有检测精度高、实时性及扩展性好等优点.[1-2]
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