基于Hermite插值的时变信号谐波测量研究

Time-varying signal harmonic measurement based on Hermite interpolation

针对传统的基于FFT的谐波测量方法在用于测量电力网络信号,尤其是非稳态周期信号等时变信号时存在着较大误差的问题,采用了一种在时域插值的方法对非同步采样序列进行同步化,首先利用过零检测来确定信号的实际频率,根据实际频率确定了理想采样间隔并重新定位了理想采样序列的采样位置。再对理想采样点周围的实际采样值采用Hermite插值算法得到了理想采样值并对采样序列进行了二次同步化。最后对同步化后的理想序列采用FFT变换以分析其频谱。在基频偏移固定和基频不断波动的两种情况下进行仿真计算。研究结果表明,Hermite插值同步算法能够适用于上述两种情况的谐波测量,在兼顾计算效率的同时,满足了GBT 17626.7—2008国标规定的精度要求,具有一定实用性。

Aiming at the problem that traditional harmonic measurement methods based on FFT lead to a larger error in the measurement of the harmonic signal in power grid,especially the time-varying signal such as unsteady periodic signal and so on. A method of time domain interpolation was used to synchronize the asynchronous sampling signal. First of all,zero crossing detection was used to determine the actual frequency of the signal and reposition the ideal sampling sequence according to the the ideal sampling interval,then the signal was synchronized by applying Hermite interpolation algorithm on the actual sampling value. Finally,the spectrum of signal would be analyzed with the help of FFT transform. The calculation was proceded in two situations of the fundamental frequency offset is fixed and fundamental frequency is fluctuating. The results indicate that hermite interpolation synchronization algorithm can be applied to the above two cases. Taking computational efficiency into account,it can meet the accuracy requirement of GBT 17626. 7—2008 at the same time. The Hermite interpolation synchronization algorithm is a kind of practical method.