非均匀采样和最小二乘法在间谐波检测中的应用

间谐波的频率是基波频率的非整数倍，并且幅值一般远小于基波和谐波的幅值，这些特点决定了对它的检测难于对谐波的检测。该文提出一种基于非均匀采样和最小二乘法的间谐波检测方法。非均匀采样由于其不受采样频率限制、频率分辨率高及抗混叠的优点，能在短数据长度下准确地检测出信号中相近的频率成分，并实现低采样频率下的高阶谐波测量。最小二乘法则可解决由于非均匀采样带来的频谱噪声问题，逐次消除检测出的大幅值信号，从而检测出幅值较小的间谐波信号，并准确估计出间谐波的幅值和相位。仿真实验表明：该方法可准确地检测出频率与基频相近，幅值远小于基波的多个间谐波，及实现低采样频率下的高阶谐波测量

Application of Nonuniformly Sampling and Least Square Technique in Interharmonic Measurement

Interharmonics frequencies are not integer multiple of the fundamental frequency, and interharmonics amplitudes are far less than fundamental amplitude and harmonics amplitudes, which mean hign sensitivity to desynchronization problems, so it’s difficult to estimate interharmonics. In this paper, a new method based on nonuniformly sampling and least square (LS) technique was proposed to estimate the interharmonics. The nonuniformly sampling has following advantages: alias-free、sampling frequency need not obey the Nyquist limit、and higher frequency resolution. So the nonuniformly sampling can measure the signals which their frequencies component are close, and can implement the higher frequencies measurement with lower sampling frequency. However, the nonuniformly sampling exists the noise in spectrum analysis, so it’s difficult to estimate the low amplitude signals. Least square technique can work out this problem by eliminating the maximal amplitude signal estimated by nonuniformly sampling, sequentially the low amplitude signals can be estimated; in addition, the application of LS can estimate the amplitudes and phases of the signals exactly. The results of experiments show that the proposed method can estimate the interharmonics exactly, even if the interharmonics frequencies are close the fundamental frequency and interharmonics amplitudes are far less than fundamental amplitude; and can measure high order interharmonics with lower sampling frequency.