基于自适应互补LMD方法的谐波检测与分析

针对电力系统信号非线性、非稳态的特征,自适应分解方法具有高效简便的处理优势。但此类方法在加噪参数选择时存在需要人为经验性确定的缺点,为此,提出一种自适应互补LMD(ACLMD)方法。该方法通过对加噪辅助分解方法噪声准则的研究,引入间距标准差(STD)与信噪比(SNR)两个参数作为分解性能评价指标,自适应确定最优加噪幅值与集总分解次数,且加噪形式采用正负成对的形式,抑制了分解过程中的残余噪声。并对标准LMD方法特征提取步骤进行改进,将分解所得的乘积函数进行Hilbert变换提取瞬时特征参数,消除了阶跃分量干扰下纯调频函数提取范围的限制。最后将改进的方法运用在谐波检测中,通过仿真实验验证所提方法既可以有效提取谐波的特征参数,也可以准确定位扰动的时间,且具有一定的抗噪性能。

Harmonic detection and analysis based on adaptive complementary LMD method

Aiming at the non-linear and non-stationary characteristics of power system signals, the adaptive decomposition method has efficient and simple advantages in processing signals.However,there is a shortcoming that the selection of additive noise parameters in such methods are required to be obtained artificially.To counter the above-mentioned shortage,an adaptively complementary LMD(AELMD) method was proposed.In the proposed method,the added-noise principle of noise assisted decomposition method is analyzed,and the two parameters(Standard Deviation and Signal-to-Noise) are taken as an evaluation index of adding noise to adaptively determine the optimal amplitude of additive white-noise and number of ensemble trials.And the additive noises are added in the form of positive and negative pairs to the targeted signal,which inhibits residual noise in the decomposition process.And then,the feature extraction steps in standard LMD method are modified,the decomposed product functions are extracted the instantaneous characteristic parameters by Hilbert transformation,which eliminates the limitation of the extraction range of pure frequency modulation function under step component interference.In the last, the modified method is utilized in the harmonic detection,through simulation experiments verify that this method is not only able to effectively extract harmonics characteristic parameters,but also accurately locate disturbances time, and has a certain anti-noise performance as well.