基于小波变换和HHT的分布式并网系统谐波检测方法

摘要

In distributed connected grid system, there is serious harmonic pollution caused by wide use of inverter units and access of nonlinear loads. The traditional detection methods such as Fast Fourier Transform and wavelet analysis heavily depend on synchronous signal detection or basis functions selection, and don’t satisfy the requirements of the harmonic detection of micro grid environment. Therefore, a novel harmonic detection and analysis method under the mode of micro-sources connected in parauel is proposed combining the wavelet transform with HHT. The method uses multi resolution analysis of wavelet transform to process the original signal. Then, a series of intrinsic mode function (IMF) components are obtained from the processed signal by using empirical mode decomposition algorithm, and the fundamental component and harmonic are extracted from the IMF components. Finally, the frequency and amplitude of signal are calculated by using the Hilbert transform. Simulation results demonstrate that the proposed algorithm has high precision and good real-time characteristics. Furthermore, the algorithm can satisfy the requirements of the harmonic detection of distributed connected grid system.%在分布式电源并网系统中，大量逆变装置的使用与非线性负载的接入，给电网带来严重的谐波污染，传统的检测方法（如：快速傅里叶变换、小波分析等）对同步信号检测、基函数选取有较大的依赖性，难以适应微电网环境下的谐波检测要求。为此，结合小波变换与HHT，提出一种新的微电源并网模式下的谐波检测与分析方法。该方法利用小波变换多分辨率分析思想对信号进行划分，并对划分后的信号进行经验模态分解，得到一系列的经验模态函数（ intrinsic mode function ,IMF），并从IMF分量中提取出基波分量和高次谐波；再对IMF分量进行Hilbert变换得到信号的频率、幅值信息。仿真实验表明该算法的谐波分析精度高，实时性好，能满足分布式并网系统的谐波检测要求。