基于FFT和小波变换的交直流并联输电系统间谐波研究

运用谐波调制理论,结合开关函数的傅里叶分析,研究了在交直流并联输电系统下,交流系统供电电源含有畸变谐波时,直流线路和交流侧都产生间谐波的机理。给出了整流侧直流电压、直流电流以及交流电流产生的间谐波的一般形式。经过小波变换除去信号中的非稳态分量以后,再使用加窗快速傅里叶变换可以很好地得出其中的稳态分量。通过一个典型交直流并联输电系统数字仿真,同时在供电电源含有畸变谐波的情况下,对交直流系统的电压和电流量进行了间谐波计算。利用傅里叶小波分析综合分析法得到的仿真结果和计算结果相比较,验证了间谐波产生机理的正确性和有效性。

Study of interharmonic in AC/DC parallel transmission system based on FFT and wavelet transform

The mechanism of interharmonic generation in AC/DC parallel transmission system is studied with the harmonic modulation theory and the Fourier analysis of switch function,which shows that when AC transmission lines contain distorted harmonics,both AC and DC sides will generate interharmonics.The general interharmonic forms of DC current and voltage at rectifier side as well as those of AC current are given.Wavelet transform is used to remove the non-steady components from the signals and the steady components are obtained using FFT transform.A typical AC/DC parallel transmission system is simulated and the interharmonics of AC/DC voltages and currents,when the power supply contains distorted harmonics,are calculated.Simulation results by proposed method are compared with the calculative results,which demonstrate its correctness and validity.