Correlation Study of Voltage Fluctuation and Inter-Harmonics in Distribution Network

This paper presents an investigation into the relationship between voltage fluctuation and inter-harmonics in distribution network based on modulation theory. It is verified by Matlab/Simulink simulation and physical tests. The modulation theory, commonly used for analysis of harmonics, is used to analyze the inter-harmonics. A switching function of a rectangle waveform is used to describe a diode or thyristor´s commutation status. The input current and output voltage of the rectifier can be described by the final waveforms of some sine function modulated by the switching function. And the inter-harmonics characteristics can be obtained by the Fourier analysis of these waveforms. It can be proved that if there are some fluctuations in the voltage source, there will be abundant inter-harmonics in the current. In order to investigate the validity of analysis and simulation, the physical experiments are finished with electric interruption generator (IG).