Analysis of voltage disturbances caused by simultaneous amplitude and phase modulation in electric power network

Voltage distortions and disturbances in power network are an important power quality factor. Usually in literature phase disturbances are neglected and only amplitude distortions are discussed. Amplitude disturbances are interpreted as amplitude modulation (AM) of main 50 Hz frequency and considered to be the only reason of light flicker. Standard flicker measurement method is based under two not fulfilled assumptions: 1) AM with modulating frequency lower then 50 Hz carrier frequency and 2) constant carrier frequency. In the article detailed analysis of possible disturbances and it sources is presented. It is shown that AM and narrow band PM (phase modulation) take place in power network simultaneously and those two modulations interact with each other. Theoretical results are verified by field experiment.