Overmodulation in three-phase electronic key bridges of the converter-electric motor system

To ensure the operability of a circuit with three-phase pulse width modulation, it is necessary to meet the conditions of operability. One of the most important conditions is to exclude the phenomenon of overmodulation. To obtain the boundary values of the variables that determine the quality of modulation, it is necessary to study the phenomenon of overmodulation in various modes of operation of a three-phase converter. New modulating functions with constraints have been introduced to analyze the phenomena associated with overmodulation. Methods of analysis of electrical circuits have been used. The processes of three-phase pulse width modulation in the overmodulation mode have been studied. An assessment of the effect of overmodulation on the variables that determine the quality of the modulation process has been made. The boundary amplitude coefficient of a three-phase bridge has been determined, at which a three-phase overmodulation mode occurs. The results can be used to develop algorithms for controlling frequency converters in frequency control systems of electric drives.