Probabilistic modeling of harmonic currents produced by a twelve-pulse AC/DC converter under unbalanced supply voltage

Previous work on harmonic modeling have shown that the probabilistic approach is suitable to harmonic prediction since it allows to take into account the randomly varying operating conditions of static converters. Although the six-pulse AC/DC power converter has already been the subject of probabilistic modeling, little consideration has been given to the twelve-pulse AC/DC power converter. In high power applications, such as large rated DC and AC drives, large rated DC power supplies, twelve-pulse AC/DC power converters are usually preferred since they allow a reduction of system disturbances due to harmonic currents. This paper presents an analysis of the random properties of harmonic currents produced by a twelve-pulse AC/DC power converter that operates under random variations of its DC load and voltage unbalance. The probability density functions of the amplitudes and the phase angles of the harmonic currents (of orders 12k±1 and 12k-6±l) are established and validated by results obtained from Monte Carlo simulations