General strategy for multiphase and multilevel system based on analytical meaning of PWM

Multilevel converters have excellent performance in power application, especially in high-power medium voltage fields. To find an effective and general strategy for multilevel and multiphase system is a challenge attracting many researchers. This paper analyses the basic analytical meaning of PWM strategy, which is to implement an analog continuous reference value by means of several available discrete values of converters. Brief derivation of multilevel control strategy for one phase leg of a converter gives basic analytical characters of space vector modulation (SVM) in simple converter topology. Based on conclusions in one phase leg, general PWM strategy for multiphase converter is generalized without depending on the number of phases. Simulation results in a 3-phase 6-level systems and a 4-phase 5-level system show validity of the general PWM strategy for multiphase and multilevel system.