Redefining a New-Formed Average Model for Three-Phase Boost Rectifiers/Voltage Source Inverters

Average model of three-phase PWM converters is important in both theory and practical engineering. To remedy defects possessed by the existing average models of three-phase boost rectifiers and voltage source inverters (VSI), this paper proposes and derives another new-formed models that are easy-to-use and more suitable for computer simulation. During establishing switching models, the number of independent state variables as well as independent state equations are definitely determined to avoid redundant equations when dealing with circuits that contain cut set purely consisting of inductors or voltage loop purely consisting of capacitors; during deriving average models, redundant variables are properly introduced and added into models, which makes the models easy to be understood and easy to be used. Inductor currents are taken directly as state variables. No extra assumptions are made except relying only on KCL and KVL. Requirements to three-phase AC voltages are effectively removed; therefore the models are suitable for any input/output voltage waveforms, regardless whether they are sinusoidal or non-sinusoidal, balanced or unbalanced, symmetrical or asymmetrical. Simulation examples are provided to verify the models´ validity.