Backstepping Nonlinear Control of Three Phase AC/DC PWM Converters

We are considering the problem of controlling three-phase AC/DC switched power converters of the Boost type. The control objectives are twofold: (i) regulating the output voltage vo to a desired reference value, (ii) assuring a unitary power factor by enforcing the voltage and the current delivered by the electric network to be in phase. The considered problem is dealt by designing a cascade-structure nonlinear controller. The inner controller loop regulates the active power provided by the network; it is built-up using the backstepping design approach. The outer loop regulates the converter squared-output voltage using a PI regulator. Such a simple solution is made possible using adequate model transformations. The controller thus obtained is shown to achieve the control objectives and proves to be robust with respect to load changes.