Controle de corrente digital de sistemas de potência desequilibrados contendo conversores estáticos.

Abstract

This work aims of examine the modelling and control of unbalanced three-phase threewire power electronic systems. The three-phase sj-stera is converted into an equivalents two-phase system to represent the transient and steady-state behavior of unbalanced loads being supplied by PWM converters. The definition of the current control strategy for the unbalanced system is based on the equivalent two-phase model. The control strategy proposed is derived from the double controller scheme that employs one controller for the positive sequence and another for the negative sequence. The controller structure is simpler than the double controller scheme in which is based on a single controller for the positive and negative sequences. Two types of controllers are discussed, one based on the PI approach and another based on the PID approach. Both controllers can be implemented digitally in the stationary reference frame. An extension of the control strategy concerns coordinate transformation matrices in which convert the unbalanced system into an equivalent decoupled two-phase system depending on the type of unbalancing. This controller can also be Implemented in the stationary refence frame. The current control considering the presence of low frequency harmonic in the system is also addressed. The proposed control laws are implemented in a microcomputer- based system at the stationary reference frame. The simulation and experimental results demonstrate the validity of the proposed methodology.