Parallel operation of half-bridge converters with current-doubler rectifier using feedback linearization control

This paper presents a nonlinear controller applied to a parallel connected system of half-bridge with current-doubler rectifier (HB-CDR) converters. The proposed control scheme is able to decouple the output-voltage dynamics from the input-stage variables, endowing high robustness of the output voltage against external disturbances. In addition, the inner average-current loop of the controller achieves good load sharing among modules in spite their parametric variations. The controller design is developed in three steps. First, the large-signal model of the parallel-connected HB-CDR system is obtained. Second, the controller expression is conceived through input-output linearization theory taking into account two control objectives: the regulation of the output-voltage and the equal current distribution among modules. And third, the control parameters are determined to obtain a proper dynamics, while ensuring the stability of the whole system.