Control strategy for the double-boost converter in continuous conduction mode applied to power factor correction

This paper deals with the control strategy for the double boost converter in power factor correction (PFC) application, working in continuous conduction mode (CCM). This converter is based on the classic boost converter split into two parallel modules of power processing; each one of these modules process half of the nominal power of the converter. Technical literature concerning this converter does not analyze in detail some very important control aspects and it seems that it is still lacking a general control strategy for such converter. This subject is developed in the present paper. This is done by converter modeling based upon the PWM switch model. The model obtained, verified by simulations, points to a multivariable control system, since the converter output voltages and the control variables (duty cycle of the two active switches) are strongly coupled. The dynamic uncoupling technique is applied in order to overcome this undesirable characteristic and to design the voltage and current compensation loops. Each module of power processing has a current mode controlled PFC circuit with a current-regulation inner loop and a voltage-regulation outer loop and the dynamic uncoupling is performed over the former. Numerical simulation results of the behavior of the double-boost converter for power factor correction application are presented.