Multivariable DC Bias Control of a High-Power ACDC Dual-Active-Bridge-Based Converter

This article addresses the dc magnetization issue in high-power single-stage dual active bridge (DAB)-based converters. A multivariable control strategy capable of simultaneously regulating the dc bias currents is applied to an integrated ac-dc topology. The control approach relies on two input variables, the magnetizing current, and the secondary current dc offset, and two outputs, that is, the duty cycles applied to the primary-side and secondary-side switches. The currents are measured by Hall sensors comprising several samples to average the offset values. The locations of samples and the measurement accuracy are discussed to validate the acquisition concept. The transformer is modeled using state-space equations and the controllers are tuned using state feedback associated with an augmented system to achieve robust reference tracking and disturbance rejection. The controller is designed based on the Lyapunov equation. Experimental results are presented and discussed to validate the control strategy applied to an integrated ac-dc converter rated at 8.33 kW. Steady-state and dynamic results show that the introduced solution can eliminate the dc bias of all currents even during load changes, without significantly affecting the harmonic content of the acinput current.