Continuous Transient and Steady-State Control for Dual-Active Bridge Converters with Bidirectional Charge Control

Dual-active bridge converters offer a frequently used solution for isolated, bidirectional power conversion. A major drawback of the state-of-the-art control strategies for this type of converter is the incapability of handling transient performance, leading to undesired behaviour of the converter, e.g. a DC-bias in the inductor current and hard-switching of the switches. This paper presents an innovative charge-based control algorithm that is able to produce identical operation in terms of bidirectional power displacement and inductor current with respect to the state-of-the-art control methods in steady-state. Meanwhile, it offers dead-beat control during transients without losing the advantageous properties such as zero voltage switching, whenever possible, and fixed frequency operation. The control is based on the classical piecewise-linear model of the inductor current in the dual active bridge converter, extended with a model of the charge displacement within the converter. From this set of equations, the desired power displacement between subsequent zero current crossings is described as a function of the switching events of the primary and secondary active bridges. The proposed method is described analytically as well as verified through simulations for bidirectional power displacement and bipolar operation of both the primary and secondary connected voltage-sourced active bridges.