A Low Complexity Algorithm for Efficiency Optimization of Dual Active Bridge Converters

This paper proposes a triple phase shift modulation (TPS) with an optimization technique that aims at maximizing the efficiency of the dual active bridge converter. Such a converter is often used to interface renewable or energy storage systems in smart dc power systems, where loss minimization via TPS is crucial, especially at light-load conditions. In this paper, favorable modulation parameters are found first, aiming at minimum rms currents and zero voltage switching, by considering only some fundamental converter parameters, namely, the input and output voltages, the transformer ratio, and the leakage inductance. Then, on the basis of the closed-form analytical description of the converter behavior over the determined modulation patterns, trajectories in the modulation planes that are capable of improving the total efficiency are identified. It is shown that such trajectories lead to close-to-optimal efficiency operation, which can be exploited to implement fast perturb-and-observe methods requiring just minimal converter parameters knowledge. The results are verified experimentally on a 1.5-kW prototype. It is shown that the proposed approach achieves close-to-optimal efficiency operation under different input voltages, being the error with respect to the measured optimal points obtained by a brute-force approach lower than about 0.2%.