Limitations of Current-Optimal Dual Active Bridge Modulation Strategies

In this article a frequency domain-based numerical optimization algorithm is developed to calculate multi-variable PWM control strategies for the Dual Active Bridge that optimize the RMS current circulating in the linkage inductor. A novel analysis of the results concludes the presence of an unavoidable zero current switching boundary that exists in the operational domain and separates zones of ZVS and ZCS. This boundary is then analytically derived for use in control strategies. As commutation at zero or non-negative currents can introduce large switching losses, knowledge of this boundary is crucial for Dual Active Bridge converter design.