Time Domain Analysis of Reactive Components and Optimal Modulation for Isolated Dual Active Bridge DC/DC Converters

This letter discusses the reactive components and the power factor of dual-active-bridge converters under triple-phase-shift modulation. Different from previous methods based on backflow power integral or Fourier series expansion, this letter presents a straightforward analysis and categories of reactive current through time domain analysis, and then gives a unified time domain definition of reactive current, reactive power, and power factor. Compared with all the previous definitions, the expressions of reactive components and power factor are much more concise and of a profound physical meaning. On this basis, specific calculations of reactive power and power factor are derived for all practical voltage patterns and an optimal global power factor phase shift modulation is proposed to improve the power factor on both bridges. At last, the effectiveness of analysis and proposed modulation were validated using a 500-W laboratory prototype. The results showed efficiency improvements compared to other optimal power factor modulation strategies.