The document describes an extended-phase-shift (EPS) control method for isolated bidirectional DC-DC converters used in power distribution for microgrids. EPS control adds an inner phase-shift ratio between switch driving signals in addition to the outer phase-shift ratio of traditional phase-shift control. This decreases the backflow power effect seen in traditional control, expanding the power regulating range and reducing current stress compared to traditional control. The document analyzes the operation principle and eight modes of the converter under EPS control through circuit diagrams and mathematical equations.