All power converters, including dual-active-bridge (DAB) DC-DC converter, cannot sustain a consistently high-efficiency performance over a wide range of operating conditions, and reconfiguration of operation mode represents a viable solution to this fundamental problem. To meet this challenge, a resonant-type three-phase DAB (3p-DAB) converter incorporating a three-phase reconfigurable resonant network (3p-RRN) has been proposed in this paper. The proposed converter can operate either as a 3p-DAB resonant immittance converter (3p-DABRIC) or a 3p-DAB series resonant converter (3p-DABSRC) to enhance its efficiency performance over a wide range of voltage conversion ratio and output power levels. In addition, the proposed converter offers the flexibility to operate with unity power factor, full-range zero-voltage switching (ZVS) and enhanced light-load efficiency under varying operating conditions by appropriate selection of the converter's operation mode. Based on a careful loss analysis and verification of the loss model by experimental measurements, it has been found that under wide range variations in voltage conversion ratio and output power levels, 3p-DABSRC delivers a more superior efficiency performance at low to medium power levels, whereas 3p-DABRIC generally achieves a higher efficiency at high power levels, and thus combination of both operation modes leads to an overall wide range high-efficiency performance.