The centralized output-parallel dual-active-bridge (OP-DAB) dc-dc system is a promising candidate for achieving isolated dc-dc energy conversion with large current and power rating. To implement the flexible power sharing performance of the OP-DAB dc-dc converter, a simple tunable power sharing (TPS) strategy is proposed with the single-phase-shift method in this article. Based on the TPS strategy, the excellent dynamic performance under disturbances of input voltage for each module and load resistor can be provided. However, inaccurate circuit-parameter information always damages the power sharing performance among different DAB converters. Therefore, the comprehensive circuit-parameter estimating schemes proposed for different conditions of the OP-DAB dc-dc system including the start-up process, the working process and plugging-in a new DAB dc-dc converter, respectively. Moreover, the hot swap (plug-in and plug-out) control methods of the DAB converter without large influence on output voltage is also discussed in detail. Experimental results are obtained to verify the analysis in this article and the excellent performance of the proposed methods.