The invention discloses a power island, comprising an SPC (Source Power Conditioner), an LPC (Load Power Conditioner), a DCS (DC Converter System), an emergency power supply system and an AC bus, wherein the SPC is formed by m sets of three single-phase conversion systems composed of 3m series transformers and 3m single-phase convertors; the LPC is formed by n sets of three single-phase conversion systems composed of 3n series transformers and 3n single-phase convertors; the DCS is formed by two sets of three-phase three-wire convertors spare for each other and a DC bus. According to the invention, m paths of power supply provide power for n paths of important loads through the power island; the power island can realize the seamless switching among a plurality of paths of power supply, rapid voltage support, seamless grid connection of an emergency power supply system, and maintenance of load normal work, and meanwhile realize voltage harmonic wave, current harmonic wave, and reactive power compensation; in addition, the power island can restrain impact load active fluctuation, realize peak load shifting, and eliminate the circulation caused by direct parallel connection of a plurality of paths of power supply or active loads; besides, the power island can isolate the fault current generated in case of load faults, and meet the requirements of high reliability and high quality for electric energy by important loads.