Direct-current networking ship electric propulsion system and method

The invention discloses a direct-current networking ship electric propulsion system, which comprises a direct-current bus for connecting devices in the system to perform energy transmission; an energystorage device which is connected with the direct-current bus and used for storing or providing required electric energy for the system; a power device which is positioned between the direct-currentbus and the propeller and is used for controlling the starting and stopping states of various internal power sources by utilizing electric energy obtained from the direct-current bus and/or the current fuel capacity of the system according to different ship working conditions and combining a power distribution principle; a corresponding coupling or decoupling relation is formed between each type of power sources and the propeller, and mechanical energy corresponding to the system propelling power conforming to the current ship working condition and provided by different power source combinations is output to a propelle