In recent years, the International Environmental Conventions has put great effort into green ship technology development. Following this trend, on Asia’s First Hybrid Ferry “Happiness”, SOIC established a ship-class hybrid power system . On board, the main circuit is designed with a fixed 750 voltage regulated DC bus, stand-alone rated power of 250kW supply, and total system processing power of around 1MW. It integrates digital communication between the propulsion motor, lithium battery pack, and generator set according to the SAE-J1939 standard, and calculates the load of the generator sets, power quality control, and fault current protection using real time numerical analysis. The ships installed with PMS developed by SOIC can save at least 30% fuel consumption (the operating mode will provide different fuel consumption performance).