Electrical Drive System Research Of Large Cutter Suction Dredger

As one sort of the most widely-used engineering ships in dredging project, cutter suction dredger has function of dredging sand, soil and rock, transporting mud and has advantage of high efficiency and a good adaptability. It is widely used in sea route dredging in internal river and inshore area, garden marking, de-silting and water source improving etc.Dredgeing equipments(e.g dredging pump, cutter, hoisting winch, side winch)are driven by hydraulic motor or diesel engine in traditional dredgers. Based on disadvantage of low efficiency, narrow speed adjust range, heavy maintainance duty of these two drive type have, the paper will bring forward and do research on electrical drive system of large cutter suction dredger. Electrical drive type have replaced hydraulic drive type and diesel engine drive type and become development trend of large cutter suction dredger. The system studied in the paper comprise three to four diesel engine generator, all dredging equipments are driven electromotor, and it has advantage of great operation, wide speed adjust range, high dredging efficiency and low dredging cost etc..Variable frequcney drive type for dredging equipments and its influence to ship’s performance and power grid are studied in the paper. Consumers are divided into groups according to power and their function. Considering ship’s space and equipments’ arrangement, several variable frequency drive plan are stuied. Additionally, harmonics distortion brought by frequency inverter is also studied. Via theory analysis and appliance example, electrical drive plan are maken and useful demonstration are supplied for other large cutter suction dredger.There are five chapters in this paper.Chapter 1 presents background of cutter suction dredger and concludes configuration and drive type of large cutter suction dredger constructed in domestic and abroad. Furthermore, it summarizes research content and work to do.Chapter 2 analyses characteristic of ship’s short circuit current and studies calculation method according to classification society’s requirement. Via calculation and analysis, voltage grade are decided. According to dredging equipments’ function and thier control requirement and ship’s frame arrangement, influence of variable frequency drive type to power grid are compared and last electrical frame of large cutter suction dredger are built.Chapter 3 introduces the harm of harmonics to ship’s power grid, analyses several frequency inverter in detail and calculates harmonic distortion of the ship’s power grid by special software. It also analyses several normal harmonics elimination and inhit methodes and their principle in ship and compares their advantage and disadvantage. Multi pulse solution for reducing THD is achieved and proven meeting of ship’s power grid.Chapter 4 introduces the frame of frequency convertor control system and monitoring system in large cutter sunction dredger, and presents main specification and characteristic of frequency convertor used frequently in ship. Aimed at two variable speed methods of asynchronous motor, the principle and control method of vector control and direct torque control are analysed, their advantage and disadvantage are also compared. According to equipment power, voltage, overload capacity and speed range etc. of large cutter sunction dredger, the article gives the selection of frequency inverter for reference.The last chapter, Chapter 5, summarizes main study content and relative fruit and the prospects of researches in future.