Research On Overload Protection And Power Management Of Dynamic Positioning Vessel Propulsions

With the rapid development of economic and the gradual depletion of land resources,people gradually turn to explore the vast ocean resources. Dynamic positioning vessel, thesurface ship and marine structure floating devices, equipped with a dynamic positioningsystem is the major equipment for sea resources exploration and acquisition. The ship’sdynamic positioning operations in ocean are quite different, which are often likely to face thewinds, waves, sea currents and other harsh conditions. Dynamic positioning system obtainsthe environment forces of winds, waves and sea currents and others by the signal measuringsystem to control the propulsion system, which can make the vessel keep certain position anddirection on the sea. In order to withstand harsh working conditions, the propulsion loadcapacity is generally large, accounting for almost80%of total electrical load of the wholeship, and the propulsion load always fluctuates. Therefore, it is of great significance toresearch on the limit and management of dynamic positioning vessel propulsion load forensuring the high security and reliability.In order to protect high safety and reliability of the dynamic positioning vessel,50000DWT Semi-Submersible Lift Transportation Vessel has been taken for the mother ship, andthe dynamic positioning vessel’s propulsion load limit and management have been studied.The main contents of the paper as follows:1.In order to study dynamic positioning vessel’s propulsion load limit and management,based on the analyses of diesel engine-generator system, the SVPWM control method ofpropulsion motor, and propulsion propeller, a integrate simulation platform of mainpropulsion system was established. In the environment of Matlab/Simulink, the independentfunction blocks, such as engine-generator system block, propulsion motor SVPWM controlblock, propeller block, have been modeled and integrated organically, then established aintegrate platform of electric propulsion system.2. The research of dynamic propulsion load limit method based on online availablepower of the generator set has been done in this paper. By real-time computing generationsystems available power, it has been considered the propeller thrust losses and otherdisturbance factors from the measurement device, and been ultimately calculated theoptimized maximum allowable given value of speed and thrust for each propeller.3. The dynamic positioning vessel propulsion power monitoring software was designedby the use of VC++IDE, and the Matlab/Simulink simulation model data was imported into power monitoring software to achieve real-time monitoring and power overload alarm.Finally, the results of integration testing simulation show that dynamic propulsion loadlimit method based on online available power of the generator set can limit the suddenoverload dynamically well, and can provide a more secure and reliable electric power supplyand propulsion power support for the dynamic positioning vessel.