MODELING OF A SHIP POWER SYSTEM SCHEME ON ELECTRIC PROPULSION

Abstract

On ships with electric propulsion systems, transformers can be eliminated to reduce power losses in the ship's electric power systems when transmitting electricity from the ship's power plant to the propeller motor. The use of transformers in the propulsion motor power supply circuit can be avoided in the case of using multilevel inverters. Transformerless power systems have one major drawback. If the loads on the galvanically unconnected three-phase windings of the same generator are different, then the voltages at the output of the windings will differ, and the stabilization system will not be able to ensure the stability of the voltage on all windings of the generator. The purpose of this work is to simulate a circuit of an electric power system in which main generators are used with one polyphase winding on the stator. These generators do not create mutual voltage distortion and provide a stable voltage on the lines of the main switchboard. The use in a ship power plant of each main generator with one polyphase winding on the stator with more than three phases, the phases of which are connected by a star or delta, as well as the use of a line of the main switchboard with the same number of phases as the windings of the main synchronous generators, makes it possible to obtain two and more systems of galvanically isolated polyphase supply voltages necessary for the operation of the frequency converter with multilevel inverters. On the basis of the scheme, in which the propeller motor is connected directly from the generating sets, a model of a transformerless electric power system has been developed and computer simulation has been carried out. In the process of modeling, the quality of the voltage of irresponsible consumers and the quality of the current in the windings of propulsion electric motors, the power supply of which was provided from frequency converters based on a two- and three-level autonomous voltage inverter, were evaluated. It is shown that the diagrams of ship power systems without transformers are characterized by stable performance.