Research On Direct Torque Control Of Marine Permanent Magnet Synchronous Motor

Marine electric propulsion is an advanced propulsion way,which makes up for the many shortcomings of mechanical propulsion and is hot reseach of at home and abroad.Direct torque control of marine permanent magnet synchronous motor is an important part of the marine electric propulsion,doing research on direct torque control of marine permanent magnet synchronous motor has great significance on marintime power of our country.After referencing a large number of related literature,this paper collectes the research status and development trend of marine electric propulsion,permanent magnet synchronous motor direct torque control technology and reduction methods of permanent magnet synchronous motor torque ripple in DTC system.This paper analyzes transformation between coordinate systems and establishes the mathematical model of permanent magnet synchronous motor in those coordinate systems.Analyzing the mathematical model of permanent magnet synchronous motor,this paper reseaches on simulation of PMSM DTC.After analyzing modules in direct torque control system,with large capacity and large inertia marine permanent magnet synchronous motor as the research object,this paper sets up simulation of its direct torque control system under MATLAB,and analysises the simulation under various working conditions.Aiming at the problem of big torque ripple in direct torque control system,after analyzing zero voltage can maintain electromagnetic torque,this paper divides torque error and flux linkage error reasonblely and introductes a fuzzy controller.Torque error and flux linkage error of direct torque control system is the inputs of the fuzzy controller,the fuzzy controler reasons the fuzzy inputs according to the defined fuzzy control rules.Fuzzy reasoning results combined with the stator flux in the sector selecte the most reasonable voltage vector.Research shows that the introduction of the fuzzy controller can effectively reduce the torque ripple.According to an electric propulsion ship,this paper builds the simulation model of its electric propulsion system,then reseaches on DTC and fuzzy DTC system under direct start and grading start working conditions.The simulations show that the fuzzy DTC can reduce torque ripple in electric propulsion system.