Research On Direct Torque Control Of Permanent Magnet Synchronous Motor In Pod Propulsion

Pod propulsion is a new sort of electric propulsion. International shipbuilding and shipping group has attached great importance to this mode. Only in recent years , the research about pod propulsion is developed in China. But we have made some progress and we assure that pod propulsion has a wide foreground. In this paper, the structure of pod electric propulsion system is introduced, the advantage and disadvantage compared with general propulsion is analyzed, the math model of ship, propeller and machine is set up and analyze the interaction among the three parts considering the influence of pod. Pod electric propulsion system driven by permanent magnet synchronous motors (PMSM) is also simulated by computer.Compared general motor, PMSM is smaller, lighter and more efficient, so it's suitable for pod electric propulsion system. At present, with the development of permanent magnet material, PMSM has been a normal configuration for new pod thrusters. In the past, vector control(VC) method is usually applied in PMSM drive systems. But the arithmetic of VC is too complex, and the control performance is easily affected by parameters. Direct torque control(DTC) is a new kind of AC timing method after VC. DTC has simple structure and fast torque response. It has been applied in various fields. It is also introduced in some pod propulsion systems recently. In this paper, the principle of DTC is introduced, some elementary problems of PMSM DTC is also analyzed. Excursion of stator flux and the compensatory method is introduced. The function and configuration of sub-models of PMSM DTC system is discussed, the scheme of this system is brought forward, and the simulating model based on Matlab/simulink is set up. The results of simulation validate the feasibility of this system. At last, the problem of PMSM drive system without mechanical sensor is discussed. A sensorless method based on stator flux is presented, and the result of this method is simulated by computer, the result is very accurate to some extent.