Research On Sensorless DTC In Ship Electric Propulsion System

In recent decades, with the development of power electronic and the increasingly maturation of large-power AC motor variable frequency speed control technology, the ship electric propulsion technology shows its advantages in civil and military ship little by little and becomes the development trend of future ship power plant. Based on DSP technology, digital controlled electric propulsion ship will have a wide foreground, which uses Permanent Magnet Synchronous Motors (PMSM) as power units and adopts high quality control strategy, such as the Field Oriented Control (FOC), Direct Torque Control (DTC), Sensorless and so on. At present, the research of ship electric propulsion technology is still at the starting stage in China. Therefore, modeling and simulation have important practical significance for the theory research and production development of ship electric propulsion technology.First of all, the structure of electric propulsion system is introduced and the advantage and disadvantage compared with general propulsion is analyzed in this paper. Then, the propeller thrust and the torque dimensionless coefficient curve fitting were studied and the hull-propeller model was established. Secondly, the principle of DTC is introduced. Aiming at the problems of DTC, such as inconstant inverter switching frequency and large torque ripple, a novel DTC strategy of PMSM is adopted by using observing error of stator flux linkage. It is based on the principle of FOC, which can realize continuous voltage vector modulation. The simulation results indicate that the scheme has better torque dynamic performance and can decrease the torque ripple effectively. So, it improves the system control performance greatly. Thirdly, the Motor basic equation method and the Model Reference Adaptive method of speed identification were simulated in this paper. A mix algorithm is put forward in this paper after analyzing the characteristic of the above two method for speed identification. The simulation results prove that the mix algorithm has good dynamic and steady performance at the same time. In the end, the ship integrated electric propulsion simulation system was established and simulated by united the hull-propeller model and the propulsion motor control model and the dynamic accelerating process of the ship from the static to the full speed and the three-level starting was simulated.Some exploring research on ship electric propulsion system taking the PMSM as the propulsion motor has been developed in this paper. Some significant conclusions have been drawn by academic analysis and simulation. This paper is the base of further research for the subject.