The Research Of Control System Of Permanent Magnetic Synchronous Motors Applied In Ship Electric Propulsion

In the near decades, with the rapid development of power electronic elements, high power converters as well as the advent of poded propulsion systems, ship electric propulsion has gradually become the main steam of future ships with several advantages such as higher flexibility of space arrangement, better maneuverability, higher driving efficiency and reduced fuel consumption.The research background in this paper was based on some domestic electric ship. Firstly, the characteristics of thrust force and torque of poded propellers were analyzed, as well as the resistive characteristics of electric ship. Mathematical models and SIMULINK models were then established and treated as the main load of the whole system. A permanent magnetic synchronous motor (PMSM) was chosen as the driving motor of the system and hence the direct study object because of its excellent performance in variable speed of high power system. After that, mathematical models of a PMSM in different coordinate systems were analyzed here, as well as the basic principle and the implement method of direct torque control (DTC). And then, a stator linkage observer which is based on the PID adaptive close-loop compensate method was also presented in order to effectively restrain the impact of observing linkage caused by DC offset.Three-level strategy was introduced here in order to cope with the problems of high torque ripple encountered in the traditional DTC systems. Firstly, the basic principle of diode- clamped three-level inverter was given and the special problems aroused by DTC technique when it was applied in variable speed systems were also discussed. A simple feasible voltage vector selection scheme was provided in order to solve the problems of neutral voltage balance and restriction of voltage limitations and get a better control over them. At the end of the paper, the propeller model, the ship model and the three-level DTC model of PMSM were integrated. The whole simulation model of ship electric propulsion system based on three-level DTC technique was then established in the SIMULINK environment. Benefiting from the successful experiences of the Marine Automation and Simulator Research Institute of DMU, the author developed a distributed simulation system of ship electric propulsion system in VC++ environment. The comparisons of the results show that the three-level DTC has a better dynamic and static performance than traditional two-level DTC and hence validate the presented scheme.