Research On PTC Strategy Of Marine PMSM Based On Active Distobance Rejection Control

Electric propulsion has become a most promising ship propulsion mode due to its various advantages,while the best choice of propulsion motor for podded propulsor is almost permanent magnet synchronous motor(PMSM)currently.Because of simple structure and good dynamic performance,direct torque control(DTC)technology of PMSM is more suitable to apply in marine propulsion system compared with vector control.Therefore based on DTC theory,deep research of stator flux and speed estimation methods,torque and speed control strategies is done in this thesis,in which marine PMSM is chosen as the object.Also the process of simulation in Matlab/Simulink and corresponding analysis is shown.Fistly,DTC system is studied and its characteristics are anlyzed based on the mathematical model of PMSM.Then DTC technology is combined with space vector pulse width modulation(SVPWM)in order to accurately compensate stator flux and electromagnetic torque error.A torque regulator composed of predictive voltage calculation and SVPWM is designed.Simulation results indicate that stator flux and torque ripples are greatly reduced through SVPWM technology.Secondly,extended state observation(ESO)principle is studied and the mathematical model of PMSM in two-phase fixed reference frame is analyzed in detail.The ESO flux observer is designed to estimate the stator flux of the flux differential equation,and it serves as the stator flux signal.Also ESO speed observer is designed to estimate the speed of the current differential equation,and it serves as the motor speed feedback signal.Then stator flux and speed observers are applied in PMSM DTC system and simulation is carried out.Results show that stator flux can be estimated by ESO accurately and stably,which is not susceptible to the stator resistance changes.Meanwhile ESO speed observer has an identification of hig precision and good speed tracking effect.Thirdly,an improved motor speed control system is designed based on active disturbance rejection control(ADRC)principle and PMSM equation of rotor motion.The design process of ADRC speed regulator and the parameter tuning method is highlighted.Then various disturbances are simulated in PMSM operation conditions.Simulation results indicate that ADRC can eliminate the contradiction between fast response and overshoot,and suppress disturbances so as to improve the robustness of the control system.Lastly,the ship motion and propeller load charateristics are studied based on a parent ship named China Railway Bohai.Marine electric propulsion system is established with an improved DTC system containing ADRC speed regulator,ESO stator flux and speed observer and SVPWM technology.Several simulations such as motor starting,parameter perturbation,propeller blocked and out of water are carried out.Results indicate that the marine electric propulsion system with an improved DTC strategy can operate with no overshoot or little torque ripples,immune to various disturbances.Besides its speed signal is accurately observed which attributes to sensorless speed control.