Modeling And Control Of Ships Shaft Brushless Double-Fed Machine Under PTO/PTI Mode

Brushless Doubly-fed Machine(BDFM),as a new type of AC excitation induction motor,,has the advantages of high reliability,easy maintenance and long life,because of eliminated the Brush and Slip Ring structure.It can be both used as a generator for variable speed constant frequency and constant voltage fields and as an electric motor for variable speed drive systems.Therefore,when it is used as a ship shaft motor,it can work in both PTO mode and PTI mode,which is the best choice for marine shaft belt system.The main reason why BDFM are not widely used today is that,besides their own structural design is not yet particularly mature,there are also problems with the practicality of various advanced control strategies.Therefore,the study of the control-side strategy of BDFM can provide a theoretical basis for its wide application and is of great significance to the shipbuilding industry.The BDFM is the research object,and the integrated control strategy and the direct torque control strategy based on SVPWM are proposed for the PTO and PTI operating modes respectively.And established the simulation mode in Simulink,the simulation experiments under different working conditions are performedto verify the control effect of the proposed control strategy.First,the prototype and development of the BDFM are introduced and the structure of the stator and rotor is analyzed,then the operating mechanism and the relationship of energy flow at different rotating speeds in the state of power generation and in the electric state are studied.The dynamic mathematical model of the BDFM in three-phase stationary coordinate system is established.Based on this,the mathematical model of BDFM in two-phase rotating dq coordinate system and rotor speed coordinate system is obtained by using coordinate transformation.The basic principle of double PWM frequency converter is studied.The principle of unit power factor control and energy bidirectional flow of PW side converter is studied.Then the mathematical model of PW side converter in three-phase stationary coordinate system is deduced.Then,aiming at the requirements and characteristics of the ship shaft BDFM independent power generation system in PTO mode,the vector control strategy of the traditional power winding flux linkage or voltage orientation is discarded,and an integrated control strategy,which is more suitable for an independent power generation system is proposed.For CW side converters,study and design the CW current vector decoupling control loop is designed,and the PW voltage amplitude control loop with feedforward compensation and the PW voltage frequency control loop is also designed.Finally,the complete control strategy of the CW side converter is given.For CW side converters,the current inner loop controller and voltage outer loop controller based on PW voltage orientation are designed.Finally,the complete PW side converter control strategy is given.The correctness and effectiveness of the comprehensive control strategy are proved through the simulation experiment under different working conditions.Finally,based on the detailed explanation of the principle of the PTI operation mode,against the torque and flux linkage pulsation is bigger and the inverter switch is not fixed in traditional direct torque control system,using the target voltage vector and SVPWM module to instand of the hysteresis comparator and switching voltage vector table,designing a BDFM direct torque control system based on SVPWM.The simulation results show that the BDFM direct torque control system based on the SVPWM can effectively reduce the pulsation of torque and flux linkage.