Research On The Control Of Doubly Fed DC Generation System In Stand-alone Operation

Under the background of energy shortage and environmental protection,ships are powered by shaft generators,which is an important means to improve the energy efficiency of ships and reduce shipping costs.As an important development direction of shaft generators,doubly-fed shaft DC generators have received extensive attention.The stand-alone doubly fed induction denerator for DC generation system is easily affected by changes in ship load and ship main engine speed.At the same time,due to the diode rectifier in the doubly-fed shaft DC generation system,it is easy to cause distortion of the stator voltage and current,resulting in large rotation torque pulsation affects the service life of the motor.Therefore,this paper takes the doubly-fed DC power generation system as a research object to design a controller to enhance its anti-interference ability,reduce current harmonics,weaken the motor torque ripple,and improve the overall operating performance.First,the value and significance of the independent operation of the doubly-fed DC power generation system applied to the ship's shaft power generation system are introduced.The mathematical model of the feeder in three-phase stationary coordinate system and two-phase rotating coordinate system.Secondly,the stand-alone control structure of the doubly-fed DC generation system is designed based on the principle of sliding mode control.Considering the influence of model uncertainty in the doubly-fed DC power generation system operating independently,a disturbance observer is designed to compensate,and a sliding mode DC voltage and rotor current controller is designed to enhance the robustness to load disturbances.The designed controller is applied to the independent running double-fed DC power generation system,and the DC voltage control performance of the PI controller is simulated and compared to verify the effectiveness of the designed controller.Finally,by analyzing the influence of the uncontrollable rectifier on the stator rotor current,voltage and torque ripple in the doubly-fed DC power generation system,focusing on the influence of the 5th and 7th harmonics in the stator current,a direct resonance controller is designed to compensate Hannonic voltage to reduce stator current harmonics and weaken motor torque ripple.It can be seen from the simulation results that the designed direct resonance controller can effectively reduce the 5 th and 7th harmonics in the stator current,and the torque ripple suppression effect is obvious.