Research On Transient Stability Of Independent Power Generation System With Ship Shaft With BDFG

Marine transportation is a major energy consumer.Under the trend of energy conservation and emission reduction,in order to improve the economic and environmental protection of the modern ship transportation industry,the research and application of BDFG power generation technology in the marine shaft system has been widely concerned.However,the control strategy of the power generation system is still the main factor restricting the development of the technology at present.When the ship speed regulation and switching large power loads,the transient stability of the independent power generation system is greatly affected.Even when the short circuit occurs,the system equipment will be damaged.Therefore,the thesis took the marine shaft with BDFG independent power generation system as the research object,based on the transient model,carried out the comprehensive control strategy for the independent power generation system,and deeply studies the transient characteristics and transient stability of the system.Finally,a systematic study on the transient process of short circuit was made.At the same time,the Matlab/Simulink platform was used to simulate the theory.Firstly,the principle of power generation of the BDFG variable speed constant frequency was clarified through the derivation of the internal stator magnetomotive force and rotor magnetomotive force of the BDFG.The complex electromagnetic relationmarine inside the motor was sorted out,and the unified equivalent circuit of the motor was obtained through winding conversion and frequency conversion were utilized.On this basis,the dynamic mathematical model of the BDFG in the three-phase stationary coordinate system and the two-phase rotating coordinate system was established.Secondly,the scalar control was established for the independent power generation system of the marine shaft with BDFG,which corrected the model was verified by simulation.And it was found the power consumption transient fluctuation is large under the scalar control.Therefore,in order to solve this problem,an integrated control strategy was proposed,which was more suitable for independent power generation system.For the control winding side converter,the current vector decoupling control loop and the power winding voltage amplitude and frequency control loop with feedforward compensation were designed.The DC-side bus voltage outer loop and current inner loop controller were designed in the grid-side converter.The simulation showed that the transient fluctuation and dynamic response speed of the system had been improved under the control strategy.Then,through qualitative analysis,the transient behavior and transient characteristics of the system were clarified when the marine changes speed and adjusts the loads.For the speed regulation condition,in order to study the electromechanical coupling relationmarine of the system,which transient power angle was construct through quantitative analysis.For the loads-carrying condition,the transient drop expression of the terminal voltage was derived and analyzed.When the transient drop problem was proposed,a control method was proposed,which was based on the compensation of the steady-state component of the reactive current.The transient control effect was compared under the reactive current full compensation and half compensation.Finally,for the three-phase short-circuit fault condition of the BDFG,the transient current expression of each winding in the fault was derived according to the flux-conservation.By analyzing the short-circuit process and the transient electromagnetic quantity,the protection circuit design was proposed to add Crowbar resistance on the CW side and the resistor on the DC bus side.And the transient current expression was derived after adding the protection circuit.And it was verified to carry out simulation experiments.