| At present,energy problems are becoming more and more serious,and energy conservation and emission reduction is an inevitable choice for society.Because the ship uses a shaft generator,it improves the economy of ship shipping,and reduces carbon emissions,so it is more green and environmentally friendly,and the working environment is also improved.Therefore,the shaft power generation system has been widely used in ships,and has high research value and application prospects.The ship permanent magnet shaft power generation system adopts the permanent magnet synchronous generator as the shaft generator,which has the advantages of simple structure,high safety and high efficiency.It is a new trend in the research and development of the ship shaft power generation system.The research object of this thesis is the shaft power generation system using the permanent magnet synchronous generator as the shaft generator.Taking the shaft power generation system as the control object,the control strategy is designed and researched to realize the shaft power generation system between the speed of the main engine of the ship and the speed of the ship.When the load changes,the voltage at the output terminal remains stable;when the operating mode of the shaft power generation system is switched,the control strategy of the PWM inverter is designed to realize the smooth switching of the operating mode.The main research contents of this thesis are as follows:Firstly,the structure of the permanent magnet synchronous generator is studied,and its mathematical model in the three-phase static coordinate system is established.Based on this,the mathematical model in the coordinate system is derived through coordinate transformation;and then the PWM rectifier is established in the coordinate system.Enter the mathematical model below.In view of the coupling problem of the system shaft current in the voltage regulation control process of the shaft generator during variable speed operation,when controlling the PWM rectifier,a current feedforward decoupling control strategy is designed to realize the shaft current decoupling and maintain the rectifier side voltage at the PMSG Stability during variable speed operation.Finally,the designed control strategy is simulated in Matlab/Simulink,and the simulation results are analyzed.Secondly,the mathematical analysis of the PWM inverter in the shaft power generation system is carried out,and its mathematical model in the coordinate system is established.Based on the mathematical model of the PWM inverter,the control strategy of the PWM inverter for the ship’s shaft power generation system in the independent operation mode is designed to keep the output voltage and frequency of the shaft power generation system stable when it operates independently.At the same time,based on the PWM The mathematical model of the inverter is used to design the control strategy of the ship’s shaft power generation system when it works in gridconnected operation,so as to realize the stable grid-connected operation between it and the ship’s power grid composed of diesel generator sets and their control systems.Finally,in Matlab/Simulink,the control strategy of PWM inverter in independent operation and grid-connected operation is simulated and tested,and the test results are analyzed.Finally,the requirements for smooth switching of the operating mode of the shaft power generation system are introduced,and the reasons for the transient impact on the power grid when the traditional method is switched are analyzed.Aiming at the problem that the power grid is impacted by the switching of the control strategy when the operating mode of the shaft power generation system is switched,the traditional droop control strategy is introduced and improved,and a virtual switching technology based on the improved droop control strategy is designed to achieve smooth switching of operating modes..The designed control strategy is simulated and tested in Matlab/Simulink,and the test results are analyzed. |
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