Research On Madeling And Control Of Shaft Generator System Based On Dual-PWM Converters

At present,fossil fuel resources are becoming tense,oil prices are rising steadily,and the cost of ship operations continues to increase.At the same time,environmental protection issues are also becoming increasingly prominent.Ship energy conservation and emission reduction have become an inevitable trend for the development of the ship industry.Shaft generator system can reduce fuel consumption,reduce operating costs and pollution to the environment,and improve the working environment of the ship's engine room.Therefore,the shaft power system has been widely used on ships and has a high research value.Shaft generator system based on dual-PWM converters has the advantages of simple system structure,high output power quality,good control flexibility,large adaptability of main engine speed range,and the advantages of propulsion mode,becoming a new generation of high-tech development of the shaft generator system.In this thesis,starting from the components of the dual-PWM shaft generator system,the PWM rectifier system,the PWM inverter system and the PWM inverter grid-connected system are studied in depth,the corresponding mathematical model is established,the corresponding control scheme is studied,and the controller is designed,and through simulation experiments to verify.(1)Introduces the components of the dual-PWM shaft generator system,establishes the excitation system model of the shaft-synched generator and the diesel generator set speed control system.(2)Introduces the topological structure and working principle of PWM rectifier,deduces its mathematical model in two-phase synchronous rotating coordinate system,introduces the space vector pulse width modulation technology(SVPWM),and analyzes the control strategy of three-phase PWM rectifier.This thesis designed a voltage and current double closed-loop control system to improve the shortcomings of traditional voltage and current dual closed-loop control system parameters.Finally,the static and dynamic performance of the improved front-rear control system was compared through simulation experiments.(3)This thesis established the mathematical model of three-phase PWM inverter,proposes a feedforward decoupling control strategy for the problem of the coupling of control quantity,analyzes the principle of feedforward decoupling control,and designs a voltage and current double closed loop control system,and Analyzed the stability of the control system.(4)This thesis analyzes the basic principle of droop control,establishes a droop control mathematical model based on dynamic vector,and analyzes the stability of active power-frequency droop control system and reactive power-amplitude droop control system.Aiming at the shortcomings of traditional droop control,such as poor dynamic performance and static error,and proposed an improved strategy to add integral and differential links.Finally,the dynamic and static performance of front and rear droop control systems were improved through simulation experiments.(5)Based on the study of the various parts of the dual-PWM shaft generator system,this thesis combines the various parts into a dual-PWM shaft generator system,and builds a simulation model on the simulation platform,aiming at the integration of the shaft generator system in ship navigation,the three most common operating conditions,grid-connected operation and independent operation,were simulated and analyzed the simulation results.