Optimization Research On Starting Characteristics And Start-up Mode Of High Voltage And Large Capacity Synchronous Motors

The synchronous motor is widely used in industrial production,due to its adjustable power factor,the fixed speed is not affected by the load.However,because the capacity is so large,it becomes a problem to be solved,that it is difficult to start.During the starting process of synchronous motor,the impact current will be 4-7 times higher than the rated current of the motor.This will affect the system transmission and distribution of lines and buses at all levels.The voltage drop will make the electrical equipment run abnormally,and even interfere with the stable operation of the whole power system.Therefore,it is of great significance to study the optimization of starting characteristics and start-up mode of large capacity synchronous motor.Firstly,this thesis the structure and working principle,which elaborates the interaction between the current in the stator winding and the rotor magnetic field,and then analysis two kinds of electromagnetic torques between the stator winding and the permanent magnet and the salient pole rotor.A mathematical model of permanent magnet synchronous motor(PMSM)in three-phase stationary coordinate system and dq coordinate system is estabilished.By studies the operating characteristics of synchronous motor,the influence of power-torque,torque-speed and load and excitation current is obtained.Secondly,analysis two mehtods of full pressure and Step-down start,Huangjinxia Pumping Station(18.5MW,13.5kV)in Shanxi Province as the object of study,on the basis of the engineering background,the main bus connection of the pump station,system parameters and operational specification,can be obtained that the full pressure start does not meet the start requirements,then the software ETAP is used to simulate,verifies the infeasibility of full pressure and step-down start.Thirdly,the static frequency conversion start is mainly studied,including rotor position detection,thyristor switching,next,according to the current type AC-DC-AC dirve start program,a simulation model of the entire starting system,using Matlab/Simulink,aiming at the situation that the stator voltage of the stator terminal is relatively high at the beginning of the initial stage,the low-pass filter circuit is designed to provide accurate protection for the rotor position,using constant voltage ratio control strategy,through the real-time simulation of the whole starting process of synchronous motor,the static frequency conversion to start the bus at all levels and the pressure drop of each node meet the requirements of the specification,the impact of the grid is small,the start process is gentle,to meet the start requirements,providing basis for static frequencyconversion.By comparing the two simulation results,it is concluded that the frequency conversion is the best way to guide the operation of the synchronous motor.Finally,this thesis summarizes the research and presents prospects for the study of large capacity synchronous motor starting process and the various ways to start the distribution system for reference.