Research On Sensorless Control Of Brushless Synchronous Machines At Starting Stage

More electric aircraft has eventually become the development trend of aircraft technology,and aircraft power supply technology is a key point of the more electric aircraft technology.As regards to large civil aircrafts,variable frequency AC power system is the trend of their supply systems,and integrated starter and generator based on brushless synchronous machine is a crucial technology of it.The realization of integrated starter and generator's starting function depends on the extraction of rotor position by position sensor.However,the accuracy and reliability of mechanical position sensor are influenced by environment,especially on aircraft.To solve these problems,sensorless control technology of brushless synchronous machines is born and becomes important research contents of integrated brushless synchronous starter and generator technology.This paper also studies sensorless control technology of brushless synchronous machines at starting stage,and it has important theoretical significance and practical value.Firstly,Structure and mathematical model of brushless synchronous machine are introduced.Based on this,a novel high-frequency signal injection sensorless control method by main exciters,which is aimed at low-speed stage,is proposed.Rotating high-frequency signals are injected into main exciter in the process of three-phase AC excitation.And then,high-frequency signal is coupled into field winding of main generator through rotor winding of main exciter and rotating rectifier.Besides,influences of rectifier and speed on high-frequency signal are researched in this paper.Also,a nonsynchronous extraction method of rotor position information and a detection method of initial position are proposed.Secondly,Back EMF sensorless control method based on phase locked loop at medium-and-high-speed stage is presented,and these two methods are combined with the switch strategy to realize sensorless control of brushless synchronous machines at whole starting stage.On the base of theoretical research,the model of brushless synchronous machine's sensorless starting control system is established by MATLAB and simulation analysis is completed.Finally,the platform of brushless synchronous machine sensorless starting control system is built with DSP and CPLD as its control core,and the control programs are written for the hardware.Also,the experiments are completed.The good accuracy of rotor position estimation is validated by the experiment results,and sensorless starting control of the brushless synchronous machine is implemented.