Research On Position Sensorless Control For Doubly Salient Electro-Magnetic Mahcine

With the development of more electric aircraft(MEA),aero starter generator(SG)technology has become the key of aviation power system.As a novel kind of brushless dc machine,there is no permanent magnet or windings mounted on the rotor of doubly salient electro-magnetic machine(DSEM),enhancing its operation ability under high temperature and high speed conditions.And in addition,it owns the advantage of high control flexibility and stong fault tolerance,since the generating voltage can be directly controlled by the field current,and the field current can be removed for field suppression.So DSEM is able to become a competitive candidate for aero SG.Accurate rotor position is essential for the commutation when DSEM operates under starting mode as well as the speed estimation when DSEM operates under generating mode.However,in traditional DSEM driving system,the installation of mechanical position sensor not only causes the oversize problem and reduced reliability,but also raises the production cost.In face of these disadvantages,position sensorless control for DSEM is of great research signifance.This thesis focuees on the position sensorless control techniques over full speed range when DSEM operates under starting mode.By combining theoretical analysis,digital simulation and experimental verification,this thesis mainly studies the initial rotor position estimation and anti-reverse startup method,position sensorles startup techniques at low speed,the control methods enchancing motor sensorless startup performance,position sesnorless and advanced angle control strategies of DSEM at medium and high speeds.Initial rotor position estimation is the basis of motor position sensorless control.According to the varying feature of DSEM self-inductance with rotor position,this thesis first proposes an initial rotor position estimation method based on test pulse injection,and the width of test pulse is analyzed as well.Then,considering that DSEM is a kind of electric excitation motor,a novel initial rotor position estimation technology during field building process is put forward,in which rotor angular position is estimated based on the geometrical similar relation in the curves of mutual inductances between armature windings and field winding.After that,boundary sector of DSEM is proposed,the first acceleration pulse is distinguished from ordinary ones,and the selection strategy of the first acceleration pulse is investigated to avoid the occurance of reverse.Position sesnorless startup at low speed has always been the difficult point of motor sensorless operation.To realize the sensorless startup of DSEM,this thesis firstly studies the application of “align and go” for DSEM sensorless startup,the alignment process is theoritically analyzed,and a simplified method of “align and go” is developed for DSEM.Then,in view of the varying characteristic of DSEM self-inductance,this thesis mainly focuses on the position sensorless startup techniques based on pulse injection.Three kinds of DSEM position startup methods are proposed:(i)based on the comparision of two-phase series inductances,(ii)based on the comparision of current conduction phase series inductance and commutation conduction phase series inductance,(iii)based on the comparision of two proper phase inductances.What's more,the proposed three sensorless startup methods are comparative studied in terms of rotor position estimation accuracy,output torque and robustness.Under the conventional startup methods based on pulse injection,there is inebitale commutation lag in the startup process since rotor sector is estimated only once in a pulse injection cycle.To overcome this problem,a novel rotor angular position estimation method for DSEM startup is put forward based on the geometrical similar relation in the curves of self-inductances.In addition,the estimation error caused by non-ideal linearity of self-inductance is theoritically analyzed,and a compensation strategy based on boubdary sector is proposed.In further,to enhance the startup performance,the output torque of test pulses are studied,and a novel optimized selection strategy of test pulses is developed.When startup is fulfilled,DSEM will operates at medium and high speeds for a long time,so the sensorless control at this speed range is very essential.According to the varying feature of back electromotive force(EMF),a novel sensorless control method based on idle phase voletage is proposed for medium and high speeds,and in addition,the implementation of advanced angle control(AAC)under this sensorless control mode is studied.Then,in consideration of the best advanced commutation angle is very hard to be callulated accurately in actual system,this thesis proposes a novel self-optimizing control strategy of advanced commutation angle,the output torque performance as well as system efficiency are desired to be enhanced.Finally,due to the unavailability to neutral point in general motor,this thesis proposes a rotor position estimation strategy based on line-to-line voltage,and a uniform compensation strategy is investigated to compensate the commutation errors caused by reluctance back EMF and low-pass filter.The aforementioned technologies are experimentally verified on a three-phase 12/8-pole DSEM experimental setup,in which RT-LAB serves as the real-time controller.They lay a theoretical and technical foundation for the sensorless control of DSEM in aviation power system.