Rotor Position Estimation Of Three Stage Starter/Generator Based On The Main Machine Injection And The Exciter Detection

Accurate rotor position of the Main Machine(MM)is required during the start process of the three stage brushless synchronous starter/generator(TSBSSG).Due to the extremely strict limitation of the electromagnetic,the space environment and the installation conditions,the usage of traditional position sensors has to overcome these issues in reality.Thus,it's of utmost importance to study the rotor position estimation technology for the three stage motor without the requirement of the position sensor.The MM needs to provide large torque to meet the demand of the aero engine,when the TSBSSG is still or in low speed region.Meanwhile,the saliency of MM is varied because of the saturation effect and the cross saturation effect.Therefore,the accuracy of the rotor position estimation methods based on tracking the saliency is significantly decreased when the saliency of the MM gradually becomes lower or disappeared.In this condition,the TSBSSG cannot start with sensorless control methods.In order to estimate the rotor position when the saliency of the MM is lower or disappeared,this paper proposes a rotor position estimation method based on MM injection and Main Exciter(ME)detection.Utilizing the feature of TSBSSG structure,the proposed method injects high frequency signals into the stator of the MM.The responses are then obtained from the stator of ME to estimate the rotor position of the MM.Based on the “MM injection-ME detection” method,the key technologies of rotor position estimation considering the variation of the saliency for TSBSSG are studied in this paper.The main research topics includes the discipline for the change of the saliency in MM,estimation of the initial rotor position e in MM,and the rotor position estimation regarding to the gradually decrease and disappear of the saliency in MM.Firstly,the regular pattern of the changes in the saliency of MM during the start process of the TSBSSG is studied.After analyzing the operating states of the MM and ME during the starting process,the variation ranges of the armature current and the excitation current of MM are obtained.In addition,the variation of the d-axis and q-axis inductance under those current are calculated.By analyzing the variation of the d-axis and q-axis inductance,the variation and vanishing curves of the saliency in MM are obtained considering different excitation current.Hence,the phenomenon including the decrease,disappear and reverse of the saliency in the MM during the start process are found.Secondly,the methods for estimating the initial rotor position of the TSBSSG are studied.According to vanishing curves of the saliency in MM,the saliency of MM can be reversed by increasing the value of the excitation current and the armature current.After injecting high frequency current,the initial rotor position of MM can be then estimated under the condition that the saliency is reversed.When the load is light,traditional voltage signal injection method is used to detect the rotor position of the MM by tracking the saliency of the MM.The traditional method can estimate accurate position at light load condition.However,with the increase of the torque form the load,the large excitation current and the armature current lead to the saturation of the magnetic field in the MM.Since the saliency is decreased causing by the saturation in the magnetic field,traditional methods are not able to estimate rotor position with high accuracy under this condition.Thirdly,a rotor position estimation method based on MM injection and ME detection is proposed.The proposed method establishes a high frequency signal transmission pathway in the rotating components of the TSBSSG.Thus,the transmission mechanism of the high frequency signal in the MM,rotating rectifier and ME are studied based on the proposed pathway.The switching state of the diode in the rotating rectifier during the rectification process are detailed in this paper.Afterwards,the reverse transfer model of the high frequency signal is established,in order to obtain the mathematic model of the valid high frequency signal in the stator of the ME.The proposed rotor position estimation method based on MM injection and ME detection does not rely on the saliency of the electrical machine.It is able to estimate accurate rotor position of the MM even when the saliency of the MM is disappeared.Fourthly,a rotor position extraction method is proposed based on MM injection and ME detection.In order to extract the rotor position from the stator of ME,the starting state of the TSBSSG is analyzed in this paper.The amplitude and frequency of the high frequency signal are selected.Afterwards,the valid high frequency signal extraction method and the filtering algorithm are optimized to improve the dynamic performance of the rotor position estimation method.The test bench for the TSBSSG are established in this paper so that the methods for the rotor position estimation of the TSBSSG can be validated.After comparing the traditional rotor detection methods based on tracking the saliency with the proposed method in dynamic and steady state performance,the effectiveness of the proposed rotor detection method based on MM injection and ME detection considering also the variation of the saliency in MM is proved.