Research On Key Technologies Of High-speed Doubly Salient Starter/Generator System For More Electric Engine Application

The more electric engine(MEE)is the core component of the more electric aircraft(MEA).The internal starter/generator system,charactered by the high-speed starter/generator technology and magnetic suspension technology,is a significant foundation for the MEE.The doubly salient electromagnetic machine(DSEM)featuring the advantages of robust and reliable structure and simple generation control has the important application value in the aircraft DC starter/generator system.Based on the significant demands and special requirements of the MEE,this dissertation aims at the basic scientific issues in terms of the structural stability design,high-efficiency optimization and control strategy of the high-speed doubly salient starter/generator used in a complicated application environment.The key technologies with respect to the topology evolutions,high-speed operation characteristics and design rules,starting control strategies,bearingless operation and high-speed experimental verifications are basically studied in this dissertation.The development trends of aircraft electrification and the characteristics of airborne secondary power are discussed.The basic concept of the MEE is expounded.In addition,according to the crucial requirements of the simplified gearbox and oil-free system of the MEE,two key technologies for the high-speed starter/generator technology and rotor suspension technology supporting the development of the MEE are analyzed.Furthermore,combined with the characteristics of the integrated installation position and operation environment in the MEE,the development status of switched reluctance starter/generator systems and permanent magnet starter/generator systems applied to the MEE is discussed in detail.Based on this,the application prospects and advantages of the high-speed doubly salient starter/generator employed in the MEE are further elaborated.Based on the stator field distribution and coil electromotive force phasor,the structural topologies of the DSEM-like machines suitable for the MEEs are studied and summarized,covering the topologies of different field pitches and non-uniform field pitches,revealing the topologically unified principle of the DSEM-like machines.In addition,under the condition of the internal high-speed operation,the performances of two types of the DSEMs with different field distributions and phase flux-linkage characteristics are studied.To be specific,the distributions and time-varying patterns of the magnetic flux in the cores are revealed by the flux phasor relationships.The influence of the relationship between the stator unit pole number and pole arc on the variations of the magnetic field is analyzed.At last,two high-speed DSEM-like machines are comparatively studies in terms of the loss characteristics of the cores and windings.Based on this,the theoretical foundations for the optimal designs of the high-power high-speed internal starter/generator are provided.Aiming at the high-speed operation characteristics of the MEE internal starter/generator,according to the iron core material characteristics utilized in the high-speed DSEM,the influence of the material preparation methods and lamination thickness on the mechanical properties and magnetic properties of the iron-cobalt-vanadium soft magnetic alloy are discussed and summarized.Combined with the application characteristics of the high-speed DSEM in the internal environment of the MEE,the variation characteristics of the core material in high-temperature and high-speed environment are illustrated.In addition,the structure size constraints of the high-speed DSEM considering the rotor core material performances are studied.Based on the study of the stress distributions and dynamic characteristics of the high-speed rotor,the optimal design methods are systematically proposed.And the effects of the high-speed operation conditions and material properties on the DSEM designs are described.Finally,the structural-paralleled prototype is developed and the experimental verifications are given.Aiming at the rotor suspension demands of the MEE,based on the air-gap field distribution characteristics of the DSEM,a new bearingless DSEM(BDSEM)is proposed and the principle of the suspension is expounded.To be specific,through the constructions of the mathematical model of suspension force,the relationship between the suspension force and rotor position and current is analyzed.In addition,the suspension control methods,suspension winding inductances and suspension force characteristics of the BDSEM and the bearingless switched reluctance machine are comparatively analyzed.At last,the prototype of the 12/8-pole BDSEM and its suspension controller are developed and the static suspension test results are given.The more electric integrated power unit(IPU)is an aircraft turboshaft MEE,which provides auxiliary and emergency power for airborne equipment.The appropriate basic structures of the more electric IPU are discussed and proposed.Focusing on the starting characteristics of the internal high-speed doubly salient starter/generator system of the more electric IPU,the varied-voltage DC bus for starting operation is proposed.Furthermore,based on the optimal efficiency and maximum torque per current respectively,the synergistic control methods of the field current and the advanced angle under different bus voltages are obtained,and the corresponding experiments are conducted.