Research On The Starting/Generating Integration System Of Small And Medium-power Aircraft

With the development of aircraft technology,the aircrafts tend to be lightweight and high-power,and the demand for electric energy is gradually increasing.The starting/generating integrated technology eliminates the starting devices and reduces the volume of aircraf,and it can provide high-power power for the aircraft to ensure the power supply safety.In this paper,the starting/generating integration system on medium and small power aircraft is taken as the research object.The integrated starter generator,the control strategy of starting and generating conditions,the dynamic characteristics of starting/generating switching process and the influence of the parameters of starting/generating system on the control performance are studied.According to the operation principle of the permanent magnet synchronous integrated starter generator and the technical index of the starting/generating system of the aircraft,the key problems in the design process of the integrated starter generator are analyzed,such as the output voltage requirement under the minimum generating speed,the torque performance and the field weakening performance.The difficulties and contradictions in the electromagnetic design of the integrated starter generator are obtained.The influence of different rotor structures on the inductance performance of the integrated starter generator is studied by two-dimensional finite element calculation,and the optimal rotor structure is obtained.A design process of integrated starter generator is proposed,which can balance the contradiction between the starting condition and the generating condition.The simulation of the designed 20 k W integrated starter generator through two-dimensional finite element calculation verifies the power generation performance and electric performance.Based on the field oriented control(FOC)technique,the maximum torque current ratio(MTPA)control strategy under the electric condition and the voltage stabilization field weakening control strategy under the power generation condition are designed.By using the simulation software,the characteristics of the starting condition and the generating condition are simulated and analyzed.It is verified that the designed integrated starter generator and the control strategy accord with the operation condition of the starting/generating system of the aircraft.The experiment platform of starting/generating system is set up to verify the feasibility of permanent magnet synchronous machine as integrated starter generator.Aiming at the problem of the integration of starting/generating system,two kinds of integrated circuits,dual-channel structure and single-channel structure,are proposed.The single-channel circuit is smaller in volume and lower in cost,which has great advantages in the aircraft.The transient process of starting/generating switch of single channel circuit is analyzed,and there are three stages in the process of switching: electric exit,power generation build voltage and stable voltage regulation.Aiming at the problem that the output voltage overshoot is too high in the switching process of single-channel system,the control strategy of voltage step modulation is proposed,and the switching effect is improved obviously.A system experiment platform of starting/generating switch process is built to verify the dynamic characteristics.In view of the problems of magnetic saturation and harmonic back EMF of the integrated starter generator,the influence of magnetic saturation and harmonic back EMF on the field weakening performance of starting/generating system is analyzed.The influence of magnetic saturation on the inductance and the harmonic back EMF on the field weakening performance of the generator is obtained by using two-dimensional finite element calculation.Based on the field-circuit simulation platform,the field-circuit analysis of the starting condition and the generating condition is carried out considering the phenomena of the harmonics back EMF and magnetic saturation.The results show that the system operating current increases obviously,the electromagnetic torque decreases,the speed range of field weakening voltage stabilizes decreases,and the control performance of the starting/generating system becomes worse than that the theory.