Study of Starting Performance of a Series Hybrid Aero Propulsion System

Combined with the development trend of high speed generators and the high voltage of DC microgrids in high-power series hybrid aero propulsion system, a set of hybrid systems with a power of 200 kW, voltage of 540 V, and speed of 21,000 r/min is established in this article. Ground starting tests were conducted, focusing on the analysis of the coupling characteristics between the engine, generator and motors/propellers during the starting process, and further facilitated the optimization of the strategy of starting control. Firstly, the starting process of the series hybrid aero propulsion system mainly consists of four stages: the turboshaft engine is started, the gas turbine speed is increased, the controlled rectification intervenes, and the electric propeller is activated. The recommended definition of the idle state of the 200 kW hybrid propulsion system in this paper is as follows: power turbine speed NP = 10,500 rpm, grid system voltage UDC = 540 V, and the minimum stable power state of the electric motor PM = 150 W. Furthermore, experiments reveal that during the starting process, the resistance value and the rectification strategy, respectively, affect the steady-state and dynamic characteristics of the power turbine speed. By comparing multiple sets of experiments and utilizing data fitting software for optimal design, the results indicate that, based on the starting strategy of no-load protection and two-step controlled rectification, the total duration of the optimized starting process is shortened by 64.7%, and the gas turbine speed is reduced by 22.7% compared to the pre-optimized state. The starting control sequence is clearer, and the optimization effect is significant.