An auxiliary power unit for advanced aircraft electric power systems

• A study model is developed for aircraft electric power systems.
• A hybrid back-up system is proposed for reliable operation.
• The system's dynamics are characterized under various conditions.
• The obtained results are validated with the applicable aircraft standards.
• The simulation results are verified using a bench model.

This article presents a comprehensive model and characterization of the Advanced Aircraft Electric Power Systems (AAEPS) with a hybrid Fuel Cell (FC)/battery Auxiliary Power Unit (APU). A model of fully controlled AAEPS for Boeing 767 is implemented in PSIM9 software environment. Also, a circuit model representation of the hybrid Proton Exchange Membrane (PEM) FC/battery APU is developed and integrated into the main power channel of a Variable Speed Constant Frequency (VSCF) aircraft electric power system at the main DC bus. The transient performance of the interconnected electric power system is studied under a large share of nonlinear loads. Moreover, the fuel cell based APU integrated model is extended to investigate the dynamic behavior of the AAEPS under various loading configurations. The entire system's stability is analyzed while different loading scenarios are taken into account. Several case studies are performed in order to measure the effectiveness and applicability of the proposed hybrid APU in an advanced aircraft operation. The time-domain analysis corresponding to each study is performed. Also, the obtained voltage and current data are validated using applicable aircraft electric power system's standards [20]. Finally, a bench model is developed for the hybrid APU to verify the simulation results from PSIM9 model.