On the Synchronous Reference Frame Impedance and Stability Characteristics of More Electric Aircraft Electrical Power Distribution Systems

In modern aviation electrical power distribution system (EPDS), power electronics converters (PECs) are gaining more prominence, providing a fully-controlled interface between different electrical equipment. In the context of utility ac electrical power systems, impedance-based stability analysis under Synchronous Reference Frame (SRF) has been established as a powerful tool to evaluate system stability and optimize system design. However, the SRF impedance characteristics of different kinds of PECs under high/variable fundamental frequency have not been addressed sufficiently. In this paper, an aircraft ground powering system consisting of an electrical ground power unit (eGPU) and an active front-end converter is selected as an illustrative example to give a comprehensive analysis of the impedance characteristics of such system. A comparison is made between the impedance measurement results of the hardware-in-the-loop setup and a lab-scale (0.1 p. u.) experimental setup, as well as the analytical model. On this basis, the stability of the EPDS is investigated by frequency domain analysis and experiment with variable fundamental frequency. The results highlight that variable fundamental frequency significantly reshapes the SRF impedance characteristics of PECs, influencing the system stability margin. The procedure of stability assessment presented in this work provides a future reference for designing PEC-dominated EPDS with variable fundamental frequency.