Designing for Large-Displacement Stability in Aircraft Power Systems

Due to the instabilities that may occur in power systems with regulated loads such as those used in military aircraft, ships, and terrestrial vehicles, many analysis techniques and design methodologies have been developed to ensure stable operation for expected operating conditions. However, many of these techniques are difficult to apply to complex systems and do not guarantee large-displacement stability following major disturbances such as faults, regenerative operation, large pulsed loads, and/or the loss of generating capacity. In this paper, a design paradigm is set forth guaranteeing large-displacement stability of a power system containing a significant penetration of regulated (constant-power) loads for any value of load power up to and including the steady-state rating of the source. Initial investigations are performed using an idealized model of a dc-source to determine the minimum requirements that ensure large-displacement stability. These investigations illustrate that a three-way tradeoff exists between the responsiveness of the source, its transient overload capacity, and the dc-bus capacitance. These results are then extended to a detailed design of a permanent-magnet generator/ rectifier source that is large-displacement stable for bounded changes in load power. Formulating the design as an evolutionary optimization problem, the response of system may be improved without compromising stability.