Stability analysis of hybrid power systems for ‘more electric’ technologies

Electric systems in automotive, aerospace, marine and other sectors are continuously increasing in complexity and power levels as a result of the constant trend towards "more electric" vehicles in which an increasingly significant portion of the mechanical and hydraulic power required for propulsion, actuation and environmental control is being substituted by electric power, with expected benefits in terms of increased efficiency, reduced costs and environmental impact.

The increased complexity of the resulting electric power systems creates new challenges in terms of design optimization, system analysis and control. In particular, the interactions among several interconnected nonlinear loads and subsystems may give rise to complex dynamics, which can pose serious problems in power system analysis and integration for "more electric" vehicles. Stability problems caused by negative impedance behaviour resulting from constant power characteristic of tightly regulated power electronics loads not only constitute a potentially harmful threat to system operations, but also lead to demanding constraints on components/subsystems optimization in terms of sizing, weight and ultimately cost.

Analysis, design, validation and optimization of such complex electrical power systems have required the development of several analytical and numerical tools, some of them in collaboration with the German Aerospace Centre DLR.

Numerical simulations together with thorough analytical investigations have been carried out to determine key parameters influencing small and large signal stability boundaries of hybrid power systems comprising synchronous generators, multi-pulse rectifiers and motor drive loads, and to identify potential instability causes and optimize components size and control designs.

Hybrid AC-DC vehicular power system

Stability analysis of representative power system

Analytical estimation of large signal stability boundary