Stability Studies of Critical DC Power System Component for More Electric Aircraft using μ Sensitivity

Abstract

In this paper an approach for stability analysis of power systems for "More Electric Aircraft" (MEA) using μ sensitivity is proposed. The application of the proposed appraoch is illustrated via a regulated buck converter as a typcial critical component in a power system. Due to the negative resistance at low frequencies the regulated buck converter could be unstable in combination with the input filter. A typcial regulated buck converter is first modelled in the simulation package Dymola. The model equations are transferred to Maple or Matlab with a Dymola toolbox and symbolically linearized at steady state conditions. For computing μ sensitivity it is necessary to get a Linear Fractional Representation (LFR) of the buck converter. This is done by using the enhanced LFR Toolbox 2.0. Finally, the μ sensitivity is computed with the Robust Control Toolbox 3.1.1 of Mathworks. Compared with other methods for small signal stability, e.g. Middlebrook criterion and Modal Analysis, the μ sensitivity approach gives a much more global and direct result for the influence of all components on stability.