Stability studies of critical DC power system component for More Electric Aircraft using μ sensitivity

In this paper an approach for stability analysis of power systems for "more electric aircraft" (MEA) using mu sensitivity is proposed. The application of the proposed approach is illustrated via a regulated buck converter as a typical 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 typical 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 mu 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 mu 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 mu sensitivity approach gives a much more global and direct result for the influence of all components on stability.