A Sliding Mode Control based stabilization solution for multiple Constant Power Loads with identical input filters interfaced with the DC bus of a ‘More Electric’ Aircraft

Abstract

The DC onboard microgrid of a More Electric Aircraft (MEA) comprises of multiple Point Of Load (POL) converters to cater to diverse loads at different voltage levels. Lightly damped LC filters are typically used at the inputs of these POLs to reduce the noise in the system. Any tightly regulated POL acts like a Constant Power Load (CPL) and exhibits negative incremental impedance. The interaction of a CPL with its input filter leads to instability in the form of voltage oscillations at the input filter capacitor. The problem becomes more complex with multiple loads when identical LC input filters are used for the parallel CPLs connected to the same DC bus. The linear active damping solutions fail to stabilize such a system. To overcome this issue, a nonlinear solution based on Sliding Mode Control (SMC) is proposed. A parabolic sliding surface is presented which successfully stabilizes the system. Stability analysis using Eigen value plots are demonstrated. Extensive analytical results and simulation results are shown to validate the effectiveness of the proposed scheme.