Higher Order Sliding Mode Observer Based Fast Composite Back stepping Control for HESS in DC Micro grids

Hybrid energy storage system (HESS) is effective to compensate for fluctuation power in renewables and fast fluctuation loads in DC micro grids. To regulate DC bus voltage, a power management strategy is an essential issue. In the meantime, the increasing integration of constant power loads (CPLs) in DC micro grids brings great challenges to stable operation due to their negative incremental impedance. In this paper, a fast composite back stepping control (FBC) method is proposed for the HESS to achieve faster dynamics, smaller voltage variations, and large signal stabilization. In the FBC method, a higher order sliding mode observer (HOSMO) is adopted to estimate the coupled disturbances. Furthermore, the FBC method is integrated with the droop control; so that the FBC-based decentralized power allocation (FBC-DPA) strategy for HESS in DC micro grids is developed. The proposed FBC method is designed based on the Lyapunov function to ensure its stability. Moreover, the design guidelines are provided to facilitate the application of the proposed method. Both simulation and experimental studies under different operating scenarios show that the proposed method achieves faster voltage recovery and smaller voltage variations than the conventional back stepping control method.

Keywords: Back stepping control, higher order sliding mode observer, hybrid energy storage system, dc micro grid.