Stabilization and energy management in a DC grid by a variable structure flatness-based controller

A variable structure flatness based controller achieving both stabilization and energy management in a DC grid is proposed in this paper. The grid connects through undamped LC filters, a voltage source, a storage device and a reversible load. It is shown that the energy management goals along with the reversibility of the load make the grid to behave as a variable structure system and that a fixed structure controller is not able to achieve the management goals. After identifying a flat output for the system, a variable structure controller resulting from switching between two "flat controllers" is proposed. The switching is driven by load power profile sign. The asymptotic stability of the grid under the switching controller results from the asymptotic stability of flat output feedback controllers along with "slow" switching assumption. Simulation results illustrate both the shortcoming of a fixed "flat controllers" and the effectiveness of the proposed approach.