Distributed cooperative voltage mode control for DC-isolated microgrids powered by renewable energy sources

This article proposes a distributed model-based cooperative controller to improve voltage synchronization in DC-isolated microgrids that are powered by variable renewable energy sources. Based on the second-order voltage dynamics of dc-dc buck converters, we aim to develop an integral-based linear-quadratic regulator that synchronizes not only the output voltages but also their derivatives. It is necessary not only in reducing voltage ripples and their integrals but also in eliminating steady-state errors. This objective is achieved mainly by introducing a global performance index, which minimizes neighbor synchronization errors, apart from local synchronization errors, and thus transfers the interactions between the dc-dc buck converters from the physical layer to the communication layer. Furthermore, it is demonstrated that the proposed controller ensures global system stability according to the Lyapunov stability theory. Several simulations are made to show the effectiveness of the proposed technique in terms of voltage synchronization and stability, voltage ripple elimination, and voltage convergence speed when input voltage disturbances are present.