SMC-based power/voltage droop control in stand-alone DC microgrids

Most current droop control methods for DC microgrids are based on the voltage/current mode or the current/voltage mode. In this paper, an efficient droop controller for a stand-alone DC microgrid based on the power/voltage mode is proposed. Droop control is a multi-terminal control strategy, that is, several production units share the task of controlling the voltage value of the principal line of the microgrid. In this work, the generation unit equipped with droop control is assumed to be an inverting buck-boost (IBB) converter powered by a PV array. The sliding mode technique is adopted to manage the generated power as function of the voltage measured at the point where the converter is connected to the microgrid. The controller design is detailed through this manuscript considering a nonlinear averaged model which simulates the behaviour of the Buck-Boost converter. In addition, in order to reduce the number of the used sensors, the current through the filtering inductor of the DC-DC converter was estimated on the basis of a sliding mode observer. Finally, an experimental set-up was developed based on the IBB converter and the STM 32 control board with the aim of proving the proper operation of the proposed droop controller.