Super-Twisting Sliding Mode Control of DC Microgrids Involving Renewable Sources and Storage Devices

Abstract

This paper describes the application of chattering-free super-twisting sliding mode controllers to the control of DC electric microgrids encompassing renewable sources of energy and storage devices. The microgrid is composed of a photovoltaic source, a super capacitator and a battery set aimed at providing power when the renewable source is not available. These components are connected to a bus by means of DC converters, being each one controlled by the corresponding duty cycle. Three control commands are thus needed to be designed. Moreover, the controller of the DC converter connecting the super capacitor to the bus is designed as a combination of super-twisting and backstepping techniques. This approach combines the simplicity of backstepping designs along with the robustness properties of super-twisting sliding mode controllers. The proposed approach can guarantee the regulation of system’s outputs, namely the tracking of the maximum power point, the management of the power provided/absorbed by the battery and the voltage in the bus regardless the presence of potentially time-varying resistive loads. A sensitivity analysis is performed to highlight the effect of control parameters in the closed-loop performance while the effect of time-varying loads and parametric uncertainty is also assessed.