Design of an Adaptive Super-Twisting Sliding Mode Controller to Adjust Voltage in DC Microgrids with Constant Power Load

In this paper, a novel adaptive super-twisting sliding mode controller is proposed in order to adjust the voltage in DC microgrids. The DC microgrid contains supercapacitor, battery, and photovoltaic (PV) panels, in the presence of constant power load (CPL). Despite the existence of uncertainties and disturbances in DC microgrid dynamics, there is no need for prior knowledge of the upper bound of these unknown terms, and it is estimated by the proposed adaptation law. Furthermore, the effect of chattering in control signals is significantly reduced without the requirement of high-order time-derivative of the sliding surface. Accordingly, there is no need for additional sensors to measure time-derivative of states or calculate direct derivation of them that leads to the intensification of measurement noise. By utilizing the Lyapunov theory, the finite-time stability of the closed-loop system is guaranteed. Considering the aforesaid advantages of the proposed method, the practical implementation is simple and feasible. The simulation results show the efficiency of the presented method in comparison to the non-adaptive standard sliding mode and adaptive one for voltage control of DC microgrids in the presence of the variation of photovoltaic panel, battery, and supercapacitor voltages and load resistance.