Adaptive sliding mode control for instability compensation in DC microgrids due to EV charging infrastructure

The electric vehicle (EV) chargers with the battery voltage/current regulated starts behaving as constant power loads. Therefore, the connection of EV chargers in dc microgrid reduces the stability margin of the system which can destabilize a dc microgrid. Further, the limit on charging power supplied by the EV charger to the battery increases the charging time of the battery. The main aim of this paper is to compensate the instability caused due to EV chargers in a dc microgrid including renewable energy sources like solar photovoltaic (PV) sources which are interfaced to dc-bus using dc–dc boost converters. For stabilization of this system, an adaptive sliding mode control (ASMC) is synthesized for dc–dc boost converters feeding constant power load. The proposed controller modifies its gain in order to maintain sufficient stability margin during large step variation in load demand. The adaptive variation ensures a high robustness against wide changes of the charging power demand and does not require any prior knowledge about the bounds of the system. Further, the stability analysis of the proposed ASMC using Lyapunov method guarantees the finite time convergence of sliding surface and asymptotic convergences of converter state variables. The efficacy of the proposed controller is validated with the help of results captured using Controller Hardware-in-the-Loop (CHIL) and experimental setup. These results show the effectiveness of practical implementation of the proposed controller.