Iteratively Sustained Sliding Mode Control based energy management in a DC Microgrid

Renewable energy sources (RES) are becoming potential reserves in power systems owing the capability of generation at customer ends by operating as a Microgrid. An efficient controller is indispensable for a stable and reliable power supply in the Microgrid premises. In this work, we propose an Iteratively Sustained Sliding Mode Controller (ISSMC) working in a two-level hierarchical architecture to respond appropriately for continuous tracking of uncertainties in a DC Microgrid. The DC Microgrid comprises of Solar Photovoltaic (PV) array source, battery-supercapacitor (SC) based hybrid energy storage system (HESS) and dynamic loads coupled at a DC-link. The proposed controller appropriately tracks the set points provided by an energy management algorithm at secondary level with the objective of power balance and constant voltage maintenance at the DC-link node. During uncertain conditions such as fluctuating irradiance pattern, variations in load demand and occurrence of faults within the microgid, the proposed controller retains the error signal over the sliding bounds by iteratively sustaining the sliding regime response of the Sliding Mode Control (SMC) law using Iterative Learning Control (ILC) method. The simulations were performed to evaluate the performance of the proposed controller under different operating conditions such as the step variations in irradiance and load demand profile. The controller response is recorded to analyze its steady-state operation, tracking accuracy, and effective cooperation of sources for energy management. Also, the effectiveness to preserve the sliding regime is demonstrated during power disturbances on the demand side of the DC Microgrid involving constant power loads and AC loads. It was found that the proposed controller provided adequate tracking accuracy and fast restoration to the steady state under all the operating conditions. To further emphasize the effectiveness of the controller, the simulations were also conducted for a real-time irradiance pattern. Furthermore, the controller behavior was also evaluated in the controller hardware-in-the-loop (C-HIL) test setup using a microcontroller unit TMS320F28379D Delfino Launchpad.