Fast Composite Backstepping Control for CPLs with Energy Storage Systems in DC Microgrids

Energy storage systems (ESSs) are effective in compensating for fast-fluctuating loads in dc microgrids. The inherent non-linearity of constant power loads (CPLs), particularly their manifestation of negative incremental resistance characteristics, introduces significant challenges in maintaining adequate damping ratios and compromising stability boundaries within power electronic systems. These issues necessitate the development of appropriate strategies for an efficient implementation framework in dc microgrids. In this paper, we first present an extended disturbance observer designed to estimate the instantaneous currents associated with the uncertain, time-varying dynamics of CPLs. The designed observer improves the speed of state estimation and simultaneously strengthens the system’s resilience to fluctuations in physical parameters. Building on the estimated load power, an efficient composite backstepping control approach is then proposed, which guarantees overall grid stability and enables convergence to the target dc bus voltage. To ensure the stability of the designed control strategy, a strict Lyapunov theory-based method is utilized. In the end, simulation tests across multiple conditions are carried out to demonstrate both the effectiveness and practical applicability of the developed approach.