Composite Sliding Mode Control for Converters With Unknown Constant Power Load

DC microgrids have drawn extensive research interests. It is of great significance to obtain fast voltage dynamics and large signal stability when feeding constant power loads (CPLs). In this paper, an active stabilization design strategy is proposed for DC-DC converters with unknown CPLs, which is based on sliding mode control (SMC). First, generalized proportional-integral (GPI) observers are proposed to accurately reconstruct the multiple time-varying disturbances. Second, a composite controller is constructed by integrating disturbance compensations. Moreover, to promote the dynamic responses, a finite-time convergent SMC approach is further developed in this paper. Finally, both simulation and experimental comparisons are illustrated to demonstrate the effectiveness of the presented controller. The proposed approach is characterized by higher voltage tracking accuracy, better dynamic properties and stronger disturbance rejection ability even in the presence of significant load power and supplied voltage variations.