Robust Feedback Linearization Control for DAB Converter feeding a CPL

Abstract

Cascaded converters are used to satisfy the different voltage levels that loads need. Instability problems in cascaded systems may occur due to the interaction of Point-of-Load (POL) converters. POL converters exhibit the important characteristic of almost-perfect regulation at the output terminals independent of the input perturbations. However, such characteristic reflects at the input terminal as a constant power load (CPL). CPL exhibits incremental negative resistance behavior causing undesired oscillations and a high risk of instability in interconnected converters. In this paper, the cascaded converter system consists of a Dual Active Bridge (DAB) DC-DC converter that maintains a regulated DC voltage on the intermediate bus and a POL DC-DC Buck converter that acts as a CPL. Aiming to ensure system stability and effectively mitigate oscillations effects in a cascaded system, this paper proposes a Robust Feedback Linearization Control to regulate the intermediate DC bus voltage. Simulation tests are performed by using a MATLAB/Simulink simulator to show the robustness and effectiveness of the proposed controller. The simulation results show that the proposed control approach ensures robust control performance and stability with a minor performance degradation compared to a Robust Control approach, Feedback Linearization Control approach, and Classical Control approach.