Modelling and nonlinear control of Dual-Active Bridge converters for DC microgrids

This paper presents a novel control approach for a Dual Active Bridge (DAB) converter interconnecting a telecom isolated DC microgrid (IDCM) to a 380 V DC grid. A DAB converter is the ideal solution for this interconnection because it provides galvanic isolation, allows reversible power flow, and can operate with inherent soft switching, leading to high efficiency performance. The novel controller is based on Lyapunov's stability theory and adds integral terms to stabilize the IDCM nominal voltage. The new controller ensures the IDCM fast and stable transient response upon the connection of constant power loads (CPLs). In order to highlight the advantages of the new controller, comparisons using MATLAB/Simulink simulations are made with cascaded voltage/current linear controllers, their limitations being shown. Results point out that the novel controller is able to deal with the negative incremental resistance of CPLs, without the need of bulky stabilizing DC capacitors.