Fuzzy logic control of dual active bridge in solid state transformer applications

Solid state transformer (SST) enabled microgrid is the trend of microgrid. Most power electronic converters in the SST-enabled DC microgrid behave as constant power loads when their outputs are tightly regulated with little variations around the reference values. The constant power loads have a characteristic of negative incremental impedance, which may degrade the stability of SST-enabled DC microgrid if the dual active bridge (DAB) is not properly controlled. This paper proposes a Fuzzy Logic Controller (FLC) scheme for the DAB converter with constant power load. The proposed FLC is able to stabilize the dc-link voltage in the presence of significant variations in the load power. The proposed FLC is validated by simulation in MATLAB/Simulink for stabilizing the DAB converter with constant power load and resistive load. Simulation studies prove the FLC has satisfactoty performance. Precise regulation of the DC voltage are achieved by FLC, even in cases of load power change.