A switchable bilinear discrete-time modeling for the stability analysis of the digitally controlled three-phase dual active bridge dc-dc converter

Dual active bridge (DAB) converters have been used widely in the distributed energy system and storage equipment. However, the non-linearity of the power electronics due to the switching may cause stability problems. This paper discusses the dynamic properties and stability analysis of the three-phase DAB converter when operating under a digitally controlled closed loop. THE Three-phase DAB circuit state equation is different for low and high phase shift. Therefore a switchable model is proposed so that the state-space model can switch from one to another when the phase shift changes from low to high. A modified bilinear discrete-time model has been developed. The nonlinear properties of the three-phase DAB are studied under the variable control parameter. The effect of the circuit parameters like load resistance, filter capacitor, and leakage inductance on the stability is studied. The stability analysis is then later verified using simulation.